Chlorophyll sensitized BiVO4 as photoanode for solar water splitting and CO2 conversion

Converting solar energy into valuable hydrogen and hydrocarbon fuels through photoelectrocatalytic water splitting and CO₂ reduction is highly promising in addressing the growing demand for renewable and clean energy resources. However, the solar-to-fuel conversion efficiency is still very low due to limited light absorption and rapid bulk recombination of charge carriers. In this work, we present chlorophyll (Chl) and its derivative sodium copper chlorophyllin (ChlCuNa), as dye sensitizers, modified BiVO₄ to improve the photoelectrochemical (PEC) performance. The photocurrent of BiVO₄ is surprisingly decreased after a direct sensitization of Chl while the sensitization of ChlCuNa obviously enhances photocurrent of BiVO₄ electrodes by improved surface hydrophilicity and extended light absorption. ChlCuNa-sensitized BiVO₄ achieves an improved H₂ evolution rate of 5.43 μmol h^-1 cm^-2 in water splitting and an enhanced HCOOH production rate of 2.15 μmol h^-1 cm^-2 in CO₂ PEC reduction, which are 1.9 times and 2.4 times higher than pristine BiVO₄, respectively. It is suggested that the derivative ChlCuNa is a more effective sensitizer for solar-to-fuel energy conversion and CO₂ utilization than Chl.