Near-infrared light-inducible Z-scheme overall water-splitting photocatalyst without an electron mediator

We facilely prepared a solid-state heterojunction photocatalyst in which silver vanadium oxide (Ag2V4O11) and zinc rhodium oxide (ZnRh2O4) as oxygen and hydrogen evolution photocatalysts, respectively, were directly connected to generate Ag2V4O11/ZnRh2O4. Ag2V4O11/ZnRh2O4 photocatalyzed overall pure-water splitting without any electron mediator under irradiation with near-infrared light at wavelengths of up to 910 nm. The key points are that the conduction bottom potential of Ag2V4O11 is almost the same as the valence band top potential of ZnRh2O4, and that the bandgaps of Ag2V4O11 and ZnRh2O4 are 1.4 and 1.2 eV, respectively.

Synthesis of a Gold-Inserted Iron Disilicide and Rutile Titanium Dioxide Heterojunction Photocatalyst via the Vapor-Liquid-Solid Method and Its Water-Splitting Reaction

A solid-state Z-scheme system is constructed whereby rutile titania (TiO₂) and beta-iron disilicide (β-FeSi₂) were combined to act as oxygen (O₂)- and hydrogen (H₂)-evolution photocatalysts, respectively, connected by gold (Au). β-FeSi₂ island grains with diameters in the 0.5-2 μm range were formed on the surface of Au-coated TiO₂ powder by the co-sputtering method. On the surface of TiO₂ powder, the Au-Si liquidus phase was obtained via a Au-Si eutectic reaction, which contributed to the selective deposition and crystallization of β-FeSi₂ island grains onto Au. After the loading of the H₂-evolution cocatalysts platinum and chromium oxide onto β-FeSi₂, the system obtained catalyzed the evolution of H₂ and O₂ in a stoichiometric ratio from pure water under ultraviolet light irradiation. The transfer of photoexcited electrons in the conduction band (CB) of β-FeSi₂ to Pt causes the reduction of protons to H₂, and the photogeneration of holes in the valence band (VB) of TiO₂ causes the oxidation of water to O₂. In addition, the photogenerated holes in the VB of β-FeSi₂ and the photoexcited electrons in the CB of TiO₂ combined with each other in the Au layer, affording the completion of the overall photocatalytic water-splitting.

An Overview of the Photocatalytic Water Splitting over Suspended Particles

The conversion of solar to chemical energy is one of the central processes considered in the emerging renewable energy economy. Hydrogen production from water splitting over particulate semiconductor catalysts has often been proposed as a simple and a cost-effective method for large-scale production. In this review, we summarize the basic concepts of the overall water splitting (in the absence of sacrificial agents) using particulate photocatalysts, with a focus on their synthetic methods and the role of the so-called “co-catalysts”. Then, a focus is then given on improving light absorption in which the Z-scheme concept and the overall system efficiency are discussed. A section on reactor design and cost of the overall technology is given, where the possibility of the different technologies to be deployed at a commercial scale and the considerable challenges ahead are discussed. To date, the highest reported efficiency of any of these systems is at least one order of magnitude lower than that deserving consideration for practical applications.

Z-Scheme Photocatalytic Systems for Solar Water Splitting

As the world decides on the next giant step for the renewable energy revolution, scientists have begun to reinforce their headlong dives into the exploitation of solar energy. Hitherto, numerous attempts are made to imitate the natural photosynthesis of plants by converting solar energy into chemical fuels which resembles the "Z-scheme" process. A recreation of this system is witnessed in artificial Z-scheme photocatalytic water splitting to generate hydrogen (H2). This work outlines the recent significant implication of the Z-scheme system in photocatalytic water splitting, particularly in the role of electron mediator and the key factors that improve the photocatalytic performance. The Review begins with the fundamental rationales in Z-scheme water splitting, followed by a survey on the development roadmap of three different generations of Z-scheme system: 1) PS-A/D-PS (first generation), 2) PS-C-PS (second generation), and 3) PS-PS (third generation). Focus is also placed on the scaling up of the "leaf-to-tree" challenge of Z-scheme water splitting system, which is also known as Z-scheme photocatalyst sheet. A detailed investigation of the Z-scheme system for achieving H2 evolution from past to present accompanied with in-depth discussion on the key challenges in the area of Z-scheme photocatalytic water splitting are provided.

Semi-biological approaches to solar-to-chemical conversion

This review provides an overview of the cross-disciplinary field of semi-artificial photosynthesis, which combines strengths of biocatalysis and artificial photosynthesis to develop new concepts and approaches for solar-to-chemical conversion.

Selective loading of platinum or silver cocatalyst onto a hydrogen-evolution photocatalyst in a silver-mediated all solid-state Z-scheme system for enhanced overall water splitting

Pt or Ag as a cocatalyst was selectively photo-deposited onto ZnRh₂O₄ in ZnRh₂O₄/Ag/Bi₄V₂O₁₁ and resulted in the enhancement of the overall water-splitting activity of the photocatalyst.

Photocatalytic Hydrogen Evolution via Water Splitting: A Short Review

Photocatalytic H2 generation via water splitting is increasingly gaining attention as a viable alternative for improving the performance of H2 production for solar energy conversion. Many methods were developed to enhance photocatalyst efficiency, primarily by modifying its morphology, crystallization, and electrical properties. Here, we summarize recent achievements in the synthesis and application of various photocatalysts. The rational design of novel photocatalysts was achieved using various strategies, and the applications of novel materials for H2 production are displayed herein. Meanwhile, the challenges and prospects for the future development of H2-producing photocatalysts are also summarized.

Particulate photocatalyst sheets based on non-oxide semiconductor materials for water splitting under visible light irradiation

Photocatalyst sheets active in visible-light-driven water splitting, potentially under irradiation of up to 600 nm, are developed.

Facile synthesis of a red light-inducible overall water-splitting photocatalyst using gold as a solid-state electron mediator

We have prepared a solid-state heterojunction photocatalyst, which can split pure water in nearly the entire range of visible light with wavelengths of up to 740 nm.

A visible-light-induced photoelectrochemical water-splitting system featuring an organo-photocathode along with a tungsten oxide photoanode

An extremely low-biased water-splitting reaction occurred in a system containing a WO₃ photoanode and organo-photocathode.