Enhanced electrode stability over engineering Co–B bonds in Co(OH)₂–Ru heterostructure for electrocatalytic water splitting

Strengthening the stability of metal–oxygen (M–O) bonds in catalysts is imperative for the advancement of efficient and durable electrocatalytic water splitting. Herein, using a mild boron-reduction strategy, a self-supported electrode with robust Co–B bonds was constructed. The Co–B@Co(OH)₂–Ru/nickel foam (NF) (Co–B@CRN) electrode demonstrates low overpotentials for alkaline hydrogen evolution reaction (HER, 20 mV) and oxygen evolution reaction (OER, 160 mV) at 10 mA·cm⁻². Furthermore, long-term stability was achieved for over 400 h at 10 mA·cm⁻² and 270 h at 200 mA·cm⁻², respectively. For overall water splitting, the assembled electrolyzer exhibited a low voltage of 1.40 V at 10 mA·cm⁻², with stable operation maintained for over 240 h. Detailed extended X-ray absorption fine structure (EXAFS) characterization verified the mixed valence state of Co and the Co–B coordination environment. Further electronic analysis indicated strong hybridization between Co d-orbitals and B p-orbitals. The B bonding induced a downward shift in the d-band center at the Co site, thereby significantly suppressing metal leaching during catalysis and stabilizing electronic structure regulation. This research shows that the boron reduction strategy offers an effective dynamic regulation mechanism for the electronic structures and coordination environments of transition metals, enabling a highly efficient and stable overall water splitting process.