Efficient photosynthesis of carbon monoxide from CO2 using perovskite photovoltaics

Abstract

Artificial photosynthesis, mimicking nature in its efforts to store solar energy, has received considerable attention from the research community. Most of these attempts target the production of H2 as a fuel and our group recently demonstrated solar-to-hydrogen conversion at 12.3% efficiency. Here, in an effort to take this approach closer to real photosynthesis, which is based on the conversion of CO2, we demonstrate the efficient reduction of CO2 to carbon monoxide driven solely by simulated sunlight using water as the electron source. Employing series-connected perovskite photovoltaics and high-performance catalyst electrodes, we reach a solar-to-CO efficiency exceeding 6.5%, which represents a new benchmark in sunlight-driven CO2 conversion. Considering hydrogen as a secondary product, an efficiency exceeding 7% is observed. Furthermore, this study represents one of the first demonstrations of extended, stable operation of perovskite photovoltaics, whose large open-circuit voltage is shown to be particularly suited for this process.

Figure 1. Sunlight-driven CO₂ reduction device.

(a) Schematic of the device combining photovoltaics with an electrochemical cell. (b) Generalized energy diagram for converting CO₂ into CO with three perovskite solar cells. The series-connected photovoltaics produce a voltage sufficient to overcome the sum of the reaction free energy (ΔE) and the reaction overpotentials (η) at the electrodes.

Figure 2. Characterization of CO₂ reduction and H₂O oxidation electrodes.

(a) Electrochemical performance and FE towards CO production of oxidized Au electrodes in CO₂-saturated aqueous solution of 0.5 M NaHCO₃. Error bars correspond to the s.d. of repeated gas measurements. (b) Electrochemical performance of IrO₂ towards water oxidation in solutions of 1.0 M NaOH and 0.5 M NaHCO₃ under Ar and CO₂ saturation.

Figure 3. Characterization of the complete device.

(a) J–V curves of three series-connected perovskite cells under simulated AM 1.5G 1 Sun solar irradiation and in the dark, overlaid with the matched J–V characteristic of the CO₂-reduction and oxygen-evolution electrodes. The maximum power point of the photovoltaics is designated with a dot. (b) Current density, CO yield and solar-to-CO conversion efficiency of the device during an 18-h stability test.