Molecular-based dye-sensitized photoelectrochemical cells (DSPECs) have traditionally targeted solar-driven water splitting for the conversion of solar energy into fuels in aqueous media. Here we describe a novel approach to develop the DSPECs by combining hydrogen atom transfer mediator (HAT) with nanostructured semiconductors and photocatalysts for photocatalytic C−C/C−O bonds cleavage in lignin. This work reports the application of the DSPEC specifically designed to carry out photocatalytic oxidative cleavage of C−C/C−O σ-bonds in lignin model compounds at the photoanode. Current studies targeting the development of photocatalysts via HAT process for biomass conversion especially lignin depolymerization will be described, with the novel finding that a DSPEC utilizes a solar-driven catalytic conversion of woody biomass into value-added fuels and chemicals under aerobic mild conditions. The efficient photocatalytic bond cleavage in DSPECs is important to the development of sustainable approaches for lignin depolymerization and biomass conversion.