Aluminum‐Tailored Energy Level and Morphology of Co₃₋<i>_x</i>Al<i>_x</i>O₄ Porous Nanosheets toward Highly Efficient Electrocatalysts for Water Oxidation

Abstract

Tuning energy levels plays a crucial role in developing cost-effective, earth-abundant, and highly active oxygen evolution catalysts. However, to date, little attention has been paid to the effect of using heteroatom-occupied lattice sites on the energy level to engineer electrocatalytic activity. In order to explore heteroatom-engineered energy levels of spinel Co₃ O₄ for highly-effective oxygen electrocatalysts, herein Al atoms are directly introduced into the crystal lattice by occupying the Co²⁺ ions in the tetrahedral sites and Co³⁺ ions in the octahedral sites (denoted as Co²⁺ _Td and Co³⁺ _Oh , respectively). Experimental and theoretical simulations demonstrate that Al³⁺ ions substituting Co²⁺ _Td and Co³⁺ _Oh active sites, especially Al³⁺ ions occupying the Co²⁺ _Td sites, optimizes the adsorption, activation, and desorption features of intermediate species during oxygen evolution reaction (OER) processes. As a result, the optimized Co_1.75 Al_1.25 O₄ nanosheet exhibit unprecedented OER activity with an ultralow overpotential of 248 mV to deliver a current of 10 mA cm^-2 , among the best Co-based OER electrocatalysts. This work should not only provide fundamental understanding of the effect of Al-occupied different Co sites in Co_3-x Al_x O₄ composites on OER performance, but also inspire the design of low-cost, earth-abundant, and high-active electrocatalysts toward water oxidation.