Regulation of the electronic structure of Co4N with novel Nb to form hierarchical porous nanosheets for electrocatalytic overall water splitting

Abstract Heretofore, the metal elements constituting the electrolyzed water catalysts are almost all Fe, Co, and Ni, and the accelerator elements are V, W, Ce, etc., but there is a lack of exploration for other elements. Niobium (Nb) is a promising promoter due to its complex chemical properties and the ability to react with many elements to form abundant compounds. Taking Co4N as the research case, this work incorporates Nb atoms to tune the d orbital of metallic Co4N nanowires. Experimental results and density functional theory calculations show that due to the adjustment of Nb atoms, the d-band center of Co4N moves down, which helps facilitate the desorption of H2. At the same time, abundant Co3+ active sites are generated on the surface of Nb–Co4N, which is crucial for the formation of oxygen evolution reaction (OER) intermediates (∗OOH). Nb-regulated Co4N nanosheets on the three-dimensional Ni foam (Nb–Co4N/NF) drives the current density of 20 mA cm−2 at a low overpotential of 90 mV for hydrogen evolution reaction and 273 mV for OER, respectively. This work inspires a novel idea for the rational design and synthesis of highly efficient electrocatalysts composed of novel less used elements for overall water splitting.