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 FeNi₃-550/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 FeNi₃-550/C demonstrate considerable overpotential for hydrogen evolution reaction (59.5, 74.5 and 94.5 mV at - 10 mA cm^-2) and oxygen evolution reaction (312.5, 365.5 and 333.5 mV at 10 mA cm^-2) in an alkaline electrolyte and overpotentials for hydrogen evolution reaction (66.5, 81.5 and 106.5 mV at - 10 mA cm^-2) 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 FeNi₃-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^-2. 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.