A Fully Artificial Molecular-Based Photoelectrochemical Cell Enabling Overall Water Splitting by Combining a Photoanode and a Dark-Cathode

Significant efforts have been made to develop molecular-based artificial photosynthetic systems for overall solar water splitting by carefully functionalizing the photoelectrochemical cells with various molecular components serving as photosensitizers (PSs), water oxidation catalysts (WOCs), and water reduction catalysts (WRCs). Nevertheless, the development of fully artificial photosynthetic systems efficiently promoting overall solar water splitting remains a great challenge. In this study, a fully artificial molecular-based photoelectrochemical cell (MPEC) is constructed by utilizing the mesoporous TiO2 photoanode anchored with both a polypyridyl ruthenium PS and a ruthenium-based WOC, while the mesoporous TiO2 dark-cathode is anchored with a platinum porphyrin WRC. Only by visible-light irradiation at the photoanode, our MPEC promotes water splitting into H2 and O2 in a 2:1 molar ratio with almost quantitative Faradaic efficiencies. The applied-bias-compensated solar-to-hydrogen (AB-STH) conversion efficiency achieved herein (0.06%) is the highest value among the fully artificial MPECs reported to date. The present study also points out the importance of recalling the need to fabricate photosynthetic systems enabling the overall water splitting using a single photoreaction step without adopting the Z-scheme strategy.