MWCNT-loaded MoS₂ nanoflower-modified electrodes as efficient catalysts for direct glycerol fuel cells†

Yueli Wang^a, Yanhong Mo^a, Qinghong Zhou^a, Xiaoyong Jin*^a, Yonglei Xing^a, Beibei Kou^a, Juan Peng^a and Gang Ni^b
aState Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering, School of Chemistry and Chemical Engineering, Ningxia University, Yinchuan 750021, China. E-mail: jinxy588@163.com
^bNingxia Key Laboratory of Green Catalytic Materials and Technology, College of Chemistry and Chemical Engineering, Ningxia Normal University, Guyuan 756000, China

First published on 21st July 2025

---

---

1. Introduction

In the context of population growth and resource shortage, the development of clean and renewable energy has become a key issue for sustainable development.^1,2 As a new electrochemical device, fuel cells catalyze the electrochemical reaction between fuels and oxidants to achieve efficient conversion of chemical energy to electrical energy and combine high efficiency with environmental advantages.^3,4 Glycerol is a key by-product in the industrial production process of biodiesel, which has significant resource advantages. According to statistics, the yield of glycerol in the preparation of biodiesel can reach 10% (mass ratio).⁵ In response to the problem of excess glycerol in the traditional biodiesel industry, direct glycerol fuel cells (DGFCs) can directly convert glycerol chemical energy into electrical energy through the catalytic oxidation reaction and simultaneously achieve waste resourcing and clean energy production. Its theoretical energy density of 6.26 kWh kg⁻¹ is better than that of methanol (5.54 kWh kg⁻¹), and it offers advantages such as wide availability, low cost, high safety, and adaptability to acid and alkali media environments,^6,7 which can form a complete electron transfer chain during glycerol oxidation.

The core working mechanism of direct glycerol fuel cells is based on the electrochemical oxidation of glycerol molecules at the anode and the oxygen reduction reaction at the cathode. At the anode, the glycerol molecules undergo a multi-electron transfer oxidation reaction in the presence of a specific catalyst, which can reach a theoretical value of up to 14-electron process for complete oxidation under alkaline conditions (C₃H₈O₃ + 14OH⁻ → 3CO₂ + 11H₂O + 14e⁻), whereas at the cathode a typical oxygen reduction reaction occurs (O₂ + 2H₂O + 4e⁻ → 4OH⁻). It is worth noting that the anodic oxidation process involves complex C–C bond breaking, which places stringent demands on the performance of the electrode materials.⁸ In recent years, transition metal disulfides (TMDs) have demonstrated significant advantages in the field of electrocatalysis due to their unique two-dimensional layered structure, tunable electronic properties, and abundant active sites.⁹ In particular, the wide range of applications of molybdenum disulfide (MoS₂) materials in supercapacitors,¹⁰ batteries,¹¹ and hydrogen-evaporation reactions (HERs)¹² have made them one of the most popular nanomaterials in the energy field. In terms of the structural design of the materials, the electrochemical properties of the prepared materials can be significantly enhanced by constructing a multidimensional composite system. He¹³ et al. prepared a honeycomb-shaped Pd/MoS₂/NiF self-supported electrode. Compared with the Pd/NiF electrode, the Pd/MoS₂/NiF electrode has a higher onset potential, stronger electrocatalytic activity and better long-term stability. A direct borohydride–hydrogen peroxide fuel cell assembled with Pd/MoS₂/NiF as the anode and cathode could achieve an excellent peak power density of 80.02 mW cm⁻² at 125 mA cm⁻² and also had excellent operational stability. Yang¹⁴ et al. prepared MoS₂/Co₉S₈/Ni₃S₂ loaded on NFs. The material has a controllable morphology and exhibits excellent bifunctional electrocatalytic performance for both the electrocatalytic hydrogen precipitation reaction and oxygen evolution reaction (OER) over the full pH range. This multicomponent synergistic strategy sheds important light on the catalyst design for complex multistep oxidation reactions in the DGFC.

In the process of optimizing the anodic catalytic system for DGFCs, the selection of high-performance catalyst carriers is a key component to improve the power density of the cell. It has been shown that the carrier material can significantly enhance the utilization of catalytic active sites through electronic modulation.¹⁵ Ideal catalyst carriers need to satisfy the following characteristics: a high specific surface area to provide sufficient active site loading space, excellent electrochemical stability to withstand the strong oxidative environment of the fuel cell, and high electrical conductivity to construct an efficient charge transport network.¹⁶ Under these conditions, carbon-based materials have become the choice of carrier materials by virtue of their unique structural advantages, among which carbon nanotubes (CNTs) have attracted much attention due to their excellent electrochemical stability and excellent electrical conductivity. As a typical carbon-based carrier, MWCNTs are widely used as conductive carriers for catalysts due to their relatively large specific surface area, rich pore structure and good stability.¹⁷ Lotfi¹⁸ et al. prepared Ni-MoSe₂/f-MWCNT composites. The results showed that the prepared material displayed an onset potential of 0.33 V in an alkaline solution containing 1 M methanol, and showed excellent stability, retaining 90% methanol oxidation reaction (MOR) activity even after 8000 s. Monfared¹⁹ et al. investigated CuNi₂O₄ and CuNi₂O₄/MWCNT nano catalysts for MOR and ethanol oxidation reaction (EOR) applications. A comparison of the performance of the two nano catalysts revealed that the electrocatalytic performance of CuNi₂O₄/MWCNTs was much higher than that of CuNi₂O₄. Thus, it appears that carbon nanotubes increase the active electrochemical surface and enhance the electrical conductivity, which improves and facilitates the EOR and MOR processes. Mohsen²⁰ et al. prepared MnO₂/NiO/MWCNT composites that showed a lower onset potential than MnO₂/NiO in the electrooxidation of methanol and ethanol, due to the synergistic effect of adding MWCNTs to the catalyst structure. The significant performance enhancement observed when MWCNTs are incorporated into catalyst structures highlights their critical role in electrocatalysis. This strategy of combining active sites with conductive supports is not only applicable to MWCNTs but also encompasses a broader family of emerging two-dimensional (2D) materials. MXene materials,^21–24 which possess intrinsic metallic conductivity, rich surface chemistry, and tunable layered structures, along with covalent organic frameworks (COFs)²⁵ renowned for their highly ordered porous structures, crystallinity, and designable functional groups, demonstrate immense potential in facilitating charge transfer and providing ample active sites for various electrochemical reactions. Therefore, this study was planned to design a MWCNT-loaded MoS₂ nanoflower-modified electrode, which introduced abundant sulfur vacancies and edge-active sites into the nanoflower structure by modulating the defect engineering of MoS₂,²⁶ thus significantly enhancing the adsorption activation capacity for glycerol molecules; meanwhile, the three-dimensional conductive network of MWCNTs not only provided high specific surface area support for MoS₂ nanoflowers, but also accelerated the electron transport during the reaction through interfacial coupling. In the present study, we have prepared nanoflower-like MoS₂ grown on MWCNTs and have innovatively used this material for DGFCs.

By using a simple one-step hydrothermal method to prepare MoS₂/MWCNT materials, the preparation process is easy and avoids the use of precious metal materials, which is less costly and more environmentally friendly in comparison. Corresponding XRD, SEM, TEM and XPS assays confirmed the successful preparation of the materials. MoS₂ nanoflowers were uniformly grown on the surface of MWCNTs, and this unique morphology exposed both abundant edge active sites and established continuous electron conduction channels. The catalytic activity of the glycerol oxidation reaction at the MoS₂/MWCNT electrode was investigated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The results showed that the obtained electrocatalysts possessed higher current density, smaller onset potential and better GOR stability, and the constructed H-type glycerol fuel cell had high energy density. This work provides a new idea for the development of efficient and stable anode catalysts for direct glycerol fuel cells, especially in solving the difficult problem of regulating the complex reaction paths of multi-electron transfer of glycerol molecules, which gives an effective method.

2. Experimental

2.1 Materials

Nickel foam (0.5 × 200 × 297 mm) was purchased from Shenzhen Nanotech Port Co., Ltd. HCl (AR), CH₃COCH₃ (AR, 99.5%), CH₄N₂S (AR), Na₂MoO₄·2H₂O (AR), and CH₃CH₂OH (AR) were purchased from Sinopharm Group Chemical Reagents Co., Ltd. C₃H₈O₃ (AR, 99%), C₃H₈O (AR), and KOH (AR) were purchased from Sinopharm Group Chemical Reagents Co., Ltd. MWCNTs (AR, 99%) were purchased from Shenzhen Nanotech Port Co., Ltd. Pt/C (TANAKA, TEC10E20E, the content of Pt is 20%) was purchased from Suzhou Sinero Technology Co., Ltd. Nafion solution (5 wt%) was purchased from Tianjin IncoleUnion Technology Co., Ltd. Deionized water (>18 MΩ) was obtained from an ultrapure water system (Milli-Q Academic).

2.2 Characterization

The crystalline phases of the synthesized samples were analyzed via X-ray diffraction (XRD, Bruker D8 Advance) with Cu Kα radiation at 40 kV and 40 mA. The morphology, structure, and grain size of the samples were characterized using scanning electron microscopy (SEM, Hitachi Regulus 8100) and transmission electron microscopy (TEM, FEI Talos F200x). X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific Nexsa) was utilized to examine the chemical states, surface elemental composition, and molecular structure of the samples. Electrochemical measurements were conducted at room temperature using a Princeton electrochemical workstation (DH70000, Jiangsu Donghua Analytical Instruments Co., Ltd). A standard three-electrode configuration was employed, with the prepared MoS₂/MWCNT catalyst serving as the working electrode, a platinum plate as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode.

2.3 Preparation of the MoS₂/MWCNT electrode

The MoS₂/MWCNT composite was synthesized via a one-step hydrothermal method. Initially, 12.5 mg of MWCNTs were dispersed in 30 mL of deionized water and magnetically stirred at room temperature for 30 min. Subsequently, 242 mg of sodium molybdate dihydrate and 304 mg of thiourea were added, followed by 30 min of ultrasonication to achieve a homogeneous dispersion. The resulting solution was transferred to a 50 mL Teflon-lined stainless steel autoclave and maintained at 190 °C for 30 h. After cooling to room temperature, the product was repeatedly washed with distilled water and ethanol. The resulting MoS₂/MWCNT material was obtained after drying in a vacuum oven at 60 °C for 24 h. The MoS₂ synthesis followed a similar procedure, with sodium molybdate dihydrate and thiourea dissolved in deionized water. Under stirring, 12 M HCl was added dropwise to the mixed solution, adjusting the pH to less than 1. The solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave and heated at 200 °C for 24 h.

Prior to utilization, the nickel foam undergoes pretreatment. Initially, the nickel foam is sectioned into rectangular electrode sheets measuring 2.0 × 1.0 cm². These are then immersed in a 3 M hydrochloric acid solution and sonicated for 30 min. Subsequently, they undergo sonication in acetone for an additional 30 min, followed by sonication in ethanol for 1 h, and finally, sonication in deionized water for 1 h. Post-sonication, the samples are rinsed three times with deionized water and dried overnight in a vacuum drying oven, yielding the pretreated nickel foam.

For electrode fabrication, 2 mg of the prepared material powder is introduced into a vial, along with 1 ml of ethanol, 1 ml of deionized water, and a 5 wt% Nafion solution. This mixture is then sonicated for 30 min. A 100 μL aliquot of the resulting ink is drop-cast onto a 1.0 × 1.0 cm² area of the nickel foam, resulting in the MoS₂/MWCNT electrode. By substituting the electrode materials with MWCNTs or MoS₂, the corresponding electrodes can be obtained.

2.4 Preparation of the Pt/C electrode

2 mg of Pt/C powder was weighed in a tube, and 150 μL of water, 150 μL of isopropanol, and 5 wt% Nafion solution were added to the tube, subjected to sonication for 30 min to make ink, dropping it onto carbon paper in batches; it was then placed in a vacuum oven at 60 °C, and dried overnight; the prepared Pt/C electrode was obtained.

2.5 Construction of a direct glycerol fuel cell

An H-type dual chamber fuel cell was constructed by using the MoS₂/MWCNT material prepared as mentioned in section 2.3 as the anode material with a catalyst loading of 0.1 mg cm⁻² and an anode electrolyte of 1 M KOH + 0.1 M glycerol. The Pt/C material was used as the cathode catalyst with a catalyst loading of 2 mg cm⁻², and the cathode electrolyte consisted of 1 M KOH saturated with oxygen. An anion exchange membrane was used to separate the cathode and anode chambers. The polarisation curves of the fuel cell were measured by linear scanning voltammetry and the power density was calculated.

3. Results and discussion

3.1 Characterization of the MoS₂/MWCNT composite

The crystal structures of the MoS₂/MWCNT composites were systematically characterised using X-ray diffraction. As shown in Fig. 1, the diffraction peaks located at 14.1°, 32.8°, and 58.1° in the XRD patterns of the composites match perfectly with the (002), (100), and (110) crystal planes of the standard card of hexagonal-phase MoS₂ (PDF# 37-1492). It is noteworthy that MWCNTs present a sharp (002) crystal plane diffraction peak at 26.3° (PDF# 26-1079), and its narrower half-height width reflects that the carbon nanotubes have a good degree of graphitisation. By comparing the standard cards, it can be found that the characteristic peak positions of MoS₂ in the composites are not significantly shifted, indicating that the intrinsic crystal structure was not destroyed during the composite process, and the coexistence of the (002) peak of MWCNTs with the (100) peak of MoS₂ confirms the successful composite of the two phases. In addition, the diffraction signals of other impurity phases were not detected in the plots, which further verified the successful preparation of the composites.

SEM was used to characterise and analyse the micro-morphology of the materials. The SEM images of multi-walled carbon nanotubes and molybdenum disulphide/multi-walled carbon nanotube composites are illustrated in Fig. 2. The observations showed that the samples had clean surfaces, and no impurity attachment was found. As shown in Fig. 2d and e, MoS₂ exhibits typical rosette-like morphological features, and these nanoflower-like structures are encapsulated by the network of MWCNTs and uniformly loaded on the surface of MWCNTs, which are intertwined to form a stable three-dimensional mesh-like composite structure. This morphological feature fully confirms the successful preparation of MoS₂/MWCNT composites.

Fig. 2c demonstrates the high-resolution transmission electron microscopy (HRTEM) characterisation results of the MoS₂/MWCNT composites. Two sets of characteristic lattice fringes can be clearly observed from the HRTEM images, the fringes with a crystallographic spacing of 0.625 nm correspond to the (002) crystallographic plane of MoS₂, while the fringes with a crystallographic spacing of 0.344 nm are attributed to the (002) crystallographic plane of MWCNTs, and this result is consistent with the X-ray diffraction analysis. As shown in Fig. 2f, the micro-morphological features of MoS₂/MWCNTs in the TEM image are highly consistent with the results observed from the SEM maps, which further confirms the reliability of the material structure. It can be observed through the elemental distribution mapping plots in Fig. 2h–j that the Mo and S elements show uniform distribution characteristics on the nanoflower-like structure, while the MWCNTs are tightly encapsulated around the MoS₂ nanoflower, forming good heterogeneous interfacial contact. This unique structure not only facilitates electron transport but also provides abundant active sites for the electrocatalytic reaction. The above characterisation results confirmed the successful preparation of the MoS₂/MWCNT composite electrocatalysts from multiple dimensions, such as microstructure, lattice features and elemental distribution, which provided a good structural basis for their excellent electrocatalytic performance.

X-ray photoelectron spectroscopy was used to deeply analyse the elemental composition, valence and bonding of the MoS₂/MWCNT composite catalyst. The full spectrum analysis shown in Fig. 3a reveals that the characteristic signals of Mo 3d, S 2p, C 1s and O 1s are mainly present on the surface of the material, where the presence of the elemental O is due to the unavoidable oxidation of the sample surface. In the C 1s spectrum of Fig. 3b, it can be observed that the characteristic peaks located at 284.8 eV and 286.2 eV are attributed to C–C and C–O/C–S bonds, respectively.²⁷ Among them, the presence of the C–S bonds confirms the strong electronic coupling between MoS₂ and carbon tubes. In the S 2p spectrum shown in Fig. 3c, three characteristic peaks can be analyzed, the characteristic peaks located at 161.8 eV and 163.1 eV belong to S 2p_3/2 and S 2p_1/2, respectively. Among them, the peak located at 164.3 eV is attributed to the C–S bond, which is a chemical bond present between MoS₂ and MWCNTs. Fig. 3d shows the XPS spectra of Mo presenting four peaks, of which the two main peaks at 228.9 eV and 232.0 eV are attributed to the 3d_5/2 and 3d_3/2 of elemental Mo,²⁸ respectively, and the two peaks at 232.9 eV and 235.3 eV due to oxidation in air. They are attributed to Mo⁶⁺ 3d_5/2 and 3d_3/2, respectively, and the peak at 226.2 eV is attributed to S 2s.

3.2 Electrochemical performance of anodic electrocatalysts

As shown in Fig. 4a, a three-electrode system was constructed for electrochemical testing, in which the MoS₂/MWCNT composite was used as the anode, a platinum sheet electrode as the cathode, and SCE as the reference electrode, and all the electrochemical tests were carried out at the Princeton electrochemical workstation. As shown in Fig. 4a, the electrocatalytic performance of MoS₂/MWCNTs in alkaline electrolyte solutions with or without glycerol was tested using linear scanning voltammetry (LSV) for comparison, and the current density of MoS₂/MWCNTs in the electrolyte solution containing glycerol (410.75 mA cm⁻²) was much higher than that of the electrolyte solution without glycerol (110 mA cm⁻²) when the potential was 0.8 V (vs. SCE). The current density in the electrolyte solution containing glycerol fully confirmed the excellent catalytic activity of MoS₂/MWCNT electrocatalysts for the glycerol oxidation reaction (GOR). Fig. 4b compares the different potential values corresponding to the same current density values, and it can be clearly observed that the potential values of the glycerol-containing systems are lower than those of the non-glycerol-containing systems at the same current density values. And the difference in the potential becomes more and more obvious as the value of the current density increases. It indicates that the MoS₂/MWCNT electrocatalysts have smaller onset oxidation potentials and higher current density values in the glycerol-containing system.

Fig. 4c compares the performance of electrodes modified with different materials in a 1 M KOH + 0.1 M glycerol electrolyte, and it can be observed that the current density values of both MoS₂/MWCNTs (410.75 mA cm⁻²) are higher than those of MoS₂ (271.4 mA cm⁻²) and MWCNTs (190.7 mA cm⁻²) at 0.8 V. Moreover, through Fig. 4c, it can be clearly observed that MoS₂/MWCNTs have the lowest onset oxidation potential among the three different materials. In summary, it indicates that MoS₂/MWCNTs have the lowest onset oxidation potential and the highest current density value for the glycerol oxidation reaction, suggesting that the composites have the optimal reaction kinetics, which is mainly attributed to their enhanced electron transport capacity and abundant active sites. The Tafel slope values corresponding to different materials were fitted according to the linear scanning voltammetry curves in Fig. 4d, and the reaction kinetics were evaluated during the reaction process. The Tafel slope values were 300.91 mV dec⁻¹ for the MoS₂ material and 219.32 mV dec⁻¹ for the MWCNT material, both of which were much larger than that of MoS₂/MWCNTs (104.74 mV dec⁻¹). The results indicate that the MoS₂/MWCNT electrocatalyst has the fastest reaction kinetics for the glycerol oxidation reaction.

To further investigate the kinetics of the glycerol oxidation reaction of the obtained catalysts, electrochemical impedance spectroscopy was performed in an electrolyte solution containing 1 mol L⁻¹ KOH and 0.1 mol L⁻¹ glycerol. The equivalent circuit shown in Fig. 5a was fitted, where the semicircle diameter represents the charge transfer resistance (R_ct), which can be used to evaluate the electrochemical reaction rate. From the observation in Fig. 5a, it can be obtained that the charge transfer resistance of the system containing glycerol (2.532 Ω) is smaller compared to the system without glycerol (17.98 Ω), indicating higher reaction kinetics during the glycerol oxidation reaction.²⁹ The electrochemical impedance spectra of MoS₂, MWCNTs and MoS₂/MWCNTs in 1 M KOH and 0.1 M glycerol electrolyte solutions were investigated in Fig. 5b and the test results are shown in Table 1, where it can be observed that there is not much difference in the R_ct values of the electrocatalysts for MoS₂ (20.68 Ω) and MWCNTs (20.37 Ω), but the R_ct value of the MoS₂/MWCNTs (2.532 Ω) is much smaller than those of MWCNTs and MoS₂, which indicates that the obtained composite MoS₂/MWCNT electrocatalysts have faster reaction kinetics and are more favourable for the glycerol oxidation reaction.

---

The electrochemical specific surface area (ECSA) is likewise an important parameter for evaluating the performance of the catalysts, and its value can be characterized by the capacitance of the double electric layer (C_dl) value. As shown in Fig. 6a–c, the cyclic voltammetry curves of MoS₂/MWCNTs, MoS₂, and MWCNTs in the non-Faraday interval of −0.2 to −0.1 V with a sweep rate of 20–100 mV s⁻¹ are demonstrated. Based on the linear relationship between the current density difference and the sweep speed shown in Fig. 6d, the C_dl values of the three were calculated to be 0.73 mF cm⁻² (MoS₂/MWCNTs), 0.68 mF cm⁻² (MoS₂), and 1.02 mF cm⁻² (MWCNTs), respectively. It is noteworthy that although the MWCNTs exhibited the largest C_dl value, corresponding to the largest electrochemical specific surface area, the catalytic ability of the MoS₂/MWCNT composites demonstrated a significant advantage. This phenomenon can be attributed to the synergistic mechanism of MoS₂ and MWCNTs. On the one hand, the three-dimensional conductive network system constructed by MWCNTs can effectively enhance the charge transfer efficiency, while at the same time, the high specific surface area of MWCNTs provides the structural support for the homogeneous loading of the actives,³⁰ on the other hand, the sulfur atoms exposed at the edges of MoS₂ nanoflowers act as the high-activity catalytic sites, whose catalytic activity is significantly better than that of MWCNTs. The synergistic effect of the two enabled the composites to maintain a high density of active sites and significantly enhance the overall reaction kinetics of the catalysts by optimizing the electron transport paths, thus overcoming the limitations of single-component materials in terms of specific surface area or intrinsic activity.

As shown in Fig. 7, the electrocatalytic oxidation behavior of MoS₂/MWCNT catalysts under different glycerol concentration conditions was investigated in this study. Using a standard three-electrode test system with the MoS₂/MWCNT-modified electrode as the working electrode and the saturated calomel electrode and platinum sheet as the reference electrode and counter electrode, respectively, the electrocatalytic response was investigated by linear scanning voltammetry in a 1 M KOH electrolyte system in the range of 0.01–0.5 M glycerol concentration. The test conditions were controlled with a scan rate of 50 mV s⁻¹ to ensure comparability of the kinetic parameters. It is evident from Fig. 7a that the glycerol concentration of 0.1 M has the lowest onset potential and the highest current density value among the five different glycerol concentration conditions compared. Fig. 7b demonstrates the highest current density values under the conditions of different concentrations of glycerol, and it can be observed that the current density increases linearly with increasing glycerol concentration in the concentration interval of 0.01–0.1 M, indicating that the reaction is controlled by the mass transfer process at this stage; when the concentration is more than 0.1 M, the catalytic activity instead shows a significant decreasing trend. Despite the continuous increase of the reactant concentration, the catalytic performance showed a significant decay. This nonlinear pattern of change suggests that there exists an optimal value of reactant concentration for the effective utilization of the catalyst active sites; when the glycerol concentration is lower than 0.1 M, the concentration limits the reaction process, whereas, when the glycerol concentration is too high, the performance may be degraded due to the accumulation of intermediates or the blockage of active sites on the catalyst surface. Therefore, 0.1 M was identified as the most suitable concentration condition for the electrochemical oxidation of glycerol in this catalytic system.

As stability is likewise an important index for evaluating the performance of catalysts, in this study, a fixed three-electrode system was constructed, in which the MoS₂/MWCNT electrode was the working electrode, the saturated calomel electrode was the reference electrode, and the platinum sheet was the counter electrode. The stability of the MoS₂/MWCNT electrode was investigated using chronoamperometry. From the chronoamperometry test in Fig. 8a, it can be clearly concluded that the current density value of the MoS₂/MWCNT electrode decreases as the test time becomes longer. This leads to two possible conclusions, firstly, the stability of the MoS₂/MWCNT electrode is not good, which leads to the decreasing current density value as the test time increases, and secondly, the glycerol content in the solution decreases, and the current density value output from the three-electrode system decreases as a result of the decreasing concentration of glycerol during the glycerol oxidation reaction. In order to further discuss the reasons for the decreasing current density values, the experimental procedure was changed to replace the electrolyte solution with a brand new one every 1800 s under the same conditions, as shown in Fig. 8b, and after replacing the new electrolyte solution, the current density values could return to the values of the initial test. After 20 repeated tests, the average retention of the current density of MoS₂/MWCNT composites was 96.95% after each change of the electrolyte solution. XRD testing was performed on the material before and after the reaction, as shown in Fig. 9. The characteristic peak positions in the XRD patterns before and after the reaction did not shift, further proving the stability of the material. Therefore, it is concluded that in Fig. 8a, the decreasing current density value of the MoS₂/MWCNT electrode as the test time becomes longer is due to the decreasing concentration of glycerol as the reaction proceeds, and the MoS₂/MWCNT electrocatalysts still have good stability after repeated glycerol oxidation reactions.

3.3 Construction of the direct glycerol fuel cell

Based on the above conclusions, it can be seen that MoS₂/MWCNT have good catalytic activity towards glycerol. Meanwhile, Pt/C was selected as the cathode catalyst and applied to the ORR. Therefore, in this study, a two-electrode system was constructed, with MoS₂/MWCNT as the anode material, Pt/C as the cathode material, and an anion-exchange membrane was used to isolate the cathode chamber from the anode chamber, forming an H-type glycerol/oxygen fuel cell.

Fig. 10a shows the schematic diagram of the constructed direct glycerol fuel cell. The output performance of the fuel cell was tested as shown in Fig. 10b, where the black curve is the polarization curve, and an open-circuit voltage of 0.35 V is obtained for the constructed H-type glycerol fuel cell. The power density curve of the cell (in red) can be calculated and fitted based on the calculation of the multiplication of the values of the cell voltage and the current density in the polarization curve, and it is understood from the figure that the maximum power density is 0.67 mW cm⁻². Table 2 summarizes the reported performances of a direct glycerol fuel cell and compares them with the present study. It can be intuitively seen that the direct glycerol fuel cell constructed in the present study, with a low catalyst loading (0.1 mg cm⁻²) at room temperature, was prepared with a MoS₂/MWCNT electrocatalyst that has high electrocatalytic performance and demonstrated good power density values in the constructed direct glycerol fuel cell.

---

4. Conclusion

In this study, MoS₂/MWCNT electrodes with good catalytic activity were prepared by a one-step hydrothermal method. The structure of MWCNTs tightly encapsulated around MoS₂ nanoflowers not only facilitates the electron transport but also provides abundant active sites for the electrocatalytic reaction, which improves the charge transfer rate. The prepared materials can achieve efficient catalysis of glycerol oxidation under alkaline conditions. The assembly of an H-type glycerol fuel cell with the MoS₂/MWCNT material as the anodic catalyst and Pt/C as the cathodic catalyst can not only achieve efficient catalytic oxidation of glycerol but also improve the performance of the glycerol fuel cell. The constructed H-type glycerol fuel cell has a high-power density of 0.67 mW cm⁻² at a potential of 0.16 V. In summary, MoS₂/MWCNTs have the characteristics of simple synthesis, good electrocatalytic performance and high stability, and have broad application prospects in DGFCs.

Author contributions

Yueli Wang: methodology, experimental, and writing – original drafts. Yanhong Mo: data curation and editing. Qinghong Zhou: formal analysis and original drafts. Xiaoyong Jin: conceptualization, resources, revision, and supervision. Yonglei Xing: revision and supervision. Beibei Kou: formal analysis and editing. Juan Peng: methodology and writing. Gang Ni: resources and supervision.

Conflicts of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

All the data generated in this study are reflected in this article. For more detailed information regarding the experiment, please contact the corresponding author at jinxy588@163.com.

Acknowledgements

This work was financially supported by the University Research Projects of Department of Education of Ningxia (NYG2024010), the Central Guidance on Local Science and Technology Development Special Fund of Ningxia (2024FRD05064), and the Natural Science Foundation of Ningxia (2024AAC02001).

References

1. K. Lim, A. Lee, V. Atanasov, J. Kerres, S. Adhikari, S. Maurya, E. J. Park, L. Delfin, J. Jung, F. Cy, I. Matanovic, J. Jankovic, H. Jia and Y. S. Kim, Nat. Energy, 2021, 7, 248–259 CrossRef .
2. L. Huang, S. Zaman, X. Tian, Z. Wang, W. Fang and B. Y. Xia, Acc. Chem. Res., 2021, 54, 311–322 CrossRef CAS PubMed .
3. A. Molina Villarino, J. L. Rowell, D. Yoon, Q. Li, Y. Jia, Z. Shi, J. Soto, J. Koldobskiy, D. A. Muller, R. D. Robinson and H. D. Abruña, ACS Catal., 2024, 14, 5436–5443 CrossRef CAS .
4. W. Gong, Z. Jiang, R. Wu, Y. Liu, L. Huang, N. Hu, P. Tsiakaras and P. K. Shen, Appl. Catal., B, 2019, 246, 277–283 CrossRef CAS .
5. L. R. Kumar, S. K. Yellapu, R. D. Tyagi and X. Zhang, Bioresour. Technol., 2019, 293, 122155 CrossRef CAS PubMed .
6. K. Zakaria, M. McKay, R. Thimmappa, M. Hasan, M. Mamlouk and K. Scott, ChemElectroChem, 2019, 6, 2578–2585 CrossRef CAS .
7. P. N. A. Othman, N. A. Karim and F. Rusydi, Fuel Cells, 2024, 25, e202300238 CrossRef .
8. L. Pei, S. Xie, H. Guo, X. Li, H. Xie, Z. Tang, G. Han, Z. Xia, M. Li and H. Liu, Chem. Eng. J., 2024, 483, 149113 CrossRef CAS .
9. M. Ranjani, N. Senthilkumar, G. Gnana Kumar and A. Manthiram, J. Mater. Chem. A, 2018, 6, 23019–23027 RSC .
10. Y. Jiao, A. M. Hafez, D. Cao, A. Mukhopadhyay, Y. Ma and H. Zhu, Small, 2018, 14, 1800640 CrossRef .
11. J. Wu, F. Ciucci and J. K. Kim, Chem. – Eur. J., 2020, 26, 6296–6319 CrossRef CAS PubMed .
12. J. Theerthagiri, R. A. Senthil, B. Senthilkumar, A. Reddy Polu, J. Madhavan and M. Ashokkumar, J. Solid State Chem., 2017, 252, 43–71 CrossRef CAS .
13. W. He, L. Wang, D. Yin, S. Wang, H. Liu, W. Yu, L. Sun and X. Dong, J. Alloys Compd., 2024, 1007, 176314 CrossRef CAS .
14. Y. Yang, H. Yao, Z. Yu, S. M. Islam, H. He, M. Yuan, Y. Yue, K. Xu, W. Hao, G. Sun, H. Li, S. Ma, P. Zapol and M. G. Kanatzidis, J. Am. Chem. Soc., 2019, 141, 10417–10430 CrossRef CAS PubMed .
15. E. Antolini, Appl. Catal., B, 2016, 181, 298–313 CrossRef CAS .
16. E. Akbari and Z. Buntat, Int. J. Energy Res., 2017, 41, 92–102 CrossRef .
17. Q.-L. Yan, M. Gozin, F.-Q. Zhao, A. Cohen and S.-P. Pang, Nanoscale, 2016, 8, 4799–4851 RSC .
18. Z. Lotfi, M. B. Gholivand and M. Shamsipur, Mater. Today Chem., 2023, 30, 101519 CrossRef CAS .
19. S. A. H. Monfared, H. Beitollahi and M. B. Askari, Diamond Relat. Mater., 2024, 142, 110805 CrossRef CAS .
20. M. Shojaeifar, M. B. Askari, S. R. S. Hashemi and A. Di Bartolomeo, J. Phys. D: Appl. Phys., 2022, 55, 355502 CrossRef CAS .
21. A. VahidMohammadi, J. Rosen and Y. Gogotsi, Science, 2021, 372, 1165 CrossRef PubMed .
22. K. Li, J. Zhao, A. Zhussupbekova, C. E. Shuck, L. Hughes, Y. Dong, S. Barwich, S. Vaesen, I. V. Shvets, M. Möbius, W. Schmitt, Y. Gogotsi and V. Nicolosi, Nat. Commun., 2022, 13, 6884 CrossRef CAS .
23. Y. Guan, S. Zhou, L. Tan, R. Zhao, Q. Zhang, H. Zhu, X. Li, Z. Dong, H. Duan, D. Li, V. Nicolosi, Y. Cong and K. Li, Energy Storage Mater., 2025, 75 DOI:10.1016/j.ensm.2025.104032 .
24. K. Li, X. Wang, S. Li, P. Urbankowski, J. Li, Y. Xu and Y. Gogotsi, Small, 2019, 16, 1906851 CrossRef PubMed .
25. H. Duan, K. Li, M. Xie, J.-M. Chen, H.-G. Zhou, X. Wu, G.-H. Ning, A. I. Cooper and D. Li, J. Am. Chem. Soc., 2021, 143, 19446–19453 CrossRef CAS PubMed .
26. L. Ma, X. Zhou, J. Sun, P. Zhang, B. Hou, S. Zhang, N. Shang, J. Song, H. Ye, H. Shao, Y. Tang and X. Zhao, J. Energy Chem., 2023, 82, 268–276 CrossRef CAS .
27. R. Chen, J. Shen, K. Chen, M. Tang and T. Zeng, Appl. Surf. Sci., 2021, 566, 150651 CrossRef CAS .
28. F. Ozaki, S. Tanaka, Y. Choi, W. Osada, K. Mukai, M. Kawamura, M. Fukuda, M. Horio, T. Koitaya, S. Yamamoto, I. Matsuda, T. Ozaki and J. Yoshinobu, ChemPhysChem, 2023, 24, e202300477 CrossRef CAS PubMed .
29. L. Sha, K. Ye, G. Wang, J. Shao, K. Zhu, K. Cheng, J. Yan, G. Wang and D. Cao, Chem. Eng. J., 2019, 359, 1652–1658 CrossRef CAS .
30. P. Suresh, A. Natarajan and A. Rajaram, Langmuir, 2024, 40, 9509–9519 CrossRef CAS PubMed .
31. A. Yousef, M. H. El-Newehy, S. S. Al-Deyab and N. A. M. Barakat, Arabian J. Chem., 2017, 10, 811–822 CrossRef CAS .
32. C. Yang, W.-Q. Cao, X.-F. Ji, J. Wang, T.-L. Zhong, Y. Wang and Q. Zhang, Renewable Energy, 2020, 146, 699–704 CrossRef CAS .
33. R. Chong, B. Wang, D. Li, Z. Chang and L. Zhang, Sol. Energy Mater. Sol. Cells, 2017, 160, 287–293 CrossRef CAS .
34. Y. J. Tseng and D. Scott, Energies, 2018, 11, 2259 CrossRef .
35. L. Yang, R. He, X. Wang, T. Yang, T. Zhang, Y. Zuo, X. Lu, Z. Liang, J. Li, J. Arbiol, P. R. Martínez-Alanis, X. Qi and A. Cabot, Nano Energy, 2023, 115, 108714 CrossRef CAS .

---

Footnote

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d5nj02200b

This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2025