Kinetically accelerated oxygen evolution reaction in metallic (oxy)hydroxides enabled by Cr-dopant and heterostructure

Efficient water-splitting is an underpinning technology for producing hydrogen in high-purity and enabling hydrogen economy, but it suffers from the sluggish kinetics of anodic oxygen evolution reaction (OER). Cost-efficient transition metals-based oxides/hydroxides, particularly NiFe-based double hydroxides (NiFe LDHs), have been deemed as promising OER electrocatalysts in alkaline electrolytes. However, their electrocatalytic performance still waits to be substantially optimized. Herein, we demonstrate the tremendously enhanced OER activity of NiFe LDH via a developed coupling strategies of intrinsic chromium (Cr) doping and external heterojunction engineering. Relying on the heterostructure, an in-built electric field is proved and thus the charge transfer kinetic is substantially accelerated. Remarkably, the synergistic surface electron modulation, explicitly revealed by theoretical calculation and experimental analysis, elucidates that the upward d-band center of Fe sites after doping Cr accounts for the much-enhanced OER activity, being inherited when combining with CuO substrate, while the increased empty d orbital of Ni sites after introducing CuO part interprets the activation of initially nonactive Ni sites. As a result, a low OER overpotential of 210 mV (at 10 mA cm−2) and excellent durability are achieved for Cr-NiFe LDH@CuO catalyst. Furthermore, the resultant alkaline electrolyzer also displays outstanding activity (requires a low voltage of 1.56 V at 100 mA cm−2) and good durability.