Chlorine-facilitated amorphous Co-based catalyst with self-termination of surface reconstruction for seawater splitting

Abstract

A highly selective and durable electrocatalyst for the oxygen evolution reaction (OER) is essential for effective seawater splitting, as the side reactions induced by Cl^– ions pose a significant challenge. Employing OER catalysts with excellent crystallinity allows for a thorough investigation of the dynamic restructuring in active sites. Nevertheless, the specific mechanism of reconstruction triggered by the amorphous phase remains unclear. Herein, we integrate simultaneously amorphous structures and lattice chlorine components into Co-based electrocatalysts (Cl-Co/CoO_x-p@GF), enabling us to investigate how lattice chlorine affects the reconstruction mechanism of a highly amorphous structure. Combining in-situ and ex-situ characterizations, we find that the amorphous cobalt oxides undergo re-crystallization, resulting in irreversible surface reconstruction with a terminal layer due to structural flexibility during seawater splitting. Notably, the introduced lattice chlorine acts as a structural buffer, whose sustained leaching during OER can create vacancies for seawater Cl⁻ invasion, thereby preventing catalyst deactivation. Additionally, depending on the photosensitivity of porphyrin-based structural carriers, the Cl-Co/CoO_x-p@GF demonstrates an overpotential of 385 mV vs. RHE at 100 mA cm^–2 while maintaining a current density of 95.4 % over 48 h with the assistance of visible light in alkaline simulated seawater.