Boride-derived catalysts for hydrogen evolution: Precursor-controlled reconstruction toward M-Co(OH)2 and M-Ni(OH)2 active phases and their application in Al-H2O batteries

Transition-metal borides have long been developed as promising electrocatalysts for the hydrogen evolution reaction (HER); however, the identity of their true active phase remains controversial. Here, in conjunction with our previous studies, by systematically investigating a series of cobalt- and nickel-boride-derived catalysts through a combined computational and experimental screening, we reveal that HER activity universally originates from the synergistic interaction between metallic sites and hydroxide matrices, enabled by lattice expansion, interfacial electronic transfer, and dynamic surface evolution. As a representative high-performance example, Pt-modified Co(OH) 2 derived from cobalt boride exhibits ultralow overpotentials of 11 mV at 10 mA cm −2 and 95 mV at 500 mA cm −2 , together with long-term stability. Importantly, the same reconstruction principle applies to Ni-boride systems, confirming the generality of this approach. Beyond water electrolysis, we further demonstrate that these HER catalysts are highly effective in Al-H 2 O batteries, where hydrogen evolution is coupled with electrical energy harvest. An alkaline Al-H 2 O battery employing the reconstructed catalyst delivers a power density of 21.96 mW cm −2 . This work establishes that the activity of “boride-based” HER catalysts fundamentally arises from reconstructed metal-hydroxide active centers, providing a development paradigm of transition-metal electrocatalysts.