High-performance Mo2C/MWCNT electrocatalyst for MOR: Comparison with MoO2/MWCNT and MoO3/MWCNT

• Published in: International journal of hydrogen energy 2023-10, Vol.48 (83), p.32408-32419
• Main Authors: Gao, Xue-Ting, Wang, Yi-Fan, Fu, Lin, Zhang, Rui-Xin, Li, Rui-Min, Gao, Zhi-Hua, Yan, Zhi-Feng, Liu, Yi-Ming, Huang, Wei, Liu, Lei, Zuo, Zhi-Jun
• Format: Article
• Language: English
• Subjects: Direct methanol fuel cell; Methanol oxidation reaction; Mo2C; MWCNT
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.05.009

Methanol oxidation reaction (MOR) in the direct methanol fuel cells involves six electron transfer processes, and noble metal based catalysts such as Pt and Pd are still recognized as efficient catalysts for MOR. It is generally accepted that the reaction is mainly related to the d states of precious metal-based catalysts. Transition metal carbides and noble metals exhibit similar d band structure and catalytic properties, among which molybdenum carbide is an effective catalyst. However, molybdenum carbide-based catalysts have not been used in methanol electrooxidation reactions until the present moment, and we tried to use Mo2C/MWCNT for the MOR reaction. Compared with MoO2/MWCNT and MoO3/MWCNT, it is found that Mo2C/MWCNT shows the highest electrocatalytic activity, and the current density of Mo2C/MWCNT is 185 mA cm−2 in 1 M KOH+1 M CH3OH at 0.70 V (vs. Hg/HgO). The current density is about 2.2 times and 1.4 times higher than those of MoO2/MWCNT and MoO3/MWCNT catalysts, respectively, and the electrochemical impedance also decreases markedly. The current density retains 76.19% of the initial catalytic activity after 10 h at the Mo2C/MWCNT electrode, indicating that the catalyst has superior stability for MOR. The reaction pathway of MOR on Mo2C/MWCNT is as follows: CH3OH∗ → CH3O∗→ CH2O∗ → CH2OOH∗ → CH2OO∗ → CHOO∗ → CO2∗. The result not only expands the Mo2C application area, but also provides a new idea for the design of the MOR catalyst. [Display omitted] •The current density of Mo2C/MWCNT is 185 mA cm−2 at 0.70 V (vs. Hg/HgO).•Mo2C/MWCNT also shows high electrocatalytic stability.•Mo 4d orbit of Mo2C/MWCNT is similar to the d-band structure of precious metals.•The charge transfers from Mo2C to MWCNT.