Figure 6.

(a) Schematic and photograph of the redox-medium-assisted CO₂ photovoltaic electrocatalytic reduction system containing a nickel-iron hydroxide electrode and a zinc/zincate redox with a gold nanocatalyst (adapted from ref. [116] with permission from Springer Nature). (b) Illustration of a WO₃ (photoanode)||Cu_xO (photocathode) system coupling with a dye-sensitized solar cell (adapted from ref. [117] with permission from Elsevier). (c) Schematic view of the dendritic nanostructured CuO material before (top) and after (bottom) CO₂ photovoltaic electrocatalytic reduction in 0.1 M CsHCO₃ (adapted from ref. [118] with permission from the National Academy of Sciences, USA). (d) Illustration of the solar-driven overall CO₂ splitting system with Co₂FeO₄ nanoarrays both as anode and cathode (adapted from ref. [119] with permission from Wiley-VCH). (e) Schematic illustration of the BiVO₄/perovskite/3D TiN-ClFDH biocatalytic tandem PEC system for unbiased, solar-driven formate production (adapted from ref. [120] with permission from Wiley-VCH).