Fast and Simple Construction of Efficient Solar-Water-Splitting Electrodes with Micrometer-Sized Light-Absorbing Precursor Particles

Micrometer-sized light-absorbing semiconductor particles (usually prepared by high temperature synthetic techniques) hold the desirable merits of high crystallinity, low concentrations of bulk defects, and a decreased grain boundary density to reduce bulk recombination of photocarriers. However, solar-water-splitting electrodes assembled using them as precursors always produce very low photocurrents. This could be due to the lack of an effective fabrication and/or modification protocol applicable to assemble these micrometer-sized semiconductor particles into suitable electrode configurations. A fast and simple fabrication scheme of drop-casting followed by the necking treatment is developed to enable the micrometer-sized precursor particles derived photoelectrodes to deliver appreciable photocurrent densities (>1 mA cm⁻²). By applying this fabrication scheme, photoelectrodes of solid-state reaction derived Mo doped BiVO₄ (≈4 μm, modified with oxygen evolution catalysts) and commercial WO₃ (size ranging from 100 nm to >10 μm) have yielded photocurrent densities higher than 1 mA cm⁻², while the photoelectrode composed of commercial CdSe (≈10 μm) is able to produce a photocurrent density higher than 5 mA cm⁻² (in a Na₂S aqueous solution). This strategy provides a new possible way, in addition to the predominant route of nanostructuring, to construct efficient solar-water-splitting electrodes.