Hydrogel-Derived Honeycomb Ni3 S4 /N,P-C as an Efficient Oxygen Evolution Catalyst.

The development of high-efficiency electrocatalysts with low costs for the oxygen evolution reaction (OER) is essential, but remains challenging. Herein, a new synthetic process is proposed to prepare Ni3 S4 particles embedded in N,P-codoped honeycomb porous carbon aerogels (Ni3 S4 /N,P-HPC) through a hydrogel approach. The preparation of Ni3 S4 /N,P-HPC begins with the sol-gel polymerization of tripolyphosphate, chitosan, and guanidine polymer that contains metal-binding sites, allowing for the uniform incorporation of Ni ions into the gel matrix, freeze-drying, and subsequent carbonization under an inert atmosphere. This synthesis resolves difficulties in synthesizing the pure Ni3 S4 phase caused by the instability of Ni3 S4 at high temperature, while affording good control of the porous structure and N,P-doping of carbon aerogels. The synergy between the structural advantages of N,P-carbon aerogels (such as easily accessible active sites, high specific surface area, and excellent electron transport) and the intrinsic electrochemical properties of Ni3 S4 result in the outstanding OER performance of Ni3 S4 /N,P-HPC, with overpotentials as low as 0.37 V at 10 mA cm-2 . The work outlined herein offers a simple and effective method for the development of carbon-based electrocatalysts for renewable energy conversion.