Anion switched cobalt-based two-dimensional porous nanosheets for effective alkaline overall water splitting

Modulating the electronic structure of catalysts to optimize the coupling between hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes is an effective strategy to promote the large-scale application of water splitting. Herein, porous Co-based nitrogen oxide two-dimensional nanosheets incorporating Tungsten (W) doping are rationally fabricated to boost alkaline water splitting performance. The highly efficient and readily integrated HER and OER catalysts were successfully synthesized by fine-tuning the ratio of anion oxygen to nitrogen in cobalt-based catalysts through precise control of the nitriding temperature of the precursor. Moreover, W-doping induces effective lattice contraction and electronic structure engineering, facilitating intermediate adsorption/desorption processes and significantly enhancing catalyst kinetics. Therefore, the W-CoN loaded on carbon cloth (W-CoN/CC) porous nanosheets with high N/O ratio, formed through high-temperature calcination, enabling an HER overpotential of merely 41 mV at 10 mA cm^-2. Conversely, the W-CoO/CC two-dimensional porous nanosheets with high O/N ratio prepared by low-temperature calcination exhibited good OER performance, achieving an overpotential of 214 mV at a current density of 10 mA cm^-2. Furthermore, integrating both catalysts enables overall water splitting, and the resulting electrolyzer can be powered by solar panels for efficient hydrogen production.