Negative Electrocatalytic Effects of p-Doping Niobium and Tantalum on MoS₂ and WS₂ for the Hydrogen Evolution Reaction and Oxygen Reduction Reaction

Transition-metal dichalcogenides (TMDs) are at the forefront of research for their promising catalytic abilities and unique materials properties. With great interest in the study of mono- or few-layered TMDs, we seek to fundamentally explore the effects of doping on bulk TMDs, particularly MoS₂ and WS₂ for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) with p-dopants Nb and Ta. Despite promises reported in the computational studies of doped TMDs on the HER, our results show otherwise. Doped bulk TMDs display less catalytic activity in comparison to their undoped counterparts for the HER. A similar effect is observed for ORR catalysis. Characterization was done to shed light on its surface elemental composition, properties, and morphologies. It was found that doped WS₂ has a high percentage of 1T phase but this does not correlate with a lower overpotential for the HER at -10 mA cm^-2, which contradicts the general consensus. We therefore show that p-dopants have a negative electrocatalytic effect on the HER. These findings are of high importance for the field of TMD electrochemistry, as they challenge the current consensus that doping always improves the electrocatalysis of TMDs.