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.