Effect of molybdenum doping on the catalytic activity of VS2/CNT for the oxygen reduction reaction in alkaline media

Abstract

Development of low-cost catalysts with high catalytic activity is crucial for cathodic reactions (oxygen reduction reaction) of fuel cells. Transition metal dichalcogenides (TMDs) are widely known as energy conversion and storage materials. Although vanadium disulfide (VS₂) is an effective electrocatalyst, especially in hydrogen evolution reactions, it has not been significantly studied for the oxygen reduction reaction (ORR). In this work, vanadium disulfide with different concentrations of molybdenum doping (Mo-VS₂) has been synthesized and the effect of chemical doping on the catalytic activity of VS₂ has been investigated. The structure, morphology, composition, and catalytic activity of the catalyst were detected by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), inductively coupled plasma mass spectrometry (ICP), and electrochemical methods. Finally, the ORR activity of Mo-VS₂ on glassy carbon modified with carbon nanotubes (CNTs) (Mo-VS₂/CNT/GCE) has been studied. The presence of CNTs in the final composite increases the current density and electrocatalytic activity due to good electron conductivity and high specific surface area. The results show that Mo-VS₂/CNT/GCE has significant current density and also has an onset potential of 0.98 V (vs. RHE). The onset potential and half-wave potential of this catalyst have been shifted to more positive potential compared to pure VS₂/GCE, and are important parameters for the catalytic activity of catalysts. The performance of the catalyst is very close to that of the commercial 10% Pt/C catalyst. Furthermore, the Mo-VS₂/CNT/GCE showed maximum power density of 1.13 mW cm⁻² which is near to that for 10% Pt/C (1.53 mW cm⁻²). The results show that the proposed catalyst is a promising candidate for the replacement of platinum in the cathodes of fuel cells.