Direct air capture of CO2 for solar fuels production in flow

Abstract

Direct air capture is an emerging technology to decrease atmospheric CO2 levels, but it is currently costly and the long-term consequences of CO2 storage are uncertain. An alternative approach is to utilise atmospheric CO2 on-site to produce value-added renewable fuels, but current CO2 utilisation technologies predominantly require a concentrated CO2 feed or high temperature. Here, we report a gas-phase dual-bed direct air carbon capture and utilisation flow reactor that produces syngas (CO + H2) through on-site utilisation of air-captured-CO2 using light without requiring high temperature or pressure. The reactor consists of a solid silica-amine adsorbent to capture aerobic CO2 and produce CO2-free air; concentrated light is used to release the captured CO2 and convert it to syngas over a bed of a silica/alumina-titania-cobalt bis(terpyridine) molecular-semiconductor photocatalyst. We use the oxidation of depolymerised poly(ethylene terephthalate) plastics as the counter-reaction. We envision this technology to operate in a diurnal fashion where CO2 is captured during night-time and converted to syngas under concentrated sunlight during the day.