Green Synthesis of Iron Phosphide Nanoparticles with High Catalytic Activity for Liquid-Phase Nitrile Hydrogenation

Abstract

Owing to the natural abundance, cost-effectiveness, and minimal environmental impact of iron, iron-based catalysts are widely recognized as promising. In this context, iron phosphide nanoparticles have recently attracted attention as a distinctive class of air-stable and highly active iron-based catalysts for liquid-phase hydrogenation reactions as well as electrochemical reactions. However, conventional synthesis methods typically require highly toxic iron and phosphorus sources such as Fe(CO)₅ and phosphine derivatives, posing severe practical and environmental concerns. In this study, we developed a safer and more environmentally friendly method for the synthesis of iron phosphide nanoparticles by utilizing iron carboxylates as non-toxic and readily available iron precursors and triphenylphosphite as a comparatively benign phosphorus source. This approach eliminates the need for hazardous reagents while allowing precise control over particle size and phase formation. By optimizing the iron precursor type, heating duration, temperature, and phosphorus amount, we selectively synthesized the Fe₂P phase under mild solvothermal conditions. Furthermore, the resulting Fe₂P nanoparticles exhibited twice the catalytic activity of those previously synthesized from Fe(CO)₅ in the liquid-phase hydrogenation of nitriles, highlighting the effectiveness of this green synthetic strategy. This method provides a practical and sustainable approach for the synthesis of catalytically active iron phosphide nanoparticles, potentially enabling their broader application in various catalytic and energy-related fields.