Mimicking Natural Photosynthesis: Solar to Renewable H₂ Fuel Synthesis by Z-Scheme Water Splitting Systems

Abstract

Visible light-driven water splitting using cheap and robust photocatalysts is one of the most exciting ways to produce clean and renewable energy for future generations. Cutting edge research within the field focuses on so-called “Z-scheme” systems, which are inspired by the photosystem II–photosystem I (PSII/PSI) coupling from natural photosynthesis. A Z-scheme system comprises two photocatalysts and generates two sets of charge carriers, splitting water into its constituent parts, hydrogen and oxygen, at separate locations. This is not only more efficient than using a single photocatalyst, but practically it could also be safer. Researchers within the field are constantly aiming to bring systems toward industrial level efficiencies by maximizing light absorption of the materials, engineering more stable redox couples, and also searching for new hydrogen and oxygen evolution cocatalysts. This review provides an in-depth survey of relevant Z-schemes from past to present, with particular focus on mechanistic breakthroughs, and highlights current state of the art systems which are at the forefront of the field.

Efficient visible light-driven water oxidation and proton reduction by an ordered covalent triazine-based framework

“…ATR-FTIR spectroscopy was performed using a Perkin-Elmer 1605 FT-IR spectrometer in ATR mode with a range from 400-4000 cm À1 . 13 C cross-polarisation magic angle spinning (CPMAS) solid-state nuclear magnetic resonance (ssNMR) spectra were collected at ambient temperature on a BRUKER Advance 300 WB spectrometer (Bruker UK Ltd) with a 4 mm magic-angle spinning probe. X-ray photoelectron spectroscopy (XPS) was performed on a Thermo Scientific XPS K-alpha machine using monochromatic Al-Ka radiation.…”

“…7,8 Compared with the above single photocatalyst a Department of Chemical Engineering, University College London, Torrington Place, for pure water splitting, a Z-scheme composed of two photocatalysts responsible for two half reactions promises 10% higher solar-to-fuel conversion efficiency. [9][10][11][12][13] Therefore, substantial efforts have recently been channeled into searching for efficient polymer photocatalysts for either proton reduction or water oxidation in an attempt to construct an efficient Z-scheme system. Therein, water oxidation has been widely accepted as the rate-determining step in water splitting, and thus it is more challenging and important than proton production.…”

Bandgap Engineering of Organic Semiconductors for Highly Efficient Photocatalytic Water Splitting

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activity is highly dependent on the electronic structure of the photocatalyst, it is crucial to adjust the bandgap in order to utilize the highest possible proportion of visible photons and achieve the target of 10% solar to fuel conversion efficiency. [3][4][5][6][7][8] A Z-Scheme requires an appropriate match of redox potentials between two photocatalysts and two mediators. [3][4][5][6][7][8] A Z-Scheme requires an appropriate match of redox potentials between two photocatalysts and two mediators.

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Current perspectives in engineering of viable hybrid photocathodes for solar hydrogen generation

“…Actually, several configurations have been proposed for construction of such a PEC [6][7][8]. Among these configurations, the Z-scheme dual-photoelectrodes represents the most challenging one.…”

“…In this article, we review the current trenches being developed in engineering of viable hybrid photocathodes for the hydrogen generation. The current development of photoanodes could be referred to several articles published elsewhere [7,[19][20][21][22][23]. We first describe the principal operation of a hybrid photocathode composed of a light harvester and a H 2 -evolving catalyst.…”