Transition Metal Co-Induced Phase Transition of CoxMo1–xSe2 to Promote a Hydrogen Evolution Reaction

MoSe2 has been used as a promising alternative strategy to noble metal catalysts in hydrogen evolution reactions (HER). Based on the electronic structure and phase transition of the transition metal Co-induced 2H MoSe2, CoxMo1–xSe2 (x = 0–1) was synthesized using a one-step hydrothermal method. With increasing Co doping, the HER performance of CoxMo1–xSe2 shows an increasing and then decreasing trend in alkaline electrolytes, where Co0.6Mo0.4Se2 exhibits the strongest HER activity, which is supported by the predicted results of the Gibbs free energy and water dissociation energy. Structural characterization and first-principles calculations consistently show a 2H→1T phase transition of MoSe2 in CoxMo1–xSe2 at x = 0.4–0.8. The increase in electron density near the Fermi level and the change in the band gap with increasing Co doping confirm that the doping of the Co causes CoxMo1–xSe2 to exhibit pronounced metallicity. The maximum electronic contribution to the partial density of states of Mo atoms at x = 0.67 and a band gap of 0 allow Co0.6Mo0.4Se2 to exhibit a very low charge transfer resistance and a good Tafel slope. This study provides inspiration and plays an important role in the design of TMD-based HER catalysts with high catalytic activity.