A solar-driven CO2 reduction (CO2R) cell was constructed, consisting of a tandem GaAs/InGaP/TiO2/Ni photoanode in 1.0 M KOH(aq) (pH = 13.7) to facilitate the oxygen-evolution reaction (OER), a Pd/C nanoparticle-coated Ti mesh cathode in 2.8 M KHCO3(aq) (pH = 8.0) to perform the CO2R reaction, and a bipolar membrane to allow for steady-state operation of the catholyte and anolyte at different bulk pH values. At the operational current density of 8.5 mA cm-2, in 2.8 M KHCO3(aq), the cathode exhibited <100 mV overpotential and >94% Faradaic efficiency for the reduction of 1 atm of CO2(g) to formate. The anode exhibited a 320 ± 7 mV overpotential for the OER in 1.0 M KOH(aq), and the bipolar membrane exhibited ∼480 mV voltage loss with minimal product crossovers and >90 and >95% selectivity for protons and hydroxide ions, respectively. The bipolar membrane facilitated coupling between two electrodes and electrolytes, one for the CO2R reaction and one for the OER, that typically operate at mutually different pH values and produced a lower total cell overvoltage than known single-electrolyte CO2R systems while exhibiting ∼10% solar-to-fuels energy-conversion efficiency.
All Science Journal Classification (ASJC) codes
- Chemistry (miscellaneous)
- Renewable Energy, Sustainability and the Environment
- Fuel Technology
- Energy Engineering and Power Technology
- Materials Chemistry