Boosting oxygen evolution of LiCoO2 electrocatalysts via lithium defect

Abstract

The challenge of the complex oxygen evolution reaction (OER) currently impedes the efficient production of hydrogen via electrolytic water splitting. To address this issue, the development and improvement of effective electrocatalysts are required. LiCoO₂, a key material in lithium-ion batteries, has shown promising potential as an electrocatalyst for electrochemical energy conversion. However, OER catalysts derived from LiCoO₂ have faced obstacles such as high overpotential and a complicated preparation process. In this study, the preparation method is adjusted to optimize the synthesis of Li_1-xCoO₂ with a defective structure, resulting in an impressive overpotential of only 290 mV at a current density of 100 mA cm⁻² and a remarkable Tafel slope of 15.2 mV dec⁻¹. The exceptional catalytic activity of Li_1-xCoO₂ can be attributed to the absence of Li, which triggers oxidative alterations in the electronic structure of Co. Density functional theory (DFT) calculations reveal that Li defects can influence the d-band center of active Co sites, enhancing the adsorption capabilities of Co sites towards *OOH intermediates and increasing the conductivity of the electrocatalyst during the OER process. These alterations improve the velocity of the crucial step in the reaction, ultimately boosting the catalyst's overall performance and efficiency.