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

Abstract

Photocatalytic reduction of CO₂ using water as a reductant and visible light as the energy source is an important target in artificial photosynthesis. In this study, we report a highly stable photoelectrochemical CO₂ reduction involving a new molecular photocathode comprising a NiO electrode and polymerized complexes of the Ru(II) photosensitizer and Ru(II) catalyst (NiO/PRu-poly-Ru-RuCAT1). CO and HCOOH were stably and selectively produced for over 100 h under visible light irradiation and a low bias. The turnover number of CO₂ reduction products exceeded 1200, which represents the highest durability reported for photoelectrochemical reactions using molecular photocathodes. Moreover, a connected system of the NiO/PRu-poly-Ru-RuCAT1 molecular photocathode and a CoO_x/BiVO₄ photoanode suitable for water oxidation facilitated stable CO₂ reduction with water as an electron donor and visible light as the energy source, with no bias for over 24 h. An energy conversion efficiency of 1.7 × 10⁻²% was obtained, which is the highest value reported for visible light driven systems utilizing a molecular photocatalyst for CO₂ reduction with water as the reductant.