Facile immobilization of polyoxometalates for low-cost molybdenum/tungsten phosphide nanoparticles on carbon black for efficient electrocatalytic hydrogen evolution

Abstract

Cheap and stable earth-abundant electrocatalysts for hydrogen evolution reaction (HER) is an urgent need to realize industrial production of hydrogen. Herein, we present a “1-methylimidazole-immobilization” method to fix molybdenum and tungsten precursors simultaneously on carbon black for preparation of hybrid molybdenum/tungsten phosphide (Mo-W-P) HER catalysts. The synthesis of Mo-W-P nanoparticles on carbon black was designed as two steps: immobilization and phosphorization. The Mo/W precursors, phosphotungstic acid (H₃PW₁₂O₄₀) and phosphomolybdic acid (H₃PMo₁₂O₄₀) were first fixed on carbon black by 1-methylimidazole, followed by subsequent calcination in air to form the Mo-W-O precursors, which were further phosphatized with red phosphorus at 850 °C in argon atmosphere to form the Mo-W-P nanoparticles. The HER performance can be effectively tuned by changing the atomic ratio of Mo/W, where the introduction of suitable amount of W into MoP results in dramatic decrease of the overpotential. The optimized sample with Mo/W ratio of 1.8:1 showed excellent electrocatalytic performance for HER with a low onset overpotential of 92 mV, along with a low Tafel slope of 62 mV dec⁻¹ in 0.5 M H₂SO₄. More importantly, at higher current density of 50 mA cm⁻², the optimized Mo-W-P/CB sample showed superior overpotential (231 mV) to that of MoP/CB (287 mV) and WP/CB (333 mV). Meanwhile, the Mo-W-P/CB hybrid nanoparticles also showed good stability and durability in strong acid electrolyte. Our work provides a route for construction of efficient hybrid electrocatalysts by immobilization of inorganic complexes.

Graphical Abstract

Keywords:

• Polyoxometalates
• molybdenum phosphide
• tungsten phosphide
• carbon black
• hydrogen evolution reaction

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is supported by the National Natural Science Foundation of China (grant nos. 21908081 and 21501072) and the Jiangsu Specially-Appointed Professors Program.