Solar-driven N₂ fixation offers a green alternative to the highly energy-intensive Haber-Bosch process that releases more than 300 million metric tons of CO₂ annually to form NH₃. However, N₂-reducing photoelectrochemical (PEC) studies have not elucidated how an oxidation reaction affects the N₂ reduction reaction (NRR). Here, we report a bias-free PEC platform for N₂ reduction to NH₃ and H₂O oxidation to O₂ and H₂O₂. Under solar light, the molybdenum-doped bismuth vanadate-based photoanodes extract electrons from H₂O and transfer them to the silicon photovoltaic-wired hematite photocathode. The light-absorbing cathode receives the electrons to drive the NRR, which is influenced by the H₂O oxidation reaction's conditions. Furthermore, the integration of PEC NRR with H₂O₂-dependent biocatalytic oxyfunctionalization achieves simultaneous synthesis of valuable chemicals on both electrodes. This work presents the first example of a PEC NRR platform coupled with H₂O oxidation and H₂O₂-dependent oxygenation for unbiased chemical synthesis using N₂, H₂O, and sunlight.