Durable photoelectrochemical CO₂ reduction with water oxidation using a visible-light driven molecular photocathode

Abstract

A durable molecular photocathode driving CO2 reduction with over 1200 of turnover number was developed by electropolymerization of Ru(ii) complexes. The cell with a suitable photoanode enabled CO2 reduction with H2O oxidation with no bias for 24 h.

Supramolecular photocatalysts fixed on the inside of the polypyrrole layer in dye sensitized molecular photocathodes: application to photocatalytic CO2 reduction coupled with water oxidation

“…8 Such photoelectrochemical cells, also known as articial Z-scheme cells, can be broadly classied into two groups, both of which feature n-type semiconductor photoanodes (e.g., CoO x -deposited BiVO 4 (ref. 12) and reduced SrTiO 3 (ref. 13)) for water oxidation.…”

“…[13][14][15] The systems of the second group feature dye-sensitized molecular photocathodes consisting of a p-type semiconductor and a supramolecular photocatalyst with redox photosensitizer and catalyst units connected to each other (Scheme 1b). [10][11][12] The redox photosensitizer unit absorbs light and then transfers an electron from the valence band of the p-type semiconductor to the catalyst unit, which reduces CO 2 . The hole produced in the valence band of the p-type semiconductor is lled with an electron from the n-type semiconductor photoanode, which photochemically draws up electrons from water.…”

“…Although the photoelectrochemical systems of the second group are very rare examples of the use of molecular photocatalysts for CO 2 reduction coupled with water oxidation, [10][11][12] these systems can potentially employ various redox photosensitizers with strong absorption in the visible region, which is advantageous for visible-light-driven photocathode construction. The dye-sensitized molecular photocathodes 16,17 initially reported by Meyers et al 18,19 and our groups [9][10][11] featured metal complex-based photocatalysts with anchoring groups such as -COOH and -PO 3 H 2 adsorbed on the electrode surface.…”

“…[24][25][26] However, this approach does not increase the visible light absorption of the photocathode. Methods of the second type rely on the introduction of a polymer layer, e.g., Meyers' 19 and our 12,27 groups employed the reductive electropolymerization of vinyl groups in the diimine ligands of metal complexes to afford a polymer layer that contained both the photosensitizer and catalyst units on the semiconductor electrode and, compared to the photoelectrode with only the anchoring groups described above, more strongly absorbed visible light owing to the accumulation of photosensitizer units. 19,[27][28][29][30][31][32] The reductive electropolymerization of molecular complexes on the dye-sensitized molecular photocathode also drastically suppressed the desorption of metal complexes from the electrode and enhanced the durability of photocatalysts for CO 2 reduction.…”

“…As a result, the incident photon-to-current conversion efficiencies (IPCEs) were 1.2% or less. 12 A photoelectrochemical cell comprising the dye-sensitized molecular photocathode fabricated by the reductive polymerization of vinyl groups and a CoO x /BiVO 4 photoanode was reported as the most robust photocatalytic system for CO 2 reduction with water without any external bias, with the photoenergy conversion efficiency (ECE) reaching 1.7 Â 10 À2 %. 12 The replacement of saturated hydrocarbon chains in photocathodes with conductive polymers is a promising way of reducing polymer layer resistance and increasing the efficiency of the dye-sensitized molecular photocathode.…”