Template Curvature-Induced Tensile Strain Optimizes the Oxygen Evolution Reaction Activity of α-Co(OH)2

Abstract

The high energy barriers of the oxygen evolution reaction (OER) are the main bottleneck in electrocatalytic water splitting, and developing efficient nonprecious metal catalysts is crucial. Here, we report a novel and controllable curvature-induced strain engineering strategy by in situ growing α-Co(OH)₂ (showing potential as an OER catalyst) on SiO₂ nanospheres with different sizes to form a core–shell structure (denoted as PSCo-X). The curvature-induced tensile strain in the α-Co(OH)₂ shell was achieved through the curvature of SiO₂ nanospheres, and the strain magnitude was precisely tuned by adjusting the size of the nanosphere core. Characterization results confirm that the generated tensile strain modulates the electronic structure of α-Co(OH)₂, thereby enhancing the electron-accepting capability of the cobalt centers. Although the introduction of SiO₂ decreases the overall active site density, decreasing the template size and increasing the curvature promote the exposure of active sites. Electrochemical measurements show that PSCo-200 exhibits the optimal OER activity with an overpotential of only 325 mV at 10 mA cm^–2, which is superior to that of pristine α-Co(OH)₂ (360 mV). Furthermore, the C_dl-normalized intrinsic catalytic activity follows the trend of PSCo-200 > PSCo-300 > PSCo-400 > PSCo-100 > pristine α-Co(OH)₂. Additionally, the smaller Tafel slope and lower charge transfer resistance of PSCo-200 facilitate faster reaction kinetics. This work provides an efficient and controllable strategy to enhance the intrinsic activity of α-Co(OH)₂ via curvature-induced strain, offering new insights into the rational design of high-performance OER electrocatalysts.