Large-scale printing synthesis of transition metal phosphides encapsulated in N, P co-doped carbon as highly efficient hydrogen evolution cathodes

The large-scale synthesis accompanying structural modulation of efficient noble-metal-free catalysts with facile kinetics for the hydrogen evolution reaction (HER) is still a big challenge for electrolytic water splitting. Herein, we report a simple inkjet printing technology for the large-scale synthesis of a series of transition metal phosphide (TMP) nanoparticles encapsulated in N, P co-doped carbon supported on carbon fiber cloth (CF@NPC-TMP, TM = Mo, Co, Ni, Fe) as highly efficient hydrogen evolution cathodes using ionic liquids as phosphorus and carbon sources. The in-situ carbon nanolayers derived from ionic liquids not only expose abundant catalytically active sites and allow rapid electron transport to the catalytically active sites during HER but also effectively prevent the TMP nanoparticles from corroding to enhance their stability. All the as-prepared CF@NPC-TMP electrodes show ideal electrocatalytic performance for HER. Especially, the CF@NPC-MoP electrode only requires overpotentials of 87 and 145 mV to drive cathodic current densities of 10 and 100 mA cm(-2) in 0.5M H2SO4, respectively. In addition, this electrode continuously operates at a constant current density of 10 mA cm(-2) for 20 h with negligible rise in operating potential. The resultant CF@NPC-TMP electrodes also show ideal electrocatalytic activities toward HER in alkaline and neutral media. Hence, the synthesis strategy developed in this study may spark interest in research on TMP-based nanomaterials for various applications.