High-Efficiency Water-Splitting Solar Cells with Low Diffusion Resistance Corresponding to Halochromic Pigments Interfacing with ZrO₂

ZrO₂ nanoparticle films coated with halochromic pigments are applied to water-splitting solar cells. On the basis of our results, ZrO₂ nanoparticle films coated with methyl orange have remarkable water-splitting properties. Under positive applied voltages and AM 1.5G irradiation, the highest hydrogen gas generation rate (1.8 mL/h·cm²) is measured for ZrO₂ nanoparticle films coated with methyl orange in 0.2 M H₂SO₄ water solution as electrolyte. As the electrolyte is changed from KHCO₃ water solution to the H₂SO₄ water solution, the interface resistance between ZrO₂ corresponding to halochromic pigments is reduced (from 107 to 11.7 ω·m) and the electron diffusion coefficient is raised (821.67%).