Tailoring a local acidic microenvironment on amorphous NiMoB catalyst to boost alkaline and neutral hydrogen evolution reactions

Improving hydrogen evolution reaction (HER) kinetics in alkaline and neutral environments is crucial for reducing energy consumption in industrial electrolyzers. Here, we propose a strategy to tailor the chemical reaction microenvironment through crystal phase engineering and electronic structure modulation. Taking amorphous Am-NiMoB as a case study, we successfully created a local acid-like microenvironment in both alkaline and neutral media, enabling superior HER performance. Operando Raman spectroscopy confirmed the in-situ generation of abundant hydronium ions (H₃O⁺) intermediates on the Am-NiMoB surface during HER. Electrochemical analysis and theoretical calculations reveal that the enriched oxygen vacancies in Am-NiMoB facilitate H₂O dissociation, while Mo doping reduces the binding strength of H* intermediates. These factors are key contributors to the formation of this unique acidic surface. Am-NiMoB exhibits high performance typically associated with acidic environments, with overpotentials of 38 and 48 mV to achieve a current density of 10 mA cm⁻² and Tafel slopes of 34.4 and 39.4 mV dec⁻¹ in alkaline and neutral electrolytes, respectively. Notably, Am-NiMoB demonstrates robust durability for over 350 h during seawater electrolysis at 500 and 1000 mA cm⁻². This work exemplifies the potential of enhancing catalytic activity through interfacial microenvironment modulation.