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Solar water splitting

Ning Wang, Guang Yang, Haixu Wang, Rong Sun, Ching-Ping Wong
Photocatalysts are essential to promote the highly efficient applications of solar energy in water splitting and/or the degradation of organic contaminations. Especially, the visible light-responsive photocatalysts could benefit with the cost-effective splitting or degradation due to the unlimited sunlight and the absence of expensive light emitter. In the photocatalysts, the charge transfer rates as well as the hole-electron recombination rate are two critical factors that determine the photocatalytic activity, which could also be affected by the dimension, defects, doping and morphologies controlled by the synthesis methods...
2018: Frontiers in Chemistry
Robert Godin, Takashi Hisatomi, Kazunari Domen, James R Durrant
A persistent challenge for the widespread deployment of solar fuels is the development of high efficiency photocatalysts combined with a low-cost preparation and implementation route. Since its discovery in 2005, GaN:ZnO solid solution has been a benchmark overall water splitting photocatalyst. Notably, GaN:ZnO functionalised with an appropriate proton reduction cocatalyst is one of the few particulate photocatalyst systems that can generate hydrogen and oxygen directly from water using visible light. However, the reasons underlying the remarkable visible light activity of GaN:ZnO are not well understood and photophysical studies of GaN:ZnO have been limited to date...
October 14, 2018: Chemical Science
Rongjuan Feng, Wanying Lei, Gang Liu, Minghua Liu
Direct utilization of the full spectrum of renewable solar light, in particular the visible- and near-infrared (NIR) portions, is currently receiving a great deal of attention in solar-to-chemical energy conversion-a clean, economically, and environmentally sustainable process. Black phosphorus (BP), a newly emerging class of ultrathin 2D nanomaterials rediscovered in early 2014, fulfills this purpose due to its unique properties like high charge-carrier mobility and tunable direct-bandgap. To this end, the rational combinations of BP in the form of few-layer nanosheets or ultrasmall quantum dots with a range of organic and inorganic nanomaterials offer more versatile and robust hybrids and nanocomposites that are functional in solar fuel production and environmental remediation...
October 15, 2018: Advanced Materials
Shiman He, Yuying Meng, Qili Wu, Jingling Yang, Senchuan Huang, Xiaohui Li, Shengfu Tong, Tewodros Asefa, Mingmei Wu
Owing to its excellent chemical stability and low cost, titanium dioxide (TiO2) has been widely studied as a photoanode for photoelectrochemical (PEC) water splitting. However, TiO2's practical applications in solar energy-to-synthetic fuel conversion processes have been constrained by its inherently poor ability to transport photogenerated electrons and holes. In this paper, we report Ta-doped porous TiO2 nanorod arrays on Ta foil (Ta-PTNA) that do not possess this issue and that can thus efficiently photoelectrocatalyze water oxidation, helping the production of H2 (a clean fuel) from water at the expense of solar light...
October 11, 2018: Nanoscale
Shunichi Fukuzumi, Yong-Min Lee, Wonwoo Nam
The structure and function of photosynthetic reaction centers (PRCs) have been modeled by designing and synthesizing electron donor-acceptor ensembles including electron mediators, which can mimic multi-step photoinduced charge separation occurring in PRCs to obtain long-lived charge-separated states. PRCs in photosystem I (PSI) or/and photosystem II (PSII) have been utilized as components of solar cells to convert solar energy to electric energy. Biohybrid photoelectrochemical cells composed of PSII have also been developed for solar-driven water splitting into H2 and O2 Such a strategy to bridge natural photosynthesis with artificial photosynthesis is discussed in this minireview...
October 8, 2018: Biochemical Society Transactions
Yejun Xiao, Yu Qi, Xiuli Wang, Xiaoyu Wang, Fuxiang Zhang, Can Li
The development of new metal-organic frameworks (MOFs) with dual functions of both water reduction and oxidation under visible-light irradiation is highly desirable for promising solar water splitting, but is not yet reported. Herein, a cadmium-based MOF (denoted as "Cd-TBAPy") single crystal with a 2D layered framework by employing 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H4 TBAPy) as an organic linker is reported, which exhibits good visible-light absorption with edge of ≈600 nm. The Mott-Schottky (M-S) measurement and UV-vis analysis integrally reveal that the Cd-TBAPy is an n-type semiconductor with a bandgap of ≈2...
September 17, 2018: Advanced Materials
Hai-Cai Huang, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma
The pristine BaTiO3 has been experimentally confirmed to catalyze hydrogen production from water splitting, but the reaction cannot be driven by the visible light because of the wide energy band gap of BaTiO3 . To understand the feasibility of the reaction driven by the visible light of the strongest part of the solar energy, we have investigated the effect of different concentrations of oxygen group element dopants on the electronic and optical properties of BaTiO3 by using first-principles density functional theory calculations with meta-GGA + MBJ potential...
September 27, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Chi Zhang, Yi Li, Danmeng Shuai, Yun Shen, Wei Xiong, Linqiong Wang
Microbial contamination in drinking water is of great concern around the world because of high pathogenic risks to humans. Semiconductor photocatalysis has aroused an increasing interest as a promising environmental remediation technology for water disinfection and microbial control. Among various photocatalysts, graphitic carbon nitride (g-C3 N4 ), as a fascinating two-dimensional conjugated polymer consisting of low-cost, earth-abundant elements, has drawn broad attention as a robust, metal-free, and visible-light-active material in the fields of both environmental remediation and solar energy conversion...
September 24, 2018: Chemosphere
Markku Hannula, Harri Ali-Löytty, Kimmo Lahtonen, Essi Sarlin, Jesse Saari, Mika Valden
Amorphous titanium dioxide (a-TiO2 ) combined with an electrocatalyst has shown to be a promising coating for stabilizing traditional semiconductor materials used in artificial photosynthesis for efficient photoelectrochemical solar-to-fuel energy conversion. In this study we report a detailed analysis of two methods of modifying an undoped thin film of atomic layer deposited (ALD) a-TiO2 without an electrocatalyst to affect its performance in water splitting reaction as a protective photoelectrode coating...
February 27, 2018: Chemistry of Materials: a Publication of the American Chemical Society
Tayyebeh Soltani, Ahmad Tayyebi, Byeong-Kyu Lee
Among the various synthetic techniques, the sonochemical method has emerged as an interesting method for fabricating different photocatalysis materials with unique photoelectrochemical (PEC) properties. In comparison with the classical method without sonication, this study examines the promoting effect of ultrasonic irradiation during the synthesis of tungsten oxide (WO3 ) nanoplates within short reaction times (15 and 30 min). The shorter ultrasonic reaction time (15 min) was sufficient for the uniform growth of thin and compact layers of WO3 nanoparticles (NPs) on the surface of a tungsten foil...
September 25, 2018: Ultrasonics Sonochemistry
Kiwon Kim, Jun Hyuk Moon
A photoanode capable of high-efficiency water oxidation at low bias potential is essential for its practical application for photocathode-coupled tandem systems. To address this issue, a photoanode with low turn-on voltage for water oxidation and high charge separation efficiency at low bias potential is essential. In this study, we demonstrate the photoanode of the BiVO4 /ZnO three-dimensional (3D) bicontinuous (BC) structure. ZnO has a relatively cathodic flat-band potential, which leads to low turn-on potential; the BiVO4 /ZnO 3D BC photoanode shows an onset potential of 0...
October 10, 2018: ACS Applied Materials & Interfaces
Hannes Hempel, Charles J Hages, Rainer Eichberger, Ingrid Repins, Thomas Unold
The mobilities of electrons and holes determine the applicability of any semiconductor, but their individual measurement remains a major challenge. Here, we show that time-resolved terahertz spectroscopy (TRTS) can distinguish the mobilities of minority and majority charge carriers independently of the doping-type and without electrical contacts. To this end, we combine the well-established determination of the sum of electron and hole mobilities from photo-induced THz absorption spectra with mobility-dependent ambipolar modeling of TRTS transients...
September 27, 2018: Scientific Reports
Teresa J Bandosz, Conchi O Ania
Even though, owing to the complexity of nanoporous carbons' structure and chemistry, the origin of their photoactivity is not yet fully understood, the recent works addressed here clearly show the ability of these materials to absorb light and convert the photogenerated charge carriers into chemical reactions. In many aspects, nanoporous carbons are similar to graphene; their pores are built of distorted graphene layers and defects that arise from their amorphicity and reactivity. As in graphene, the photoactivity of nanoporous carbons is linked to their semiconducting, optical, and electronic properties, defined by the composition and structural defects in the distorted graphene layers that facilitate the exciton splitting and charge separation, minimizing surface recombination...
September 2018: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Helge Stein, Sönke Müller, Klaus Schwarzburg, Dennis Friedrich, Alfred Ludwig, Rainer Eichberger
The effect of compositional variation on charge carrier lifetimes of Cr1 Fe0.84 Al0.16 O3 , a promising material for solar water splitting recently identified using combinatorial materials science, is explored using ultrafast time-resolved optical reflectance. The transient signal can be described by a biexponential decay where the shorter time constant varies over one order of magnitude with changing Cr content while the longer one stays constant. Intrinsic performance limitations such as a low charge carrier mobility on the order of 10-3 cm2 /(Vs) are identified...
September 24, 2018: ACS Applied Materials & Interfaces
Mengyuan Zhang, Rajini P Antony, Sing Yang Chiam, Fatwa Firdaus Abdi, Lydia Helena Wong
Solar water oxidation is considered as one of the most promising methods to utilize solar energy efficiently, and bismuth vanadate (BiVO4) is a potential photoanode. Catalyst loading on BiVO4 is often used to tackle the limitations of charge recombination and sluggish kinetics. In this study, amorphous nickel oxide (NiOx) is loaded on BiVO4 by photochemical metal organic deposition method. The resulting NiOx/Mo:BiVO4 photoanodes demonstrates a 2-fold improvement of photocurrent density of 2.44 mA cm-2 at 1...
September 24, 2018: ChemSusChem
Baowen Zhou, Xianghua Kong, Srinivas Vanka, Sheng Chu, Pegah Ghamari, Yichen Wang, Nick Pant, Ishiang Shih, Hong Guo, Zetian Mi
The combination of earth-abundant catalysts and semiconductors, for example, molybdenum sulfides and planar silicon, presents a promising avenue for the large-scale conversion of solar energy to hydrogen. The inferior interface between molybdenum sulfides and planar silicon, however, severely suppresses charge carrier extraction, thus limiting the performance. Here, we demonstrate that defect-free gallium nitride nanowire is ideally used as a linker of planar silicon and molybdenum sulfides to produce a high-quality shell-core heterostructure...
September 21, 2018: Nature Communications
Cen-Feng Fu, Jiuyu Sun, Qiquan Luo, Xingxing Li, Wei Hu, Jinlong Yang
Two-dimensional (2D) materials with the vertical intrinsic electric fields show great promise in inhibiting the recombination of photogenerated carriers and widening light absorption region for the photocatalytic applications. For the first time, we investigated the potential feasibility of the experimentally attainable 2D M2 X3 (M = Al, Ga, In; X = S, Se, Te) family featuring out-of-plane ferroelectricity used in photocatalytic water splitting. By using first-principles calculations, all the nine members of 2D M2 X3 are verified to be available photocatalysts for overall water splitting...
September 24, 2018: Nano Letters
Lodvert Tchibota Poaty, Kanchan Ulman, Nicola Seriani, Bernard M'Passi-Mabiala, Ralph Gebauer
We use density functional theory-based calculations to study structural, electronic, and magnetic properties of two key reaction intermediates on a hematite, [Formula: see text]-Fe2 O3 , photoanode during the solar-driven water splitting reaction. Both intermediates contain an oxygen atom bonded to a surface iron atom. In one case, the adsorbed oxygen also forms a peroxo bond with a lattice oxygen from hematite; in the second case no such bond is formed. Both configurations are energetically equivalent and are related to the overpotential-determining step in the oxygen evolution reaction...
September 18, 2018: Journal of Molecular Modeling
Srinivas Vanka, Elisabetta Arca, Shaobo Cheng, Kai Sun, Gianluigi A Botton, Glenn Teeter, Zetian Mi
Photoelectrochemical water splitting is a clean and environmentally friendly method for solar hydrogen generation. Its practical application, however, has been limited by the poor stability of semiconductor photoelectrodes. In this work, we demonstrate the use of GaN nanostructures as a multifunctional protection layer for an otherwise unstable, low-performance photocathode. The direct integration of GaN nanostructures on n+ -p Si wafer not only protects Si surface from corrosion but also significantly reduces the charge carrier transfer resistance at the semiconductor/liquid junction, leading to long-term stability (>100 h) at a large current density (>35 mA/cm2 ) under 1 sun illumination...
September 20, 2018: Nano Letters
Junyan Cui, Can Li, Fuxiang Zhang
The rapid fossil-fuel consumption, severe environmental concerns, and growing energy demands call for the exploitation of environmentally friendly, recyclable new energy. Fuel-producing artificial system that directly converts solar energy into fuels by mimicking natural photosynthesis, is expected to achieve this goal. Among them, the conversion of solar energy to hydrogen energy through photocatalytic water splitting process over a particulate semiconductor is one of the most promising routes due to the advantages such as simplicity, cheapness and ease for large-scale production etc...
September 13, 2018: ChemSusChem
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