Over a 15.9% Solar-to-CO Conversion from Dilute CO₂ Streams Catalyzed by Gold Nanoclusters Exhibiting a High CO₂ Binding Affinity

Abstract

Development of efficient and selective electrocatalysts is a key challenge to achieve an industry-relevant electrochemical CO 2 reduction reaction (CO 2 RR) to produce commodity chemicals. Here, we report that Au 25 clusters with Authiolate staple motifs can initiate electrocatalytic reduction of CO 2 to CO with nearly zero energy loss and achieve a high CO 2 RR current density of 540 mA cm −2 in a gas-phase reactor. Electrochemical kinetic investigations revealed that the high CO 2 RR activity of the Au 25 originates from the strong CO 2 binding affinity, leading to high CO 2 electrolysis performance in both concentrated and dilute CO 2 streams. Finally, we demonstrated an 18.0% solar-to-CO conversion efficiency using a Au 25 electrolyzer powered by a Ga 0.5 In 0.5 P/GaAs photovoltaic cell. The electrolyzer also showed 15.9% efficiency and a 5.2% solar-driven single-path CO 2 conversion rate in a 10% CO 2 gas stream, the CO 2 concentration in a typical flue gas.

Modulating Local CO2 Concentration as a General Strategy for Enhancing C−C Coupling in CO2 Electroreduction

“…8,9 In order to overcome CO 2 mass transport issues, gas-diffusion electrodes (GDEs) have been employed in flow electrolyzers to achieve industrially relevant current densities (>200 mA cm À2 ). [10][11][12] However, transferring these high C 2+ product selectivity performances to GDE-based electrolyzers has been challenging without relying on alkaline electrolyte. [13][14][15] The use of alkaline electrolyte has raised concerns regarding the cost for electrolyte regeneration due to the continuous carbonation formation, which also causes stability issues.…”

Decoupling Strategy for Enhanced Syngas Generation from Photoelectrochemical CO2 Reduction

“…The efficiency is higher than recently reported values in a PEC cell without external bias ( Li et al., 2019 ; Andrei et al., 2020 ). Although the efficiency is lower than that reported in photovoltaic-electrolysis (PV-E) system ( Schreier et al., 2015a , 2017 ; Urbain et al., 2017 ; Zhang et al., 2019 ; Kim et al., 2019 ; Cheng et al., 2020 ), the PEC approach integrates the light harvesting and electrochemical process of PV-E process into a single and monolithic device via a direct semiconductor-electrolyte interface, providing potential advantages over the PV-E system in terms of cost and complexity. And it is expected that the STS efficiency of the PEC system could be enhanced further by employing better photoanode with higher photocurrent at the low bias region, which would improve the overlap of J-V curves between photocathode and photoanode.…”

Monolithic Photoelectrochemical CO2 Reduction Producing Syngas at 10% Efficiency

“…However, H 2 evolution is expected to dominate at such flow rates. Such findings suggest that low concentration CO 2 gas streams, such as air or flue gas, could be supplied to the cathode at 10 sccm, reducing the amount of CO 2 in the feed, [49] while limiting H 2 evolution by keeping the water content low. In this case, it would be necessary to employ a catalyst that prevents reactions of other components than CO 2 present in air or flue gas, such as the O 2 reduction reaction.…”

“…Reports of solar-driven CO 2 electrolyzers usually do not mention the CO 2 utilization efficiency, but it may be calculated from the published results and associated operating conditions. [49,52] Our calculations (Table S2, Supporting Information) show that many notable devices [24,26,27,29,31,49,[53][54][55][56] exhibit CO 2 utilization efficiencies below 1%. Given the clear relevance of CO 2 utilization efficiency to the field of (photo-)electrochemical CO 2 reduction, disclosure of this metric should become standard practice for future reports on CO 2 reduction devices.…”