Non-carbonization annealing toward regulation of cobalt-based organic–inorganic hybrids as advanced electrocatalysts for water splitting

Abstract

High-temperature carbonization typically used in the preparation of advanced electrocatalysts poses significant challenges in preserving abundant functional groups essential for reactant adsorption and component stabilization. To address this, a solvothermal synthesis followed by non-carbonization annealing approach is proposed to fabricate a series of cobalt-based organic–inorganic hybrids derived from cobalt-based glycerate nanospheres (GNs). Notably, annealing in phosphorous and inert atmospheres preserves the solid nanospherical structure, whereas treatment in sulfur-rich environments results in the formation of hollowed nanospheres. Among these hybrids, phosphorized solid cobalt GNs (Co-P-GNs) exhibit the highest catalytic activity for hydrogen evolution reaction (HER), achieving a low overpotential of 152 mV at 10 mA cm−2. Meanwhile, sulfurized hollow cobalt-iron GNs (Co-Fe-S-HGNs) demonstrate good performance in catalyzing oxygen evolution reaction (OER), with a low overpotential of 273 mV at 10 mA cm−2. Both catalysts exhibit robust stability and maintain 100 % Faradaic efficiency during operation in electrolyzers for water splitting. The high performance not only stems from the well-dispersed phosphide and sulfide crystallites, offering ample catalytic active sites; but also benefits from the partially thermolyzed organic matrix enriched with heteroatoms and functional groups, which facilitates ion adsorption to initiate the reactions and tightly clenches loaded components to stabilize the active species.