1D Co6Mo6C-Based Heterojunctional Nanowires from Pyrolytically “Squeezing” PMo12/ZIF-67 Cubes for Efficient Overall Water Electrolysis

Abstract

The bi-transition-metal interstitial compounds (BTMICs) are promising for water electrolysis. The previous BTMICs are usually composed of irregular particles. Here, this work shows the synthesis of novel 1D Co₆Mo₆C-based heterojunction nanowires (1D Co/Co₆Mo₆C) with diameters about 50 nm and a length-to-diameter ratio about 20 for efficient water electrolysis. An interesting growth process based on pyrolytically “squeezing” PMo₁₂ (Phosphomolybdic acid)/ZIF-67 (Zeolitic Imidazolate Framework-67) cube precursor is demonstrated. The “squeezing” growth is related to the role of Mo species for isolating Co species. A series of tests and theoretical calculation show the mutual regulation of Co and Mo to optimize the electronic structure, accelerating H₂O dissociation and the reduction kinetics of H⁺. Additionally, the nanowires provide pathways for electron transfer and the transmission of reactants. Consequently, the 1D Co/Co₆Mo₆C exhibits high activity for hydrogen evolution reaction (η₁₀ of 31 mV) and oxygen evolution reaction (η₁₀ of 210 mV) in 1 m KOH. The electrolytic cell based on 1D Co/Co₆Mo₆C requires a low voltage of 1.43 V to drive 10 mA cm⁻². The catalyst also exhibits good HER performance in 1 m phosphate-buffered saline solution, exceeding Pt/C at a current density >42 mA cm⁻².