Prospects of Sunlight Driven Air-to-Methanol Synthesis via CO2 Electrolysis
<p>The race to save planet earth has led to significant advancement in technologies for harvesting renewable energy, carbon capture and conversion. Futures scenarios are being envisioned where CO<sub>2</sub> is captured from air and converted to valuable fuels and chemicals, with methanol (MeOH) being the most coveted product. Here we assess two potential air-to-MeOH pathways that harvest solar power via concentrated photovoltaic (CPV) cells for direct air capture (DAC) of CO<sub>2</sub> and subsequent conversion to MeOH by exploiting CO<sub>2</sub> electrolysis. Specifically, we perform techno-economic and life-cycle analysis on single-step (direct CO<sub>2</sub>-to-MeOH electrolysis) and three-step (integration of H<sub>2</sub>O electrolysis, CO<sub>2</sub>-to-CO electrolysis, and hydrogenation reactor) air-to-MeOH routes. Our results indicate that in current scenario, the envisioned air-to-MeOH routes are not economically and environmentally compelling with high levelized costs of MeOH ~1180–1730 $/ton<sub>MeOH</sub> and CO<sub>2</sub> emissions of ~2.29–2.69 /ton<sub>MeOH</sub>. Using sensitivity analysis, we reveal targets for CPV capital cost ($290/kW), DAC capital cost ($375/(ton-CO<sub>2</sub>/year)), and electricity emission intensity (<275 kg-CO<sub>2</sub>/MWh) which will make the three-step route commercially and environmentally viable as a near-term technology. In contrast, direct CO<sub>2</sub>-to-MeOH electrolysis will need drastic performance improvement to be economically competitive, with required current densities >300 mA/cm<sup>2</sup>, energy efficiency >45% and stack stability >2 years. We hope this study will garner the key stakeholders to advance discussions about the cost and potential of this envisioned air-to-fuel technology. </p>