Molten-Salt Electrochemical Preparation of Co₂B/MoB₂ Heterostructured Nanoclusters for Boosted pH-Universal Hydrogen...

Boosting the hydrogen evolution reaction (HER) activity of α-MoB₂ at large current densities and in pH-universal medium is significant for efficient hydrogen production. In this work, Co₂B/MoB₂ heterostructured nanoclusters are prepared by molten-salt electrolysis (MSE) and then used as a HER catalyst. The composition, structure, and morphology of Co₂B/MoB₂ can be modulated by altering the stoichiometries of raw materials and synthesis temperatures. Impressively, the obtained Co₂B/MoB₂ at optimized conditions exhibits a low overpotential of 297 and 304 mV at 500 mA cm^-2 in 0.5 m H₂SO₄ and 1 m KOH, respectively. Moreover, the Co₂B/MoB₂ catalyst possesses a long-term catalytic stability of over 190 h in both acidic and alkaline medium. The excellent HER performance is due to the modified electronic structure at the Co₂B/MoB₂ heterointerface where electrons are accumulated at the Mo sites to strengthen the H adsorption. Density functional theory (DFT) calculations reveal that the formation of the Co₂B/MoB₂ heterointerface decreases the H adsorption and H₂O dissociation free energies, contributing to the boosted HER intrinsic catalytic activity of Co₂B/MoB₂. Overall, this work provides an experimental and theoretical paradigm for the design of efficient pH-universal boride heterostructure electrocatalysts.