Methods, Mechanism, and Applications of Photodeposition in Photocatalysis: A Review.
TL;DR: For a variety of metals and semiconductors, an attempt is made to generalize observations in the literature on the effect of process conditions applied during photodeposition on (i) particle size distributions, (ii) oxidation states of the metals obtained, and (iii) consequences for photocatalytic activities.
Abstract: In this review, for a variety of metals and semiconductors, an attempt is made to generalize observations in the literature on the effect of process conditions applied during photodeposition on (i) particle size distributions, (ii) oxidation states of the metals obtained, and (iii) consequences for photocatalytic activities. Process parameters include presence or absence of (organic) sacrificial agents, applied pH, presence or absence of an air/inert atmosphere, metal precursor type and concentration, and temperature. Most intensively reviewed are studies concerning (i) TiO2; (ii) ZnO, focusing on Ag deposition; (iii) WO3, with a strong emphasis on the photodeposition of Pt; and (iv) CdS, again with a focus on deposition of Pt. Furthermore, a detailed overview is given of achievements in structure-directed photodeposition, which could ultimately be employed to obtain highly effective photocatalytic materials. Finally, we provide suggestions for improvements in description of the photodeposition methods applied when included in scientific papers.
Citations
More filters
TL;DR: 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.
Abstract: 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.
1,365 citations
TL;DR: In this paper, the basic principles, photocatalytic-reactor design, kinetics, key findings, and the mechanism of metal-doped TiO2 are comprehensively reviewed.
Abstract: Hydrogen (H2) production via photocatalytic water splitting is one of the most promising technologies for clean solar energy conversion to emerge in recent decades. The achievement of energy production from water splitting would mean that we could use water as a fuel for future energy need. Among the various photocatalytic materials, titanium dioxide (TiO2) is the dominant and most widely studied because of its exceptional physico-chemical characteristics. Surface decoration of metal/non-metal on TiO2 nanoparticles is an outstanding technique to revamp its electronic properties and enrich the H2 production efficiency. Metal dopants play a vital role in separation of electron-hole pairs on the TiO2 surface during UV/visible/simulated solar light irradiation. In this paper, the basic principles, photocatalytic-reactor design, kinetics, key findings, and the mechanism of metal-doped TiO2 are comprehensively reviewed. We found that Langmuir-Hinshelwood kinetic model is commonly employed by the researchers to demonstrate the rate of H2 production. Copper (Cu), gold (Au) and platinum (Pt) are the most widely studied dopants for TiO2, owing to their superior work function. The metal dopants can amplify the H2 production efficiency of TiO2 through Schottky barrier formation, surface plasmon resonance (SPR), generation of gap states by interaction with TiO2 VB states. The recent advances and important consequences of 2D materials, perovskites, and other novel photocatalysts for H2 generation have also been reviewed.
609 citations
TL;DR: An overview on the basic principles that govern electrocatalytic or photocatalytic CO2 reduction and their important performance metrics are discussed and perspectives on the opportunities and possible directions for future development of this field are presented.
Abstract: Increasing CO2 concentration in the atmosphere is believed to have a profound impact on the global climate. To reverse the impact would necessitate not only curbing the reliance on fossil fuels but also developing effective strategies capture and utilize CO2 from the atmosphere. Among several available strategies, CO2 reduction via the electrochemical or photochemical approach is particularly attractive since the required energy input can be potentially supplied from renewable sources such as solar energy. In this Review, an overview on these two different but inherently connected approaches is provided and recent progress on the development, engineering, and understanding of CO2 reduction electrocatalysts and photocatalysts is summarized. First, the basic principles that govern electrocatalytic or photocatalytic CO2 reduction and their important performance metrics are discussed. Then, a detailed discussion on different CO2 reduction electrocatalysts and photocatalysts as well as their generally designing strategies is provided. At the end of this Review, perspectives on the opportunities and possible directions for future development of this field are presented.
558 citations
TL;DR: In this paper, the state-of-the-art engineering of efficient photocatalysts for dinitrogen (N2) fixation toward NH3 synthesis is reviewed and the challenges, outlooks and future prospects at the forefront of this research platform are presented.
Abstract: The burgeoning development of ammonia (NH3) synthesis technology addresses the urgency of food intake required to sustain the population growth of the last 100 years. To date, NH3 has mostly been synthesized by the Haber–Bosch process in industry. Under the ever-increasing pressure of the fossil fuel depletion crisis and anthropogenic global climate change with continuous CO2 emission in the 21st century, research targeting the synthesis of NH3 under mild conditions in a sustainable and environment friendly manner is vigorous and thriving. Therefore, the focus of this review is the state-of-the-art engineering of efficient photocatalysts for dinitrogen (N2) fixation toward NH3 synthesis. Strenuous efforts have been devoted to modifying the intrinsic properties of semiconductors (i.e. poor electron transport, rapid electron–hole recombination and sluggish reaction kinetics), including nanoarchitecture design, crystal facet engineering, doping and heterostructuring. Herein, this review provides insights into the most recent advancements in understanding the charge carrier kinetics of photocatalysts with respect to charge transfer, migration and separation, which are of fundamental significance to photocatalytic N2 fixation. Subsequently, the challenges, outlooks and future prospects at the forefront of this research platform are presented. As such, it is anticipated that this review will shed new light on photocatalytic N2 fixation and NH3 synthesis and will also provide a blueprint for further investigations and momentous breakthroughs in next-generation catalyst design.
527 citations
TL;DR: This review hopes that this review will provide some inspiration for the future discovery of the single-atom photocatalysts, manifestly stimulating the development in this emerging research area.
Abstract: Single-atom photocatalysts have shown their compelling potential and arguably become the most active research direction in photocatalysis due to their fascinating strengths in enhancing light-harvesting, charge transfer dynamics, and surface reactions of a photocatalytic system. While numerous comprehensions about the single-atom photocatalysts have recently been amassed, advanced characterization techniques and vital theoretical studies are strengthening our understanding on these fascinating materials, allowing us to forecast their working mechanisms and applications in photocatalysis. In this review, we begin by describing the general background and definition of the single-atom photocatalysts. A brief discussion of the metal-support interactions on the single-atom photocatalysts is then provided. Thereafter, the current available characterization techniques for single-atom photocatalysts are summarized. After having some fundamental understanding on the single-atom photocatalysts, their advantages and applications in photocatalysis are discussed. Finally, we end this review with a look into the remaining challenges and future perspectives of single-atom photocatalysts. We anticipate that this review will provide some inspiration for the future discovery of the single-atom photocatalysts, manifestly stimulating the development in this emerging research area.
509 citations
References
More filters
TL;DR: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent.
Abstract: This critical review shows the basis of photocatalytic water splitting and experimental points, and surveys heterogeneous photocatalyst materials for water splitting into H2 and O2, and H2 or O2 evolution from an aqueous solution containing a sacrificial reagent Many oxides consisting of metal cations with d0 and d10 configurations, metal (oxy)sulfide and metal (oxy)nitride photocatalysts have been reported, especially during the latest decade The fruitful photocatalyst library gives important information on factors affecting photocatalytic performances and design of new materials Photocatalytic water splitting and H2 evolution using abundant compounds as electron donors are expected to contribute to construction of a clean and simple system for solar hydrogen production, and a solution of global energy and environmental issues in the future (361 references)
8,850 citations
TL;DR: For the first time, a multi-variables optimization approach is described to determine the optimum operation parameters so as to enhance process performance and photooxidation efficiency in the photocatalytic water treatment process.
Abstract: In recent years, semiconductor photocatalytic process has shown a great potential as a low-cost, environmental friendly and sustainable treatment technology to align with the “ zero ” waste scheme in the water/wastewater industry. The ability of this advanced oxidation technology has been widely demonstrated to remove persistent organic compounds and microorganisms in water. At present, the main technical barriers that impede its commercialisation remained on the post-recovery of the catalyst particles after water treatment. This paper reviews the recent R&D progresses of engineered-photocatalysts, photoreactor systems, and the process optimizations and modellings of the photooxidation processes for water treatment. A number of potential and commercial photocatalytic reactor configurations are discussed, in particular the photocatalytic membrane reactors. The effects of key photoreactor operation parameters and water quality on the photo-process performances in terms of the mineralization and disinfection are assessed. For the first time, we describe how to utilize a multi-variables optimization approach to determine the optimum operation parameters so as to enhance process performance and photooxidation efficiency. Both photomineralization and photo-disinfection kinetics and their modellings associated with the photocatalytic water treatment process are detailed. A brief discussion on the life cycle assessment for retrofitting the photocatalytic technology as an alternative waste treatment process is presented. This paper will deliver a scientific and technical overview and useful information to scientists and engineers who work in this field.
4,293 citations
TL;DR: This work synthesized uniform anatase TiO2 single crystals with a high percentage (47 per cent) of {001} facets using hydrofluoric acid as a morphology controlling agent and demonstrates that for fluorine-terminated surfaces this relative stability is reversed.
Abstract: [Yang, Hua Gui; Sun, Cheng Hua; Qiao, Shi Zhang; Liu, Gang; Smith, Sean Campbell; Lu, Gao Qing] Univ Queensland, ARC Ctr Excellence Funct Nanomat, Sch Engn, Brisbane, Qld 4072, Australia. [Yang, Hua Gui; Sun, Cheng Hua; Qiao, Shi Zhang; Liu, Gang; Smith, Sean Campbell; Lu, Gao Qing] Univ Queensland, Australian Inst Bioengn & Nanotechnol, Ctr Computat Mol Sci, Brisbane, Qld 4072, Australia. [Zou, Jin] Univ Queensland, Ctr Microscopy & Microanal, Brisbane, Qld 4072, Australia. [Zou, Jin] Univ Queensland, Sch Engn, Brisbane, Qld 4072, Australia. [Liu, Gang; Cheng, Hui Ming] Chinese Acad Sci, Met Res Inst, Shenyang Natl Lab Mat sci, Shenyang 110016, Peoples R China.;Lu, GQ (reprint author), Univ Queensland, ARC Ctr Excellence Funct Nanomat, Sch Engn, Brisbane, Qld 4072, Australia;s.qiao@uq.edu.au maxlu@uq.edu.au
3,656 citations
TL;DR: This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials, and highlights crucial issues that should be addressed in future research activities.
Abstract: Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.
3,265 citations
TL;DR: This review for the first time summarizes all the developed earth-abundant cocatalysts for photocatalytic H2- and O2-production half reactions as well as overall water splitting.
Abstract: Photocatalytic water splitting represents a promising strategy for clean, low-cost, and environmental-friendly production of H2 by utilizing solar energy. There are three crucial steps for the photocatalytic water splitting reaction: solar light harvesting, charge separation and transportation, and the catalytic H2 and O2 evolution reactions. While significant achievement has been made in optimizing the first two steps in the photocatalytic process, much less efforts have been put into improving the efficiency of the third step, which demands the utilization of cocatalysts. To date, cocatalysts based on rare and expensive noble metals are still required for achieving reasonable activity in most semiconductor-based photocatalytic systems, which seriously restricts their large-scale application. Therefore, seeking cheap, earth-abundant and high-performance cocatalysts is indispensable to achieve cost-effective and highly efficient photocatalytic water splitting. This review for the first time summarizes all the developed earth-abundant cocatalysts for photocatalytic H2- and O2-production half reactions as well as overall water splitting. The roles and functional mechanism of the cocatalysts are discussed in detail. Finally, this review is concluded with a summary, and remarks on some challenges and perspectives in this emerging area of research.
1,990 citations