A Tandem Photovoltaic-Electrochemical Photothermal Process for CO₂ Conversion to Butene

Decarbonizing the chemicals industry requires net carbon negative technologies capable of displacing current greenhouse gas emitting processes. In particular, the generation of valuable monomers, such as butene, are currently produced by significant greenhouse gas emitting processes, including ethylene oligomerization and crude oil refining, which require high temperatures and pressures. Integrated, tandem solar fuels devices for the conversion of CO 2 to ethylene, using solar-driven CO 2 reduction (CO 2 R), combined with a photothermal reactor for ethylene oligomerization, offers a potential path to producing clean butene from CO 2 , using solar energy as the only driving force. A key challenge for the successful operation of a tandem photo-driven electrochemical-photothermal system is the co-design of the two processes, which are typically optimized under different operating conditions. Specifically, photo-driven electrochemical CO 2 R (pCO 2 R) reactors operate under ambient temperature and pressure conditions while thermally-driven ethylene oligomerization reactors prefer elevated temperatures (80-140 °C) and pressures (30-150 atm) to promote high activity as well as pure ethylene in the inlet stream. Operation of the tandem process under solar-driven conditions imposes additional constraints on the maximum power output of the pCO 2 R reactor and the maximum temperature which can be obtained in the photothermal reactor. Herein, we present an unassisted solar-driven tandem system coupling pCO 2 R with photothermal ethylene oligomerization for the conversion of CO 2 to butene in a single pass. This work presents a critical advancement in the development of solar fuels technologies for larger hydrocarbon generation and identifies the co-design principles which must be considered for implementation of tandem, solar-driven electrochemical-thermal processes.