Electroplating multicomponent transition-metal phosphide nanoparticles on hydrophobic graphene aerogels for electrocatalytic green ammonia synthesis

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) for ammonia synthesis powered by renewable electricity under ambient conditions is an energy efficient, green, and environmentally friendly synthesis route, in comparison with the industrial HaberBosch process. However, NRR suffers from insufficient NH3 yield and low Faraday efficiency (FE), and the search for suitable NRR catalysts is of great importance. In this work, CoNiFeP nanoparticles were loaded on graphene aerogel (x-CNFP@GA-y) by electroplating, successfully synthesizing x-CNFP@GA-y monolithic catalysts for NRR. The electrocatalytic performance of xCNFP@GA-y were improved by adjusting the hydrophobicity of GA and electroplating voltage. In addition, the unique morphological features of x-CNFP@GA-y facilitate the exposure of a large number of active sites. The ammonia yield or FE of 0.2-CNFP@GA-0.3 was as high as 163.76 μg h–1 mgcat.–1 or up to 11.07% in 0.1 M HCl electrolyte at a potential of –0.24 V or –0.14 V vs reversible hydrogen electrode (V vs RHE), respectively. The reaction process of NRR was monitored using in situ Raman spectroscopy, and possible reaction pathway is proposed and discussed. The studies open a new window for the development of transition-metal based catalysts with low cost, high efficiency and excellent sustainability and recyclability in the field of NRR.