Structure-charge transfer-performance relationship of hierarchical NiCo2O4/carbon nanosheets composites for alkaline oxygen evolution

Hierarchical NiCo 2 O 4 /carbon nanosheets composites were constructed through a template-assisted hydrothermal-calcination strategy. • The carbon nanosheets network improves the charge transfer behavior and enhances the intrinsic active site. • The optimized NiCo 2 O 4 /CNs-2 electrode delivers 285 mV at 10 mA cm −2 with a Tafel slope of 58.2 mV dec −1 for alkaline OER. The oxygen evolution reaction (OER) poses a key kinetic bottleneck for electrochemical water splitting due to its sluggish four-electron transfer kinetics. Spinel NiCo 2 O 4 is a promising non-precious candidate, while its practical application is constrained by poor electrical conductivity, limited stability and insufficient intrinsic activity. Herein, we report a hierarchical composite (NiCo 2 O 4 /CNs), in which NiCo 2 O 4 nanosheets are uniformly anchored onto three-dimensional carbon nanosheets network via a template-assisted hydrothermal strategy. The introduction of CNs simultaneously enables asymmetric Ni 2+ /Ni 3+ and Co 2+ /Co 3+ valence ratio via strong interfacial coupling and ensures rapid electron transfer via the interconnected conductive network. As a result, the optimized NiCo 2 O 4 /CNs-2 composite exhibits enhanced OER performance in alkaline media, with an overpotential of only 285 mV to achieve 10 mA cm −2 and a Tafel slope of 58.2 mV dec −1 . pH-dependence analysis reveals a higher proton reaction order (0.894) than pristine NiCo 2 O 4 (0.641), suggesting an enhanced lattice oxygen involved contribution, which is corroborated by post-OER XPS, Raman, and XRD analyses confirming LOM-triggered surface reconstruction into Ni x Co 1-x (OH) 2 active phase. This work highlights a novel 2D/3D composite strategy that regulates the Charge-transfer behavior of metal oxides through morphological modulation of carbon supports, offering a promising route toward high-performance, durable non-precious metal electrocatalysts for practical water splitting applications.