Effect of transition metals (Ni and Co) in the methanol oxidation reaction electrocatalytic activity on Mo2C/MWCNT

Abstract

The direct methanol fuel cells still recognize Pt and Pd as efficient catalysts for the methanol oxidation reaction (MOR). Our previous study demonstrated the high activity and stability of the Mo2C/MWCNT catalyst for electrocatalytic MOR. To further enhance the performance of Mo2C/MWCNT, the second metals (Ni and Co) are introduced onto Mo2C/MWCNT. It is found that Ni-Mo2C/MWCNT exhibits the highest electrocatalytic MOR activity, with a current density of 192 mA cm−2 in 1 mol/L(M) KOH + 1 M CH3OH electrolyte at 0.6 V (vs. Hg/HgO). Additionally, the stability of Mo2C/MWCNT significantly improves after Ni doping (85.61 % vs. 76.19 %). Characterization results reveal a strong interaction between Ni species and Mo2C, with some Ni ions doping into Mo2C. Furthermore, the Ni-Mo2C nanoparticles are evenly dispersed on MWCNT, with nanoparticle sizes ranging from 5 to 10 nm. DFT results indicate a charge transfer from Mo2C to Ni, resulting in the shift of the d-band center of the surface away from the Fermi level. Moreover, the interface charge transfer resistances of Ni- Mo2C/MWCNT significantly decreased (7.2 vs. 20.0 Ω). As a result, the electrocatalytic MOR activity on Ni- Mo2C/MWCNT improved compared to Mo2C/MWCNT.