Liquid nitrogen quenching for efficient Bifunctional electrocatalysts in water Splitting: Achieving four key objectives in one step.

Herein, a novel liquid nitrogen quenching treatment is proposed to achieve multifaceted modulation involving morphological modulation, lattice tensile strain modulation, metal active centre coordination reconstruction and grain boundary construction within a series of intermetallic compounds modified on a carbon substrate (CoFe-550/C, CoNi-550/C and FeNi-550/C, where 550 refers to liquid nitrogen quenching temperature and C refers to the carbon substrate). Noteworthily, the optimising intermediate absorption/desorption process is achieved by multifaceted modulation. Consequently, CoFe-550/C, CoNi-550/C and FeNi-550/C demonstrate considerable overpotential for hydrogen evolution reaction (59.5, 74.5 and 94.5 mV at - 10 mA cm) and oxygen evolution reaction (312.5, 365.5 and 333.5 mV at 10 mA cm) in an alkaline electrolyte and overpotentials for hydrogen evolution reaction (66.5, 81.5 and 106.5 mV at - 10 mA cm) in simulated seawater with 1.0 M KOH + 0.5 M NaCl (89.5, 97.5 and 115.5 mV in 0.5 M NaCl), respectively. In addition, the CoFe-, CoNi- and FeNi-based electrolysers exhibit prominent overall water-splitting activity in an alkaline environment (1.59, 1.77 and 1.69 V, respectively) at 10 mA cm. Overall, the proposed liquid nitrogen quenching strategy opens up new possibilities for obtaining highly active electrocatalysts for the new generation of green energy conversion systems.