The Water Oxidation Bottleneck in Artificial Photosynthesis: How Can We Get Through It? An Alternative Route Involving a Two‐Electron Process

Abstract

The state-of-the-art of research on artificial photosynthesis is briefly reviewed. Insights into how Nature takes electrons from water, the photon-flux density of sunlight, the time scale for the arrival of the next photon (electron-hole) at the oxygen-evolving complex, how Nature solves the photon-flux-density problem, and how we can get through the bottleneck of water oxidation are discussed. An alternate route for a two-electron process induced by one-photon excitation is postulated for getting through the bottleneck of water oxidation.

Recent Advances in the BiVO4 Photocatalyst for Sun-Driven Water Oxidation: Top-Performing Photoanodes and Scale-Up Challenges

“…Since a photochemical process would be necessary for water splitting to take place, there is still a need for accumulated stepwise one-electron transfers under very specific photon-flux-density conditions. The challenge lies in the difficulty involved in preserving an oxidized state in a desired microenvironment and in avoiding its quenching as it awaits the arrival of the next photon [10]. Several studies have been conducted to evaluate appropriate materials that can serve as efficient photoanodes in order to overcome this bottleneck [11][12][13][14].…”

Mechanism of Water Oxidation Catalyzed by a Dinuclear Ruthenium Complex Bridged by Anthraquinone

“…Four-electron water oxidation to dioxygen is, therefore, an essential process for artificial photosynthesis, while there are several types of reduction processes. Water oxidation is the so-called "bottleneck of artificial photosynthesis" because of the simultaneous transfer of four electrons and the relatively high equilibrium electrode potential (1.23 V vs. NHE at pH 0) [11]. Many complexes containing Ru, Mn, Ir, Fe, Cu, and Co have been reported as molecular water oxidation catalysts [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Microstructure Effects on the Water Oxidation Activity of Co3O4/Porous Silica Nanocomposites

“…Water oxidation is the most difficult halfreaction in water splitting, involving the transfer of four electrons and the formation of oxygen−oxygen bonds. 1−4 After many studies devoted to developing more efficient and economic water oxidation catalysts, 5 cobalt-based materials have been identified as some of the most promising due to their relative abundance, high activity, and stability. 2,6−8 The synthesis and size-dependent properties of cobalt-based catalysts for electrochemical oxygen evolution have been examined previously.…”