Low Loading of Rh_xP and RuP on N, P Codoped Carbon as Two Trifunctional Electrocatalysts for the Oxygen and Hydrogen Electrode Reactions

摘要

Reducing the consumption of noble metals in energy devices, such as fuel cells, zinc-air batteries, and water splitting cells, is a core issue for achieving an environmentally sustainable society. Herein, two highly efficient electrocatalysts are synthesized, composed of N, P codoped carbon (NPC) modified with noble metals phosphides (RhxP/NPC and RuP/NPC) through pyrolysis of a mixture of RhCl(3)xH(2)O or RuCl3 xH(2)O, respectively, with phytic acid. Unlike the reported rhodium and ruthenium phosphides, RhxP/NPC and RuP/NPC have a low loading of Rh (approximate to 0.4 wt) and Ru (approximate to 0.5 wt) and yet still exhibit excellent trifunctional activities for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. For hydrogen evolution, RhxP/NPC shows a Pt-like activity and excellent durability in acidic medium. Notably, RuP/NPC becomes more active after 2000 cycles in the durability test. For oxygen reduction, both of the catalysts show a half-wave potential of 0.89 V, which is positively shifted 40 mV relative to that of Pt/C (0.85 V) in 0.1 m KOH. In addition, RhxP/NPC and RuP/NPC also exhibit activities superior to that of IrO2 in oxygen evolution. Finally, zinc-air batteries and water splitting cells assembled with RhxP/NPC and RuP/NPC catalysts display good performance.