Selective and Efficient Gd-Doped BiVO ₄ Photoanode for Two-Electron Water Oxidation to H ₂ O ₂

Photoelectrochemical oxidation of water presents a pathway for sustainable production of hydrogen peroxide (H ₂ O ₂ ). Two-electron water oxidation toward H ₂ O ₂ , however, competes with the popular four-electron process to form oxygen and one-electron water oxidation to form OH radical. To date, bismuth vanadate (BiVO ₄ ) has been shown to exhibit promising selectivity toward H ₂ O ₂ , especially under illumination, but it suffers from high overpotential and notoriously poor stability. Herein, using density functional theory calculations, we predict that doping BiVO ₄ with optimal concentrations of gadolinium (Gd) not only enhances its activity for H ₂ O ₂ production but also improves its stability. Experimentally, we demonstrate that intermediate amounts of Gd doping (6-12%) reduce the onset potential of BiVO ₄ for H ₂ O ₂ production by ∼110 mV while achieving a Faradaic efficiency of ∼99.5% under illumination and prolonging the catalytic lifetime by more than a factor of 20 at 2.0 V vs RHE under illumination.