Light-driven charge accumulation of a molecular Cu(I) complex for storage of photoredox equivalents. ChemRxiv. Preprint.The diurnal day/night cycle is presently of great interest for harvesting solar energy aimed at rendering suitable energy storage schemes. To this end we present a noble-metal free system based on a Cu(I) 4H-imidazolate complex, that is efficiently photoreduced in the presence of a sacrificial donor. The two-electron reduced species obtained can be stored in the dark for more than 14 hours. In a dark reaction, the photoredox equivalents can subsequently be transferred to the electron acceptors methyl viologen or oxygen, while the starting Cu(I) complex is almost completely regained. Repetition of this process revealed a charging capacity of 72% after four cycles. The implications of light-driven charge accumulation and prolonged storage times for solar battery and photoredox catalysis are discussed File list (2) download file view on ChemRxiv SupportInfo.pdf (2.15 MiB) download file view on ChemRxiv Manuscript.pdf (914.38 KiB) Supplementary InformationLight-driven charge accumulation of a molecular Cu(I) complex for storage of photoredox equivalents

A conductive polymer (poly(p-phenylenevinylene), PPV) was covalently modified with RuII complexes to develop an all-polymer photocathode as a conceptual alternative to dye-sensitized NiO, which is the current state-of-the-art photocathode in solar fuels research. Photocathodes require efficient light-induced charge-transfer processes and we investigated these processes within our photocathodes using spectroscopic and spectro-electrochemical techniques. Ultrafast hole-injection dynamics in the polymer were investigated by transient absorption spectroscopy and charge transfer at the electrode–electrolyte interface was examined with chopped-light chronoamperometry. Light-induced hole injection from the photosensitizers into the PPV backbone was observed within 10 ps and the resulting charge-separated state (CSS) recombined within ~ 5 ns. This is comparable to CSS lifetimes of conventional NiO-photocathodes. Chopped-light chronoamperometry indicates enhanced charge-transfer at the electrode–electrolyte interface upon sensitization of the PPV with the RuII complexes and p-type behavior of the photocathode. The results presented here show that the polymer backbone behaves like classical molecularly sensitized NiO photocathodes and operates as a hole accepting semiconductor. This in turn demonstrates the feasibility of all-polymer photocathodes for application in solar energy conversion.