Facile synthesis of porous carbon/Ni12P5 composites for electrocatalytic hydrogen evolution

Water splitting into hydrogen (H-2) to produce clean energy is of great significance for sustainable development. Transition metal phosphides (e.g., Ni12P5 nanoparticles) may be used as non-precious earth-abundant electrocatalysts for the H-2 evolution reaction, but their poor electronic conductivity and small surface area hinder efficient catalytic H-2 production. In this research, we demonstrate for the first time the facile synthesis of porous carbon/Ni12P5 (C/NiP-C) composites with the dispersion of Ni12P5 nanoparticles onto a conductive porous carbon support in an ionic surfactant hexadecyl trimethyl ammonium bromide (CTAB)-mediated ethanol solution. The CTAB plays dual roles in the synthesis including (1) the introduction of carbon to increase the conductivity of the synthetic materials and (2) the formation of uniform Ni12P5 phosphides through the interaction between the H2PO2- anion, Ni2+, and C19H42N+ cation dissociated from CTAB. The obtained C/NiP-C composites may function as electrocatalysts for the hydrogen evolution reaction (HER) with excellent HER performance (: 63 mV, (10): 176 mV, Tafel slope: 100 mV dec(-1), wherein represents the onset overpotential and (10) represents the overpotential required for a current density (j) value of -10 mA cm(-2)) compared with the NixPy composites synthesized in pure ethanol (: 160 mV, (10): 392 mV, Tafel slope: 154 mV dec(-1)), the C/NiP-P composites synthesized in a P123-mediated ethanol solution (: 75 mV, (10): 286 mV, Tafel slope: 210 mV dec(-1)), and the C/NiP-F composites synthesized in a F127-mediated ethanol solution (: 80 mV, (10): 302 mV, Tafel slope: 189 mV dec(-1)). The enhanced HER performance can be attributed to the synergistic effects resulting from the unique structure of the porous C support and the well dispersed Ni12P5 nanoparticles.