Integrated photovoltaic-electrochemical system for carbon dioxide reduction

The rapid increase in carbon dioxide (CO₂) has recently become a social focus. Converting CO₂ to value-added fuels with CO₂ electrochemical reduction reaction (CO₂ERR) is an attractive method to reduce CO₂. Photovoltaic-electrochemical (PV-EC) integrated systems enable to drive CO₂ERR with renewable electricity. However, PV-EC integrated systems have different optimal conditions depending on systems configuration. The aim of this Master thesis is to design a PV-EC system with a voltage regulator component, which facilitates the system operating at the desired potential for CO₂ERR. Effects of various operating parameters were investigated. A maximum Faradaic efficiency of CO (FE_CO, 90%) was obtained under the optimal 1-h CO₂ERR conditions with a potential of -1.25V vs. NHE, a CO₂ flow rate of 20 mL/min, 0.5M KHCO₃ electrolyte in a reversely assembled flow cell. A stable FE_CO of ca. 95% was reached for a 4-h long electrolysis under the optimal conditions. When the electrolyser was driven by a silicon solar cell under the identical conditions, a FE_CO of 57% was achieved. The drop in FE_CO can be explained by the energy loss in between the PV and EC components. This thesis gives an insight to further improve PV-EC systems to be stably operated under optimal conditions.