One-Step Electrodeposition Synthesized High Performance Quarternary Ni-Co-S-P for Efficient Water-Splitting

Abstract

Environmental problems are getting worse and there is a growing demand for developing clean energy to replace decreasing fossil fuels. Hydrogen is one of the most promising alternatives to fossil energy. Electrochemical water splitting is a simple, efficient and environmentally friendly technology of hydrogen production. It has attracted more attention and research because it can transform electrical energy into chemical energy, which is more convenient for transportation and storage. However, overpotential often exists in practical application due to the influence of uphill reaction. The use of electrocatalysts can reduce the overpotential. For decades, people have made great efforts in lowering the driving overpotential and improving catalytic activity of low-cost electrocatalysts. There is a need for synergy in the following aspects: 1. Increasing the intrinsic activity and density of the catalytic sites. Optimizing the adsorption Gibbs free energy of reaction adsorption and constructing low dimensional morphology to increase the specific surface area of the catalysts. 2. Increase the carrier concentration and diffusion rate by combining with carbon materials or by doping impurities into intrinsic semiconductors. 3. Multicomponent synergism. For example, in nickel-cobalt alloyed, Ni sites is more favorable to desorption of hydroxide in alkaline condition, thus improving TOFs of catalyst. Meanwhile, Co sites offer a faster kinetics the Heyrovsky and Tafel steps, which is more favorable to the rapid detach of as-generated hydrogen. 4. Improving mass transfer performance is helpful to the rapid detachment of generating bubbles and the acceleration of water splitting. Transition metal phosphides (TMPs) have been extensively studied in the past decade because phosphide-based materials have faster kinetics than common oxides, sulfides, and hydroxides. Meanwhile, transition metal sulfides (TMSs), with relatively lower intrinsic electrical resistivity, which could facilitate charge transfer during the electrocatalytic HER/OER process, have attracted considerable interest. Based on the above design principles, we prepared a superaerophobic Ni-Co-S-P by one-step electrodeposition. The obtained catalysts have extremely low overpotential and favorable kinetic properties. This study provides a new approach for the development of non-noble metals catalyst toward electrochemical water splitting.