Ultrapure Molybdenum Disulfide Shows Enhanced Catalysis for Hydrogen Evolution over Impurities-Doped Counterpart

The development of electrocatalysts to meet the requirements of renewable energy applications has seen much attention placed on transition-metal dichalcogenide (TMD) materials owing to their promising properties. In particular, the strategy of atomic doping has garnered some success in tuning the electronic properties and harnessing the vast potential that TMDs can offer in the catalysis of the hydrogen evolution reaction (HER). Moreover, with computational studies reporting the promising effects of transition-metal doping, such a strategy has been adopted with much enthusiasm. Herein, we consider one of the most prevalent TMDs, that is, MoS₂, and the possible presence of impurities arising from its preparation method and starting materials that may act as dopants to affect its electronic and catalytic properties. An ultrapure MoS₂ material was synthesized and compared with a relatively impure MoS₂ sample obtained commercially. Ultrapure MoS₂ was found to outperform its impurities-doped counterpart in HER catalysis. These findings not only provide valuable insight into the influence of parts-per-million concentrations of impurities on the catalytic activity of TMD materials but also highlight the importance of the intentional and proper design of atomic doping to realize its true effects. At the same time, the need for a more in-depth understanding and evaluation of the benefits of the atomic-doping strategy in the experimental setting as a means to harness the potential of TMDs as catalysts for hydrogen evolution is also revealed.