International audienceNi electrodeposited on n-type Si from aqueous solutions in the form of isolated or coalescent nanoparticles (NPs) protects the underlying and partially exposed Si from photocorrosion-induced electrical passivation. Such photoanodes, fabricated without the need for additional protecting layers, a buried junction, and high vacuum techniques, show a high photovoltage of similar to 500 mV for the oxygen evolution reaction (OER), state-of-the-art photocurrents, and faradaic efficiencies > 90% under AM 1.5G illumination conditions at pH 14. Remarkably, these photoelectrodes are stable and can be operated at the light limited catalytic current from 10 h to more than 40 h in 1 M NaOH. These findings demonstrate that robust and efficient Si-based photoanodes can be produced easily, which opens new opportunities for the implementation of low-cost Si-based monolithic photoelectrochemical cells for efficient solar fuel production

In spite of the notorious instability of Si in alkaline solutions, Si partially covered with hemispherical Ni particles show striking performances for sunlight-assisted water oxidation.