Inducing oxygen deficiencies through amorphization in IrMoOx: A pathway to highly efficient acidicwater oxidation and water splitting

Despite the considerable potential of acidic proton exchange membrane water electrolyzers (PEMWEs) for cost-efficient hydrogen production, their acidic oxygen evolution reaction (OER) kinetics are dramatically more sluggish than that in alkaline, causing inferior activity and stability. Herein, we successfully synthesize the amorphous IrMoO_x catalyst, featuring disordered structure, oxygen deficiencies and an increased oxidation state of Ir species compared with commercial IrO₂. The amorphous IrMoO_x catalyst demonstrates exceptional bifunctional catalytic activities and durability in both hydrogen evolution reaction (HER) and OER in acid, accompanied with the ultralow overpotentials (29 and 235 mV) for the 10 mA cm⁻², respectively. Theoretical calculations reveal the existence of special IrO₄ planar structure within the amorphous IrMoO_x and illustrate that the introduced Mo and rich oxygen vacancies optimize d-band of metal species, thereby tuning rate-determining step and enhancing OER performances compared with commercial IrO₂. Furthermore, the IrMoO_x || IrMoO_x catalyst delivers the current density of 10 mV cm⁻² at ultralow voltage of 1.55 V, outperforming the commercial Pt/C || IrO₂ (1.76 V).