NaCl template-directed approach to ultrathin lamellar molybdenum phosphide-carbon hybrids for efficient hydrogen production

Abstract

Molybdenum phosphide (MoP) is a prospective non-precious catalyst for hydrogen evolution reaction (HER), though its HER elctrocatalytic performance need to be further enhanced. We first report a facile, easy-scalable and low-cost approach for fabricating porous lamellar MoP/C hybrids by simply mixing the common ingredients of ammonium molybdate, ammonium dihydrogen phosphate, dicyandiamide and sodium chloride (NaCl), followed by freeze-drying, annealing and water-washing. Here, NaCl is used as pore-forming and template-directing agent during the high-temperature annealing and “cooling recrystallization” process. Highly crystalline and ultrafine MoP nanoparticles are intimately wrapped by lamellar carbon nanosheets. The lamellar conductive architecture with ultrathin and porous carbon nanosheets provides multiple attractive properties for HER, such as impeding the growth of nanoparticles, offering an expressway for boosting mass/charge transfer, and delivering large specific surface area with numerous exposed eletrocatalytic sites. Consequently, the MoP/C (NaCl) electrocatalyst presents a low HER overpotential of 118 mV at 10 mA cm−2 with a small Tafel slope of 50.7 mV dec−1 in 0.5 M H2SO4, as well as robust stability. Moreover, a home-made electrolyzer using MoP/C (NaCl) as cathode achieves 0.71 A cm−2 at 2 Vcell at 80 °C, and is operated stably for more than 3300 min at 150 mA cm−2.