Interfacial electron redistribution and oxygen vacancy engineering in nanosheet-assembled Co3O4/CuO microspheres toward boosted oxygen evolution reaction.
Abstract
The oxygen evolution reaction (OER) is a key half-reaction in electrochemical water splitting, yet its sluggish four-electron kinetics drives the demand for high-performance, low-cost electrocatalysts. While significant progress has been made in transition metal oxide-based OER catalysts, it remains a major challenge to simultaneously realize morphological optimization for abundant accessible active sites and interfacial electronic modulation to boost intrinsic activity in a single catalyst system. Herein, we report a spray-drying-assisted strategy for the synthesis of hierarchical porous Co3O4/CuO microspheres (HP-CoCu MSs) assembled from wrinkled nanosheets with tunable Cu ratios (x, x = 0.1, 0.2, 0.3, 0.4). The optimized HP-CoCu0.3 MSs deliver a low overpotential of 312 mV at 10 mA cm-2 and a small Tafel slope of 72.4 mV dec-1 in 1.0 M KOH, outperforming pristine hierarchical porous Co3O4 microspheres (HP-Co MSs) and commercial RuO2. The enhanced OER performance is primarily driven by the interfacial electron redistribution at the Co3O4/CuO heterointerface, which optimizes the adsorption energy of oxygenated intermediates and significantly lowers the energy barrier of the rate-determining step. This pivotal electronic effect is coupled with the grain refinement and oxygen vacancies induced by CuO introduction. Meanwhile, the hierarchical porous architecture serves as a structural framework that ensures abundant accessible active sites and rapid mass transport, thereby fully translating these microscopic electronic advantages into macroscopic catalytic performance. This work demonstrates an effective multi-scale engineering strategy for designing advanced non-precious metal OER electrocatalysts through the rational combination of compositional modulation and morphological design.
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