The photoelectrochemical (PEC) production of syngas from water and CO2 represents an attractive technology towards a circular carbon economy. However, the high overpotential, low selectivity and cost of commonly employed catalysts pose challenges for this sustainable energy-conversion process. Here we demonstrate highly tunable PEC syngas production by integrating a cobalt porphyrin catalyst immobilized on carbon nanotubes with triple-cation mixed halide perovskite and BiVO4 photoabsorbers. Empirical data analysis is used to clarify the optimal electrode selectivity at low catalyst loadings. The perovskite photocathodes maintain selective aqueous CO2 reduction for one day at light intensities as low as 0.1 sun, which provides pathways to maximize daylight utilization by operating even under low solar irradiance. Under 1 sun irradiation, the perovskite–BiVO4 PEC tandems sustain bias-free syngas production coupled to water oxidation for three days. The devices present solar-to-H2 and solar-to-CO conversion efficiencies of 0.06 and 0.02%, respectively, and are able to operate as standalone artificial leaves in neutral pH solution.
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This work was supported by the Christian Doppler Research Association (Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development) and the OMV Group (E.R.). V.A. is grateful for the financial support from the Cambridge Trusts (Vice-Chancellor’s Award) and the Winton Programme for the Physics of Sustainability. B.R. was supported by the BBSRC (grant no. BB/K010220/1). XPS data collection was performed at the EPSRC National Facility for Photoelectron spectroscopy (‘HarwellXPS’), operated by Cardiff University and UCL under contract no. PR16195. We acknowledge D. S. Wright (University of Cambridge) for providing us the Co WOC precursor. We thank A. Dickerson (University of Cambridge) for the ICP-OES measurements. We are grateful to D. Achilleos (University of Cambridge) for help with XPS sample preparation and data analysis. We thank K. P. Sokol (University of Cambridge) for helpful advice on the O2 measurements, and K. P. Sokol and A. Wagner (University of Cambridge) for useful feedback on the manuscript.
The authors declare no competing interests.
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Andrei, V., Reuillard, B. & Reisner, E. Bias-free solar syngas production by integrating a molecular cobalt catalyst with perovskite–BiVO4 tandems. Nat. Mater. (2019) doi:10.1038/s41563-019-0501-6