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Solar-Driven reduction of CO2 to formate at 10% efficiency
Zhou X. et al. Solar-Driven Reduction of 1 atm CO2 to Formate at 10% Energy-Conversion Efficiency by Use of a TiO2-Protected III-V Tandem Photoanode in Conjunction with Bipolar Membrane and a Pd/C Cathode Electrocatalyst. ACS Energy Letters, DOI: 10.1021/acsenergylett.6b00317 (2016).
Researchers constructed a cell that consisted of a tandem GaAs/InGaP/TiO2/Ni photoanode in 1.0M KOH (pH=13) that carried out an oxygen evolution reaction (OER) and a Pd/C nanoparticle-coated Ti mesh cathode in 2.8M KHCO3 (pH=8.0) that performed CO2 reduction reaction. The cell included a bipolar membrane that allowed for a steady-state operation of the catholyte and anolyte at different bulk pH values. At the operational current density of 8.5 mA cm–2, the cathode exhibited <100 mV overpotential and >94% Faradaic efficiency for CO2 reduction to formate , the anode exhibited a 320 ± 7 mV overpotential for OER , and the bipolar membrane exhibited a ∼480 mV voltage loss with minimal product crossovers and >90 and >95% selectivity for proton and hydroxide ions, respectively.
Under 1.0 Sun illumination, the cell exhibited a high solar-to-fuel conversion efficiency of 10%.
Reprinted with permission from Zhou X. et al. Solar-Driven Reduction of 1 atm CO2 to Formate at 10% Energy-Conversion Efficiency by Use of a TiO2-Protected III-V Tandem Photoanode in Conjunction with Bipolar Membrane and a Pd/C Cathode Electrocatalyst. ACS Energy Letters, DOI: 10.1021/acsenergylett.6b00317 (2016). Copyright American Chemical Society (2016).
(A) Schematic illustration of a two-electrode electrochemical setup. The blue tubes were connected to a peristaltic pumping system, which facilitated the removal of CO2 bubbles and prevented voltage loss caused by bubbles. (B) The unassisted CO2R current density as a function of operational time using a GaAs/InGaP/TiO2/Ni photoanode and a Pd/C-coated Ti mesh cathode in a two-electrode electrochemical configuration (panel A) under 100 mW cm–2 of simulated AM1.5 illumination. (C) The overall polarization characteristics for the CO2R reaction and the OER using a p+-Si/TiO2/Ni anode and a Pd/C-coated Ti mesh cathode in the two-electrode BMP configuration (KHCO3/Nafion/KOH) (black) as well as in the two-electrode Nafion membrane configuration (KHCO3/Nafion/KHCO3) (blue). The measured (red) and calculated (black) two-electrode current–voltage behavior of the GaAs/InGaP/TiO2/Ni photoanode wired to a Pd/C-coated Ti mesh cathode was measured under 100 mW cm–2 of simulated AM1.5 illumination. The calculated current density–voltage characteristic of the solid-state tandem cell (orange)