S-Scheme Heterojunction Photocatalyst

Photoreduction of CO2 into sustainable and green solar fuels is generally believed to be an appealing solution to simultaneously overcome both environmental problems and energy crisis. The low selectivity of challenging multi-electron CO2 photoreduction reactions makes it one of the holy grails in heterogeneous photocatalysis. This Review highlights the important roles of cocatalysts in selective photocatalytic CO2 reduction into solar fuels using semiconductor catalysts. A special emphasis in this review is placed on the key role, design considerations and modification strategies of cocatalysts for CO2 photoreduction. Various cocatalysts, such as the biomimetic, metal-based, metal-free, and multifunctional ones, and their selectivity for CO2 photoreduction are summarized and discussed, along with the recent advances in this area. This Review provides useful information for the design of highly selective cocatalysts for photo(electro)reduction and electroreduction of CO2 and complements the existing reviews on various semiconductor photocatalysts.

Cocatalysts for Selective Photoreduction of CO2 into Solar Fuels.

Direct Z-scheme photocatalysts: Principles, synthesis, and applications

Review on the improvement of the photocatalytic and antibacterial activities of ZnO

In recent years, heterogeneous photocatalysis has received much research interest because of its powerful potential applications in tackling many important energy and environmental challenges at a global level in an economically sustainable manner. Due to their unique optical, electrical, and physicochemical properties, various 2D graphene nanosheets-supported semiconductor composite photocatalysts have been widely constructed and applied in different photocatalytic fields. In this review, fundamental mechanisms of heterogeneous photocatalysis, including thermodynamic and kinetics requirements, are first systematically summarized. Then, the photocatalysis-related properties of graphene and its derivatives, and design rules and synthesis methods of graphene-based composites are highlighted. Importantly, different design strategies, including doping and sensitization of semiconductors by graphene, improving electrical conductivity of graphene, increasing eloectrocatalytic active sites on graphene, strengthening interface coupling between semiconductors and graphene, fabricating micro/nano architectures, constructing multi-junction nanocomposites, enhancing photostability of semiconductors, and utilizing the synergistic effect of various modification strategies, are thoroughly summarized. The important applications including photocatalytic pollutant degradation, H2 production, and CO2 reduction are also addressed. Through reviewing the significant advances on this topic, it may provide new opportunities for designing highly efficient 2D graphene-based photocatalysts for various applications in photocatalysis and other fields, such as solar cells, thermal catalysis, separation, and purification.

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Graphene in Photocatalysis: A Review

Semiconductor photocatalysis is recognized as a promising strategy to simultaneously address energy needs and environmental pollution. Titanium dioxide (TiO2 ) has been investigated for such applications due to its low cost, nontoxicity, and high chemical stability. However, pristine TiO2 still suffers from low utilization of visible light and high photogenerated-charge-carrier recombination rate. Recently, TiO2 photocatalysts modified by dual cocatalysts with different functions have attracted much attention due to the extended light absorption, enhanced reactant adsorption, and promoted charge-carrier-separation efficiency granted by various cocatalysts. Recent progress on the component and structural design of dual cocatalysts in TiO2 photocatalysts is summarized. Depending on their components, dual cocatalysts decorated on TiO2 photocatalysts can be divided into the following categories: bimetallic cocatalysts, metal-metal oxide/sulfide cocatalysts, metal-graphene cocatalysts, and metal oxide/sulfide-graphene cocatalysts. Depending on their architecture, they can be categorized into randomly deposited binary cocatalysts, facet-dependent selective-deposition binary cocatalysts, and core-shell structural binary cocatalysts. Concluding perspectives on the challenges and opportunities for the further exploration of dual cocatalyst-modified TiO2 photocatalysts are presented.

Dual Cocatalysts in TiO 2 Photocatalysis.

Enhanced photocatalytic H2-production activity of WO3/TiO2 step-scheme heterojunction by graphene modification

The photocatalytic hydrogen production using solar energy through water splitting has received great attention due to the increasingly serious energy crisis. Herein, we report the controlled preparation of anatase TiO2 nanosheet photocatalyst by selectively depositing Co3O4 nanoparticles (NPs) as water oxidation cocatalyst (WOC) and Pt NPs as water reduction cocatalyst (WRC) on {001} and {101} facets, respectively, using a two-step photodeposition method. The prepared TiO2-Co3O4-Pt composite photocatalyst exhibits a greatly enhanced photocatalytic H2-production activity at the optimal weight percentage of Co3O4 and Pt (both 1.0 wt%), exceeding that of TiO2 nanosheet deposited with single Co3O4 or Pt cocatalyst by 9.4 and 1.8 times, respectively. The enhanced H2-production activity is due to the synergetic effect of surface heterojunction between {001} and {101} facets and selective deposition of Co3O4 and Pt dual-cocatalysts at {001} and{101} facets, respectively. The former is beneficial for the transfer and separation of charge carriers, the latter can reduce the recombination rate of photogenerated electrons and holes and also catalyze the redox reactions. This work will provide a new route for the rational design and fabrication of highly efficient photocatalysts with dual-cocatalysts through selective surface deposition.

Enhanced photocatalytic H 2 -production activity of anatase TiO 2 nanosheet by selectively depositing dual-cocatalysts on {101} and {001} facets

Introducing plasmonic metal onto semiconductor materials has been proven to be an attractive strategy for enhancing the photocatalytic activity in the visible region by tuning the morphologies, sizes and compositions of plasmonic metal to form the strong surface plasmon resonance Here we utilized the structure effect of reduced graphene oxide (rGO) to construct highly efficient plasmonic photocatalysts for the photocatalytic oxidation of pollutants Plasmonic Ag/Ag2CO3-rGO was facilely prepared by the spontaneous redox of Ag+ and the defect structures of rGO Characterization and photocatalytic tests showed that defect structures of rGO promoted the formation of plasmonic Ag, and graphitic structures reduced the recombination rate of photogenerated electrons and holes Thus, the as-constructed Ag/Ag2CO3-rGO photocatalysts exhibited a much higher photocatalytic activity than the Ag2CO3 and Ag2CO3-GO-10 composite in the photocatalytic oxidation of organic pollutant, and the Ag/Ag2CO3-rGO (10 wt% rGO) showed the optimum photocatalytic performance This work may lead to a new strategy for exploring the advanced photocatalysts of semiconductors and rGO composite by utilizing the structures of rGO for the photocatalytic elimination of pollutants

Structure effect of graphene on the photocatalytic performance of plasmonic Ag/Ag2CO3-rGO for photocatalytic elimination of pollutants

Photocatalytic CO2 conversion into solar fuels has an alluring prospect. However, the rapid recombination of photogenerated electron–hole pairs for TiO2-based photocatalyst hinders its wide applica...

Aiyun Meng

Papers

Dual Cocatalysts in TiO 2 Photocatalysis.

Enhanced photocatalytic H2-production activity of WO3/TiO2 step-scheme heterojunction by graphene modification

Enhanced photocatalytic H 2 -production activity of anatase TiO 2 nanosheet by selectively depositing dual-cocatalysts on {101} and {001} facets

Structure effect of graphene on the photocatalytic performance of plasmonic Ag/Ag2CO3-rGO for photocatalytic elimination of pollutants

TiO2–MnOx–Pt Hybrid Multiheterojunction Film Photocatalyst with Enhanced Photocatalytic CO2-Reduction Activity