Efficient electrocatalysts for OER: Amorphous cerium-doped cobalt sulfide with enhanced performance and durability

Developing highly efficient electrocatalysts is essential for advancing the oxygen evolution reaction (OER), a key step in water splitting. In this study, a novel approach for the synthesis of an amorphous sulfide structure has been presented. First, a cerium-doped zeolitic imidazolate framework-67 (Ce-ZIF-67) using a co-precipitation method, followed by a multi-step transformation process. This process includes oxidation to form cerium-doped cobalt oxide (Ce-CO) and a subsequent sulfidation step to produce an amorphous cerium-doped cobalt sulfide (Ce-CS) structure. The introduction of cerium and the formation of an amorphous sulfide structure result in a significantly enhanced OER performance due to increased atomic disorder, improved electron mobility, and an expanded active surface area. Remarkably, the Ce-CS structure achieved a reduction in overpotential from 352 mV for Ce-CO to 291 mV at 100 mA cm⁻² in 1.0 M KOH, alongside a Tafel slope reduction from 86.2 mA decade⁻¹ to 67.2 mV decade⁻¹. These enhancements underline the importance of cerium doping and amorphization in optimizing electrocatalytic efficiency. Furthermore, the Ce-CS catalyst demonstrated exceptional durability, with no observable degradation in performance or structural integrity after 10 h of continuous operation. This work presents a pioneering strategy for designing and synthesizing highly effective OER electrocatalysts, contributing a significant advancement to the field.