Photoelectrochemical (PEC) systems have been researched for decades for their great promise to convert sunlight to fuels. Majority of the research on PEC has been focusing on using light to split water to hydrogen and oxygen, and its performance is limited due to the need of additional bias. Another research direction on PEC focuses on using light to decompose organic materials while producing electricity. In this work, we report a new type of unassisted PEC system that uses light, water and oxygen to simultaneously produce electricity and valuable hydrogen peroxide (H2O2) on both photoanode and cathode, i.e., light + 2H2O + O2 = electricity + 2H2O2. This new PEC system is essentially a light-driven fuel cell with H2O2 as the main product on both electrodes, and it consists of BiVO4 photoanode where water is oxidized to H2O2 and carbon cathode where O2 is reduced to H2O2. In addition to producing H2O2, this PEC system also generates electricity, achieving a maximum power density of 0.194mW/cm2, an open circuit voltage of 0.61V, and a short circuit current density of 1.09mA/cm2. The electricity output can be further used as a sign for cell function when accompanied by a detector such as an LED light or a multimeter. This is the first work that shows H2O2 two-side generation with strict key factors study on such system, with clear demonstration on electricity output ability for it using low-cost earth abundant materials on both sides, which represents an exciting new direction for PEC systems.