High-efficient Cr/NiMoB spherical cluster electrocatalyst with superior stability at high current density operation for overall water splitting application at industrial-level conditions

Designing highly efficient electrocatalysts with high current density (HCD) operation capability to generate ultrafine green hydrogen through electrochemical water-splitting at an affordable cost is a considerably challenging task. Herein, Cr-doped NiMoB spherical cluster (SC) is fabricated by a hydrothermal doping approach followed by post-annealing treatment. The Cr/NiMoB SC exhibits remarkably improved alkaline hydrogen and oxygen evolution reaction activities of 195 and 386 mV at 300 mA/cm2, comparable with the state-of-the-art electrocatalysts. The bi-functional system shows an exceptionally low cell voltage of 2.82 V at HCD of 2000 mA/cm2, largely surpassing the benchmarks of Pt/C and RuO2. It also demonstrates outstanding stability for the continuous 120-h at 1000 mA/cm2, satisfying the industrial water-splitting conditions. Further, an ultra-low 2-E cell voltage of 2.49 V under HCD in 6 M KOH is demonstrated by the hybrid configuration of Pt/C(- ) || Cr/NiMoB(+). The synergistic integration of Cr on NiMoB SC optimizes absorption/desorption of reaction intermediates (*H, *OH and *OOH) for high-speed charge transfer and catalytic splitting process. Cr doping can induce new active centers, enlarged electrochemical surface area (ECSA) and enhanced conductivity on top of the catalytic advantages of Ni, Mo and B. Additionally, dual-step thermal annealing can improve the overall crystallinity electrocatalyst.