Cathodic NiOOH emerging during hydrogen release toward a strong coupling catalyst for durable ampere-level H2 generation

Abstract

Elaborate interface engineering based on in situ surface reconstruction during catalysis, especially at the cathode, is effective at promoting the hydrogen evolution reaction (HER) but is plagued by the uncontrollable extent of the reconstruction and structure collapse. In view of the reasonable adsorption of reaction intermediates and accelerating kinetics of hydroxy oxides (MOOH), we focused on the in situ structural evolution of the HER electrode toward MOOH during catalysis, which has been revealed by operando Raman spectroscopy yet seldom reported. As a typical example, Mn-doped NiS₂ was selected as the HER electrode to monitor in situ structural evolution toward hydroxy oxides (cathode in situ-derived NiOOH, CISD-NiOOH) as Mn-NiS₂@CISD-NiOOH coupling catalysts. In situ formation of MOOH on the cathode is interesting. Moreover, the existence of Mn dopants renders Mn-NiS₂ with lattice distortion and a rough surface consisting of nanoparticles of ∼25 nm in diameter, differing from the smooth NiS₂. In 1 M KOH, Mn-NiS₂@CISD-NiOOH exhibits a low overpotential of 330 mV to deliver 1000 mA cm⁻² and an excellent stability of 100 h at 1300 mA cm⁻². Notably, in alkaline seawater (1 M KOH + seawater) as well as 30% KOH industrial electrolyte, it still exhibits stable HER operation above 1000 mA cm⁻² for at least 100 h. This study not only expands the prospects for in situ cathode structure development but also offers a robust catalytic cathode with high activity for industrial hydrogen-production systems.