Self-protecting MnMoO4@CoS2/MoS2/CC composite heterojunction catalysts for stabilizing hydrogen evolution in alkaline solutions

Transition metal disulfide compounds (TMDs) catalysts exhibit excellent catalytic ability in hydrogen evolution reaction (HER), but they are susceptible to OH- poisoning under strong alkali conditions leading to active site inactivation, thus affecting their catalytic activity and stability. In this regard, we propose a catalyst “self-protection” strategy against OH - attack. Specifically, we synthesized a composite heterojunction MnMoO 4 @CoS 2 /MoS 2 on carbon cloth (CC) by a hydrothermal and calcination process. The experimental results show that MnMoO 4 undergoes reconfiguration during the HER process, and its MoO 4 2- takes the lead in dissolving in the electrolyte before being re-adsorbed on the surface of the electrocatalyst to form a protective layer, which greatly inhibits the erosion of OH - on the catalyst and effectively prevents the oxidation of the Mo 4+ and the edge S sites, which is beneficial to the long-term stability of the catalyst. The CoS 2 /MoS 2 heterojunction provides more active sites and higher conductivity to enhance its catalytic activity. The products exhibit overpotentials of only 71 and 171 mV at current densities of 10 and 100 mA cm −2 , and have long-term stability of over 100 h. In comparison, the samples after base hydrolysis treatment (deprotection) showed a significant performance decay. This study provides a novel approach for the rational design of efficient and stable TMDs catalysts.