Integrated photovoltaic-electrochemical flow cell system design for solar-driven fuel production from carbon dioxide

Solar driven electrochemical reduction of carbon dioxide (CO₂) is emerging as one of the leading methods of closing the carbon cycle in chemical industries and harnessing abundant solar energy. An integrated photovoltaic (PV) electrochemical flow cell (EFC) system permits a modular approach to improving the overall conversion efficiency of solar energy to useful carbon-based products. In this thesis, an original membrane-type EFC is designed, assembled and tested for the reduction of CO₂ to carbon monoxide (CO). The design is based on the existing zero-gap, sandwich style models described in related work. This operational model is integrated with a high efficiency, triple junction, GaInP/GaAs/Ge PV cell that delivers suitable voltage to drive the reduction reaction. The EFC model incorporates an optimised flow region geometry for the working electrode compartment based on computational fluid dynamics (CFD) simulation. Optimisation of the flow region targets minimisation of stagnation and even distribution of flow across the electrode surface. Here, a peak overall solar-to-fuel efficiency of 3.1 % for reduction of CO₂ to CO is achieved. This is accomplished in a laboratory environment with an optimised reactant flow rate, electrolyte concentration and a deposition of a carbon nanotube (CNT) support layer to the working electrode.