Ni-regulated electronic structure and interfacial kinetics in CoCr multi-component alloys enable efficient and...

The intrinsic electrocatalytic activity of catalysts is strongly correlated with their electronic structure, surface coordination environment, and density of active sites. Multi-component alloys possess tunable chemical compositions and distinctive structural features, which provide abundant regulatory avenues for optimizing catalytic performance. Herein, ternary CoCr multi-component alloys with varied Ni contents, denoted as Ni _x (CoCr)_100-x (x = 30, 40, 50, 60), were fabricated as research objects to systematically investigate how Ni fraction modulates microstructural evolution and electrocatalytic behaviors toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Comprehensive electrocatalytic evaluations were implemented in both alkaline freshwater and alkaline seawater electrolytes. In 1.0 M KOH alkaline freshwater, the Ni₅₀(CoCr) alloy delivers overpotentials of 120 mV for HER and 276.6 mV for OER at a current density of -10 mA cm^-2 and 10 mA cm^-2, respectively. To unravel the interfacial reaction kinetics between the electrode and electrolyte, multi-potential Bode plots and Distribution of Relaxation Times (DRT) analyses were adopted. The Bode phase angle declines with elevated applied potential, indicating a continuous reduction in charge transfer resistance. Meanwhile, DRT spectra exhibit only one dominant characteristic peak whose intensity monotonically decreases with increasing overpotential, unambiguously verifying that the interfacial electrocatalysis is governed solely by the charge-transfer step. Considering the abundant, easily accessible reserves of seawater, it serves as an ideal electrolyte for large-scale electrochemical energy conversion and is more consistent with industrial application scenarios compared to pure freshwater. When tested in 1.0 M KOH + seawater mixed electrolyte, the Ni₅₀(CoCr) alloy achieves HER and OER overpotentials of 217.3 mV and 314.3 mV at -10 mA cm^-2 and 10 mA cm^-2, respectively. Moreover, this alloy maintains stable electrocatalytic performance over a continuous 100 h chronoamperometric test in both alkaline freshwater and alkaline seawater media, demonstrating outstanding long-term durability. This work offers reliable experimental evidence and theoretical guidance for developing low-cost, high-performance, long-lived non-noble electrocatalysts targeted at direct seawater electrolysis, and facilitates the large-scale and sustainable advancement of green hydrogen energy technologies.