▎ 摘　　要

Development of efficient and stable electrodes for hydrogen and oxygen evolution from water constituted of abundant elements and prepared by sustainable and scalable procedures is of considerable importance for producing green hydrogen from renewable electricity. Herein, a method for the preparation of Ni2P, Fe2P, and FeP supported on N-doped graphene (NiP/NG and FeP/NG) is reported. The procedure uses metal salts, phosphorous oxide, and chitosan as precursors of metal phosphide and N-doped graphene, avoiding the use of undesirable and hazardous precursors, such as PH3 or NaH2PO2, and rendering a material with a strong metal phosphide-graphene interaction. Moreover, NiP/NG and FeP/NG electrodes are demonstrated to be more efficient than the benchmark catalysts Pt/C and RuO2, for hydrogen evolution reaction and oxygen evolution reaction, respectively, at a large current density (300 mA/cm(2)). In addition, water electrolysis was carried out using NiP/NG//FeP/NG electrodes, also demonstrating improved efficiency and stability compared with Pt/C//RuO2 at a current density (400 mA/cm(2)) near industrial requirements.