Efficient solar fuel production with a high-pressure CO2-captured liquid feed

We demonstrated an efficient solar photovoltaic-powered electrochemical CO2 reduction device with a high-pressure CO2-captured liquid feed. In an air-to-barrel picture, this device holds promise to avoid both high-temperature gaseous CO2 regeneration and high energy-cost gas product separation steps, while these steps are necessary for devices with a gaseous CO2 feed. To date, solar fuel production with a CO2-saturated liquid feed suffers from high over-potential to suppress the hydrogen evolution reaction and consequently, low solar-to-chemical (STC) energy conversion efficiency. Here, we presented a dis-tinct high-pressure operando strategy, i.e., we took extra advantage of the high pressure in catalyst syn-thesis besides in the period of the CO2 reduction reaction (CO2RR). The power of this strategy was demonstrated by a proof-of-concept device in which a representative copper catalyst was first synthe-sized in operando in a high-pressure (50 bar) CO2-saturated KHCO3 solution, and then this high-pressure CO2-captured liquid was converted to solar fuel using the operando synthesized Cu catalyst. This Cu catalyst achieved 95% CO2RR selectivity at the recorded low potential of-0.3 V vs. RHE enabled by the combination of operando facet engineering and oxide derivation. Furthermore, this device achieved a record-high STC efficiency of 21.6% under outdoor illumination, superior to other CO2- saturated liquid-fed devices, and compared favorably to gaseous CO2-fed devices. (C) 2022 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

Automated summary

We demonstrated an efficient solar photovoltaic-powered electrochemical CO2 reduction device that uses a high-pressure CO2-captured liquid feed. The device takes advantage of high pressure in both catalyst synthesis and the CO2 reduction reaction to achieve high selectivity and energy conversion efficiency.