Development and Functionalization of Visible-Light-Driven Water-Splitting Photocatalysts

Abstract

With global warming and the depletion of fossil resources, our fossil fuel-dependent society is expected to shift to one that instead uses hydrogen (H2) as a clean and renewable energy. To realize this, the photocatalytic water-splitting reaction, which produces H2 from water and solar energy through photocatalysis, has attracted much attention. However, for practical use, the functionality of water-splitting photocatalysts must be further improved to efficiently absorb visible (Vis) light, which accounts for the majority of sunlight. Considering the mechanism of water-splitting photocatalysis, researchers in the various fields must be employed in this type of study to achieve this. However, for researchers in fields other than catalytic chemistry, ceramic (semiconductor) materials chemistry, and electrochemistry to participate in this field, new reviews that summarize previous reports on water-splitting photocatalysis seem to be needed. Therefore, in this review, we summarize recent studies on the development and functionalization of Vis-light-driven water-splitting photocatalysts. Through this summary, we aim to share current technology and future challenges with readers in the various fields and help expedite the practical application of Vis-light-driven water-splitting photocatalysts.

Deposition of triazine-based graphitic carbon nitrideviaplasma-induced polymerisation of melamine

“…The overall redox process for light-induced water splitting on the catalyst surface can be divided into two half reactions: (i) the hole-driven oxidation of water into oxygen and protons (2H 2 O + 4h + → 4H + + O 2 , oxygen evolution reaction, OER) and (ii) the electron-driven reduction of protons to molecular hydrogen (2H + + 2e − → H 2 , hydrogen evolution reaction, HER). 91,92…”

“…The overall redox process for light-induced water splitting on the catalyst surface can be divided into two half reactions: (i) the hole-driven oxidation of water into oxygen and protons (2H 2 O + 4h + / 4H + + O 2 , oxygen evolution reaction, OER) and (ii) the electron-driven reduction of protons to molecular hydrogen (2H + + 2e À / H 2 , hydrogen evolution reaction, HER). 91,92 To enable both the OER and HER reactions with satisfactory efficiency, one crucial property of the photocatalyst is the existence of an adequate band gap (for light harvesting) with appropriate band-edge potentials. Firstly, for efficient photocatalytic water splitting, the band gap of the photocatalyst should ideally be about 2.0-2.2 eV 93,94 with a conduction-band minimum that is more negative than the reduction potential of the proton (À0.41 V vs. NHE, pH 7) and a valence-band maximum that is more positive than the oxidation potential of water (+0.82 V vs. NHE, pH 7).…”

Metal-nanocluster science and technology: my personal history and outlook

“…As described in Section 5, it has recently become possible to control the number of constituent atoms and chemical composition of the loaded metal NCs on the support using ligand-protected metal NCs as a precursor. 332 However, the method involves removal of the ligands by calcination at high temperature, which wastes energy. This waste of energy might become a hindrance to industrial application of metal NCs.…”

Efficient Removal of Methylene Blue and Ciprofloxacin from Aqueous Solution Using Flower-like, Nanostructured ZnO Coating under UV Irradiation

“…Co-catalysts, such as Pt, NiO and RuO 2 , are usually loaded on the photocatalyst surface in order to confine the photo-excited charge carriers to the surface, thus avoiding the charge recombination and introducing new active sites [35]. Another strategy to reduce the recombination of the photogenerated charges is to separate the electrons and holes by using different facets of the crystal photocatalyst [36] or by using a one-dimensional nanostructured photocatalyst [37]. When using one-dimensional nanostructures, such as nanorods or nanowires, photo-excited electrons migrate along the nanostructure axis towards the tip, while the holes migrate towards the sides, leading to effective separation of the photogenerated charges.…”