Self-Supported α-MoB/β-MoB2 Ceramic Electrodes for Efficient High-Current-Density Hydrogen Evolution in Acidic, Neutral, and Alkaline pH-Values

This paper describes the production and high-current-density hydrogen evolution reaction (HER) performance in the whole pH range (from acidic to basic pH values) of self-supported α-MoB/β-MoB₂ ceramic electrodes, aiming for use in industrial electrocatalytic water splitting. Tape-casting and phase-inversion process, followed by sintering, were employed to synthesize self-supported β-MoB₂ ceramic electrodes, which exhibited well arranged large finger-like pores, providing numerous active sites and channels for electrolyte entry and hydrogen release. The reaction between β-MoB₂ and the sintering aid of MoO₃ in situ produces α-MoB/β-MoB₂ heterojunctions, which significantly improve the electrocatalytic performance. At a current density of 1000 mA·cm^–2, the ceramic electrode manifested an overpotential of 289 mV and 294 mV in acidic and alkaline aqueous solutions, respectively, and a stable operation over time (>100 h). The electrode also performed well in a neutral solution, with an overpotential of 354 mV at 100 mA·cm^–2. Theoretical (DFT) calculations demonstrated that the α-MoB/β-MoB₂ heterojunction alters the electronic configuration of β-MoB₂, favoring an effective electron transfer mechanism; thereby, the adsorption free energy of hydrogen ions is close to zero, and the adsorption and dissociation of water molecules under alkaline and neutral conditions are significantly enhanced.