Valorizing biomass waste through photoelectrochemical (PEC) methodology provides an attractive strategy for generating H2 and value-added chemicals by enabling a carbon–neutral cycle. Herein, we present an investigation of a series of bismuth-based oxide-modified TiO2 as the photoanode for PEC valorization of cellulose in aqueous solution. The bismuth-based oxide was synthesized onto a TiO2 photoanode by a chemical bath deposition (CBD) method followed by heat treatments. The composition of the materials was adjusted by varying the concentration of the Cu2+ and Bi3+ precursors. The research shows that Bi2O3 effectively suppresses the water oxidation reaction over TiO2, a competitive side reaction in PEC cellulose oxidation, resulting in a Faradaic efficiency (FE) of 83.9 ± 4.9 % toward formate production. In contrast, unmodified TiO2 photoanode only exhibits a FE of 25.3 ± 3.7 %. On the other hand, the photoelectrode showed insufficient oxidative force for both water and cellulose oxidation by the surface modification of CuBi2O4.