Query: Direct splitting of water under visible light irradiation with an oxide semiconductor photocatalyst

Candidate papers:

abstract: The photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting, or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide, were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light, which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium tantalum oxide with nickel yields a series of photocatalysts, In1 xNixTaO4 (x 0 0.2) which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66% Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.
author_names: Zhi-gang Zou

Jinhua Ye

Kazuhiro Sayama

Hironori Arakawa
title: Direct splitting of water under visible light irradiation with an oxide semiconductor photocatalyst
venue: Nature
year: 2001

abstract: The photocatalytic splitting of water into hydrogen and oxygen using solar energy is a potentially clean and renewable source for hydrogen fuel. The first photocatalysts suitable for water splitting, or for activating hydrogen production from carbohydrate compounds made by plants from water and carbon dioxide, were developed several decades ago. But these catalysts operate with ultraviolet light, which accounts for only 4% of the incoming solar energy and thus renders the overall process impractical. For this reason, considerable efforts have been invested in developing photocatalysts capable of using the less energetic but more abundant visible light, which accounts for about 43% of the incoming solar energy. However, systems that are sufficiently stable and efficient for practical use have not yet been realized. Here we show that doping of indium tantalum oxide with nickel yields a series of photocatalysts, In(1 x)Ni(x)TaO(4) (x 0 0.2) which induces direct splitting of water into stoichiometric amounts of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66% Our findings suggest that the use of solar energy for photocatalytic water splitting might provide a viable source for 'clean' hydrogen fuel, once the catalytic efficiency of the semiconductor system has been improved by increasing its surface area and suitable modifications of the surface sites.
author_names: Zhi-gang Zou

Jinhua Ye

Kazuhiro Sayama

Hironori Arakawa
title: Direct Splitting of Water under Visible Light Irradiation with an Oxide Semiconductor Photocatalyst.
year: 2002

abstract: The photocatalytic splitting of water into hydrogen and oxygen using solar energy is one of the most attractive renewable sources of hydrogen fuel. Therefore, considerable efforts have been paid in developing photocatalysts capable of using visible light, which accounts for about 43% of the solar energy. However such a photocatalyst has not been developed so far. We have developed a new Ni doped indium tantalum oxide photocatalyst, In1 x Nix TaO4 (x 0.0~0.2) which induced direct splitting of water into stoichiometric amount of oxygen and hydrogen under visible light irradiation with a quantum yield of about 0.66% at 420.7 nm. We have also developed a new two step water splitting system using two different semiconductor photocatalysts, Pt/WO3 photocatalyst for oxygen evolution and Pt/SrTiO3 (Cr Ta doped) photocatalyst for hydrogen evolution, and a redox mediator, I /IO3 mimicking the Z scheme mechanism of the natural photosynthesis. The quantum yield of this system was about 0.1% at 420.7nm. Both photocatalytic methods are the first examples for visible light water splitting system in the world.Copyright (c) 2003 by ASME
author_names: Hironori Arakawa

Zhi-gang Zou

Kazuhiro Sayama

Ryu Abe
title: Solar Hydrogen Production: Direct Water Splitting Into Hydrogen and Oxygen by New Photocatalysts Under Visible Light Irradiation
year: 2003

abstract: Abstract The research on a new series of solid photocatalysts with different crystal structures was reviewed. The first system is A2B2O7 pyrochlore crystal type: Bi2MNbO7 (M=Al, Ga, In and Y, rare earth, and Fe) which is cubic system and space group Fd3m. The second system is ABO4 stibotantalite crystal type: BiMO4 (M=Nb5+ Ta5+ in which both the triclinic system with space group P1 in the case of M=Ta and the orthorhombic system with space group Pnna in the case of M=Nb. The third system is ABO4 wolframite crystal type: InMO4 (M=Nb5+ Ta5+ which is monoclinic system and space group P2/a. Although these photocatalysts crystallize in the different crystal structure, they contain the same octahedral TaO6 and/or NbO6 in the different photocatalysts. The band structure of the photocatalysts is defined by Ta/Nb d level for a conduction band and O 2p level for a valence band. The band gaps of the photocatalysts were estimated to be between 2.7 and 2.4 eV. Metal doped InTaO4 photocatalysts were also investigated. Under visible light (l>420 nm) or ultra violet irradiation, the H2 and/or O2 evolutions were observed from pure water as well as aqueous CH3OH/H2O and AgNO3 solutions. The photocatalytic activity increases significantly by loading co catalysts such as Pt, RuO2 and NiOx on the surface of the photocatalysts. Finally, direct water splitting into H2 and O2 under visible light irradiation was firstly established using newly synthesized NiOx (partly oxidized nickel) promoted In0.9Ni0.1TaO4 photocatalyst.
author_names: Zhi-gang Zou

Hironori Arakawa
title: Direct water splitting into H2 and O2 under visible light irradiation with a new series of mixed oxide semiconductor photocatalysts
year: 2003

abstract: Abstract Green and efficient energy technologies are a key point where nanoscience could make a difference in the paradigm shift from fossil fuels to renewable sources. One attractive possibility is the utilization of solar energy to obtain electricity or chemical fuel based on the ability of semiconductor nanomaterials to function as photocatalysts promoting various oxidation and reduction reactions under sunlight. We report on a novel class of Bi based photocatalysts for hydrogen production via water splitting. A screening DFT investigation was performed on the Bi2(MO4)3 (M Cr, Mo, and W) systems. The Bi2(CrO4)3 system exhibits the smallest band gap energy, the highest dielectric constant, and the highest absorption in visible region among the other counterpart materials. Consequently, Bi2(CrO4)3 nanoparticles were synthesized via a simple one pot method at room temperature and characterized by XRD, XPS, DRS, FE SEM, HR TEM, and Raman spectroscopy. The as prepared yellow Bi2(CrO4)3 nanoparticles exhibited a direct band gap energy of 2.45 eV. The photoactivity of the as prepared Bi2(CrO4)3 nanoparticles was tested toward the photocatalytic hydrogen production, where reasonable rates of 522.44, 174.15, and 88.24 mmol/g/h were achieved under UV, AM 1.5, and visible irradiations, respectively in the absence of any hole scavengers. Those rates are higher than those reported for Bi based photocatalysts.
author_names: Mahmoud Hamza

Ayat N El-Shazly

Sarah A Tolba

Nageh K Allam
title: Novel Bi based photocatalysts with unprecedented visible light driven hydrogen production rate: Experimental and DFT insights
year: 2020

abstract: Developing new technology to utilize solar power as alternative energy is imperative to meet the challenge of fossil fuel consumption and consequently environmental contamination. Photocatalytic overall water splitting is regarded as an ideal reaction for realizing solar to chemical energy conversion. Up to date, many particle suspension systems have been studied on a laboratory scale with inorganic semiconductors including metal oxides, (oxy)nitrides, and oxysulfides under ultra violet (UV) light irradiation [1] However, the solar to hydrogen energy conversion efficiency (STH) offered by these efforts is far from the requirements of scale up industrialization since visible light photons are not efficiently used. When Wang et al. [2] firstly reported g C3N4 for water splitting in 2009, conjugated polymers were merging as a promising candidate due to their easily tunable electronic properties over the inorganic counterparts for better visible light response [3] Realizing overall water splitting using g C3N4 based materials is attractive but proved to be challenging. As a single component photocatalyst, constructing spatially separated oxidation and reduction centers has been demonstrated to achieve the overall water splitting [4] Besides, the incorporation of carbon dots (C dots) promoting the H2O2 decomposition, is also an effective way to reach the overall water splitting [5] Z scheme, mimicking the natural photosynthesis process, provides an effective route to enhance the charge separation by forming a heterojunction from two semiconductors. The matching energy diagram and the efficient charge transfer are critical factors for the photocatalytic system, which depends on the types of both semiconductors and their contact interface. Significant progress has been made by Shen's group [6] through constructing two dimensional/two dimensional (2D/2D) Z scheme heterostructures of the carbon nitride based polymers. In this work, ultrathin carbon nitride nanosheets (CNN) with different band structures by modulating the levels of boron dopants and nitrogen defects were prepared to act as H2and O2 evolving photocatalysts, respectively (Figure 1(a) Through electrostatic self assembly and p p stacking, the boron doped and nitrogen deficient carbon nitride 2D nanosheets (BDCNN) are effectively coupled together to achieve a g C3N4 based 2D/2D Zscheme heterostructure. It enables overall water splitting to be realized due to their ultrathin nanostructures, strong interfacial interaction, and staggered band alignment (Figure 1 (b d) With the help of Pt and Co(OH)2 cocatalysts, this gC3N4 based heterostructure achieved a STH of 1.16% standing at the highest level reported for polymer photocatalysts for overall water splitting (Figure 1(e) The superior performance is experimentally and theoretically evidenced to originate from the direct Z scheme charge transfer pathway with the band structures of both the H2and O2 evolving components well optimized, which endows this g C3N4 based heterostructure with excellent charge transfer efficiency for facilitating charge separation and enough driving forces for the water redox reactions to simultaneously produce O2 and H2. This work rationally combines
author_names: Xupeng Zong

Wenshuai Jiang

Zaicheng Sun
title: Efficient photocatalytic overall water splitting achieved with polymeric semiconductor based Z scheme heterostructures
venue: Science China Chemistry
year: 2021

abstract: Direct water splitting into H2 and O2 using photocatalysts by harnessing sunlight is very appealing to produce storable chemical fuels. Conjugated polymers, which have tunable molecular structures and optoelectronic properties, are promising alternatives to inorganic semiconductors for water splitting. Unfortunately, conjugated polymers that are able to efficiently split pure water under visible light (400 nm) via a four electron pathway have not been previously reported. This study demonstrates that 1,3 diyne linked conjugated microporous polymer nanosheets (CMPNs) prepared by oxidative coupling of terminal alkynes such as 1,3,5 tris (4 ethynylphenyl) benzene (TEPB) and 1,3,5 triethynylbenzene (TEB) can act as highly efficient photocatalysts for splitting pure water (pH 7) into stoichiometric amounts of H2 and O2 under visible light. The apparent quantum efficiencies at 420 nm are 10.3% and 7.6% for CMPNs synthesized from TEPB and TEB, respectively; the measured solar to hydrogen conversion efficiency using the full solar spectrum can reach 0.6% surpassing photosynthetic plants in converting solar energy to biomass (globally average 0.10% First principles calculations reveal that photocatalytic H2 and O2 evolution reactions are energetically feasible for CMPNs under visible light irradiation. The findings suggest that organic polymers hold great potential for stable and scalable solar fuel generation.
author_names: Li-xi Wang

Yangyang Wan

Yanjun Ding

Sikai Wu

Yongde Zhang

Xinlei Zhang

Guoqing Zhang

Yujie Xiong

Xiaojun Wu

Jinlong Yang

Hangxun Xu
title: Conjugated Microporous Polymer Nanosheets for Overall Water Splitting Using Visible Light.
venue: Advanced materials
year: 2017

abstract: Photocatalytic water splitting using semiconductor materials has attracted considerable interest due to its potential for clean production of H2 from water through the conversion of abundant solar energy into chemical energy. This article briefly analyzed the trend and progress in the research and development of visible light responsive photocatalysts for water splitting in the past few years. Particularly, metal sulfides and composite photocatalysts were discussed. This brief review article aims at facilitating a search of stable and efficient photocatalysts for water splitting, and revealing fundamental insight into the development of novel visible light adsorbing photocatalysts. Keyword: water splitting, visible light, hydrogen production, metal sulfide Hydrogen (H2) production using visible light photocatalyst for water splitting has attracted considerable attention due to the growing demand for environmentally friendly and sustainable energy sources. The number of journal articles on water splitting for H2 production dramatically increased over the past few years (Fig.1) highlighting the tremendous interests in photocatalytic water splitting as a means of producing renewable clean energy production with minimum carbon footprint. Since the early 1970s, intensive efforts have been directed toward research and development of various photocatalytic materials for water splitting for H2 production. Most traditional photocatalysts, such as TiO2 and ZnGa2O4, have relatively large band gaps and thus can capture only ultraviolet (UV) irradiation, which accounts for a small fraction of solar irradiation. To overcome this limitation, many types of visible light absorbing materials with narrower band gaps, such as mixed oxides, oxynitride, and metal sulfides, are developed as shown in Fig. 2. Until today, developing visible light photocatalysts remains the focus in this field. As shown in Fig. 1, the number of journal articles on visible light driven photocatalyst between 2006 and 2010 is almost 5 times the number of journal articles published between 1981 and 1985. It is also worth noting that before 2000, the publications on water splitting under UV irradiation outnumbered those under visible light. By contrast, after 2000, much more attention is being directed toward water splitting under visible light, especially in the past five years. Moreover, the number of journal articles on UV driven water splitting has declined over that past 5 years. This article compared the quantum yield (QY) and H2 productivity in different novel visible light adsorbing photocatalytic systems that were developed in the past few years. This article also examined the colloidal stability or durability, quantum efficiency, and potential environmental impacts between different studies, which laid groundwork toward developing and designing new rationale Fig. 1. The number of journal articles on water splitting published with years. VIS: visible light. UV: ultraviolet. NSTI Nanotech 2013, www.nsti.org, ISBN 978 1 4822 0586 2 Vol. 3, 2013 584 visible light responsive photocatalysts. 1. Visible light driven metal sulfide photocatalyst for water splitting Metal sulfides are attractive materials as candidates of visible light driven photocatalysts due to the narrow band gaps and negative valence band potentials. Despite the excellent visible light photocatalytic activity, they often exhibit poor photostability and undergo photocorrosion with prolonged light illumination. Yet the photocorrosion can be suppressed in the presence of sacrificial reagents. Many metal sulfide photocatalysts have been successful for H2 evolution in the presence of sacrificial reagents as demonstrated in Table 1. For instance, CdS is one of the most popular photocatalysts, 4 because of its appropriate band gap (2.4eV) and electronic structures (e.g. the conduction band is 0.9 eV in reference to NHE at PH=7, the valence band is +1.5 eV in reference to NHE at PH=7) Different photocatalysts led to dramatically different QYs for different systems (Table 1) In addition, it is actually challenging to quantitatively compare the H2 production efficiency and productivity due to the lack of a common measure or indicator. So, H2 productivity expressed with different units (i.e. mmol/h, mmol/mg/h, and mmol/m/h) were proposed and calculated in Table 1. Due to the availability of data or experimental details in the reference articles, we were able to obtain some of the H2 productivity quantities, which appeared to vary significantly with photocatalytic systems. Yan et al. reported that a quantum yield of 93% at 420 nm using the Pt PdS/CdS photocatalyst in the presence of the sacrificial reagent of Na2S and Na2SO3 which is the highest photocatalytic activity so far. Accordingly, its H2 productivity seems to be the highest. However, Graphene CdS and CdSeZnS/Zr/Ti/phosphate, if evaluated by the H2 production rate per unit photocatalyst mass, would apparently yield much greater H2 than Pt PdS/CdS. Thus, it is important develop holistic evaluation methods to access the H2 productivity for different photocatalytic systems. 2. Water splitting for H2 production using composite photocatalysts Clearly, efficient photocatalytic water splitting systems require stable photocatalysts that have photocatalytic activity with repeated consecutive use. Most recently, many efforts have focused on the design of novel semiconductor materials and the optimization of chemical composition and microstructures to increase the photostability and quantum yield. For example, multicomponent sulfides, such as ZnIn2S4, 6 and (CuAg)xIn2xZn2(1 2x)S2 7, 8 have been studied as a new class of visible light driven photocatalysts for water splitting and H2 production. Zhang et al. recently developed a visible light responsive photocatalyst (Ru/(CuAg)0.15In0.3Zn1.4S2) and successfully achieved H2 evolution in the presence of KI as the sacrificial reagent. The study also examined the kinetics of photocatalytic generation of H2, stability and reusability of the catalyst over multiple cycles of H2 production and catalyst regeneration, which is not commonly reported elsewhere. The examination of stability and longevity of photocatalytic H2 production is important and necessary to quantitatively compare the actual H2 productivity from different photocatalytic systems. The photocatalyst reported by Zhang et al was well crystallized particles (30 50 nm in diameter) with high photocatalytic activity and broad visible light absorbance (from 400 nm up to 650 nm) The highest H2 production rate was approximately 190 6.5 mmol*h at the initial pH of 4 Fig. 2. The number of journal articles on different popular visible light responsive photocatalysts published from 2007 to 2012. NSTI Nanotech 2013, www.nsti.org, ISBN 978 1 4822 0586 2 Vol. 3, 2013 585 and 0.2 M KI as electron donor. The highest QY (QY under the wavelength of 420+ 5 nm) was 4.6 0.3% Although this QY does not seem to be stunning and even lower than those of some similar catalysts, such as Pt/CdS (QY 24% and (CuAg)0.15In0.3Zn1.4S2 (QY 7% the catalyst exhibited relatively good colloidal stability and was able to capture a wide spectrum of the solar irradiation (400 650 nm) Most importantly, this article provided systematic investigations on the longevity of the photocatalyst with consecutive reaction cycles. The study monitored the particle size distribution and metal ion release during the photocatalytic H2 production, which help understand why the H2 production rate decreased from 190 to 120 mmol*h with over different reaction cycles. It was experimentally observed that the photocatalyst particles underwent pronounced aggregation, which led to the increase in particle size; and a significant release of metal ions was observed during H2 production, which led to a loss of the catalyst mass and potential changes in the photocatalytic activity. Consequently, these processes may result in the decrease of photocatalytic activity and stability. 3. Conclusion Solar water splitting for H2 production is important to obtain clean energy in the future. Nowadays, there are many photocatalysts have been developed, and the focus is largely on the novel material synthesis and improvement of photocatalytic activity. In the future, it is necessary to take the stability and reusability of photocatalysts into consideration. In addition, applications of photocatalyst materials made of earth abundant elements would be more attractive and critical for energy sustainability. Table 1. Comparison of hydrogen evolution with different visible light responsive photocatalysts Catalyst Light source QY H2 Productivity Ref. mmol/h mmol/mg/h mmol/m/h Pt/CdS/TiO2 N.A. 20 54 0.68 N.A. 1 Pt PdS/CdS =420 nm 93 8770 29.23 N.A. 2 Pt/[In(OH)ySz]:Zn =420 nm 0.59 67 0.22 N.A. 12 PPy/CdS =430 nm N.A. 110 0.73 N.A. 13 Graphene CdS 420 nm 22.5 1120 556 N.A. 14 CdSeZnS/Zr/Ti/phosphate 420 nm 9.6 714 35.71 N.A. 15 CdS/TiO2 420 nm 43.4 402 N.A. N.A. 16 (Cd0.8Zn0.2)S =420 nm N.A. 302 3.02 N.A. 17
author_names: Yongsheng Chen

John C Crittenden

J Huang

Daisuke Minakata

Peng Wang

Guangshan Zhang

Wen Zhang
title: Water Splitting for H2 Production using Visible light responsive Photocatalysts
year: 2013

abstract: 57 Water splitting using a photocatalyst for direct solar hydrogen production from sunlight and water, has been regarded as an important approach to artificial photosynthesis.1,2 Solar hydrogen, which is the simplest solar fuel, can then be converted to various energy carriers such as organic hydrides, methanol, methane, and ammonia for transportation and storage. Thus, energy systems based on solar hydrogen can lead to a stable, secure, and ecologically friendly society. Although solar fuel production using electricity from photovoltaic cells and concentrated solar thermal power is an existing technology, direct synthesis of solar fuels by artificial photosynthesis has more scalability in terms of system cost. To split water into hydrogen and oxygen, 1.23 V of energy is required, corresponding to a 2 electron reaction. An energy of 1.23 V is equivalent to a photon energy of 1000 nm, so that the visible light (400 800 nm in wavelength) that represents half of the solar energy spectrum can be thermodynamically used for water splitting. The challenge is to obtain an efficient photocatalyst that has an absorption edge in longer wavelength and the ability to split water. Highly efficient oxide photocatalysts, such as La doped NaTaO3, and Zn doped Ga2O3, have been reported with quantum efficiencies of over 50%.3 5 However, these oxides only absorb ultraviolet (UV) light with wavelengths shorter than 300 nm. In the solar spectrum at the earth's surface, such short UV light is not present, so that these oxides cannot operate efficiently under solar irradiation. Most oxides have band gaps wider than the UV energy because of the deeper O 2p potential of the valence band. The valence band of nitrides is composed of the shallower N 2p potential, and thus their band gaps are generally narrower than those of oxides. For photocatalytic water splitting, photoexcited electrons in the conduction band reduce water to evolve hydrogen, and photogenerated holes in the valence band oxidize water to evolve oxygen. Therefore, the potential of the conduction band should be shallower than the reversible hydrogen potential and the potential of the valence band should be deeper than the reversible oxygen potential. In this article, the properties of oxynitride and nitride photocatalysts for water splitting are described. Surface modification of semiconductor photocatalyst particles with hydrogenor oxygen evolving cocatalysts is an indispensable technique in the study of photocatalytic water splitting. In fact, hydrogen evolution cocatalysts are required Photocatalytic Water Splitting Using Oxynitride and Nitride Semiconductor Powders for Production of Solar Hydrogen
author_names: Jun Kubota

Kazunari Domen
title: Photocatalytic Water Splitting Using Oxynitride and Nitride Semiconductor Powders for Production of Solar Hydrogen
year: 2013

abstract: The design, synthesis, and photoelectrochemical characterization of Co3 (PO4 )2 a hydrogen evolving catalyst modified with reduced graphene oxide (RGO) is reported. The 3 D flowerlike Co3 (PO4 )2 heterojunction system, consisting of 3 D flowerlike Co3 (PO4 )2 and RGO sheets, was synthesized by a one pot in situ photoassisted method under visible light irradiation, which was achieved without the addition of surfactant or a structure directing reagent. For the first time, Co3 (PO4 )2 is demonstrated to act as a hydrogen evolving catalyst rather than being used as an oxygen evolving photoanode. In particular, 3 D flowerlike Co3 (PO4 )2 anchored to RGO nanosheets is shown to possess dramatically improved photocatalytic activity. This enhanced photoactivity is mainly due to the staggered type II heterojunction system, in which photoinduced electrons from 3 D flowerlike Co3 (PO4 )2 transfer to the RGO sheets and result in decreased charge recombination, as evidenced by photoluminescence spectroscopy. The band gap of Co3 (PO4 )2 was calculated to be 2.35 eV by the Kubelka Munk method. Again, the Co3 (PO4 )2 semiconductor displays n type behavior, as observed from Mott Schottky measurements. These RGO Co3 (PO4 )2 conjugates are active in the visible range of solar light for water splitting and textile dye degradation, and can be used towards the development of greener and cheaper photocatalysts by exploiting solar light.
author_names: Alaka Samal

Smrutirekha Swain

Biswarup Satpati

Dipti P Das

Barada Kanta Mishra
title: 3 D Co3 (PO4 )2 Reduced Graphene Oxide Flowers for Photocatalytic Water Splitting: A Type II Staggered Heterojunction System.
venue: ChemSusChem
year: 2016