Facile Sulfur Doping Control in the Novel Synthesis of Iron Phosphide Nanofilm: A pH-Universal Electrocatalyst for Efficient Hydrogen Evolution

Nonmetal element doping, capable of tuning the electronic structure, active sites, and phase, emerges as a promising modification strategy to develop highly active electrocatalysts. However, managing nonmetal doping levels is significantly more difficult than regulating cation-doping concentration due to the generally complex synthesis process of nonmetal-doped electrocatalysts. The systematic study of how nonmetal doping amount impacts electrocatalytic performances is still largely uncharted. Herein, we have crafted an innovative and scalable method for synthesizing S-incorporated FeP nanofilm electrocatalysts coated on commercial carbon fiber cloth (FeP|S@CFC), featuring a tunable S doping amount. Therefore, the important influence of regularity of sulfur doping concentration on the activity of FeP electrocatalysts is investigated thoroughly for the first time. The obtained FeP|S@CFC with optimized sulfur doping content not only shows excellent catalytic hydrogen evolution reaction performances with an overpotential of only 83 mV at 10 mA cm^–2 and a sufficient durability in the acidic electrolyte but also exhibits dramatically catalytic activities even superior to that of benchmark Pt in neutral and alkaline media. Density functional theory calculations elucidate the mechanism of S-doping concentration modulating the hydrogen evolution activity of FeP|S@CFC. This study provides critical insights into the mechanisms of nonmetallic element doping for boosting electrocatalyst activity. It also opens up new possibilities with regard to efficiently fabricating inexpensive nonmetal-incorporated electrocatalysts with a controllable doping amount for large-scale water electrolysis.