Hydrogen production from water splitting of real-time industry effluent using novel photocatalyst

The simultaneous degradation of real-time industrial effluent and hydrogen production was carried out in this study, taking into account the global clean energy demand. A novel photocatalyst based on a metal–organic framework and spindle-shaped titanium dioxide nanoparticles was synthesized to perform photocatalytic water splitting reactions. The resulting composite (MIL-53@TiO_2, MIL: Matériaux de l′Institut Lavoisier) was characterized by standard analytical methods. The photocatalytically active MIL-53@TiO₂ composite produced hydrogen without using any sacrificial agents. The hydrogen production was observed to be 0.26 mmol in the presence of TiO₂ which increased to 7.9 mmol in the presence of MIL-53@TiO₂ composite after 180 min of irradiation. The corresponding hydrogen evolution rate was 26.33 mmol h^-1g^?1, which was observed 30 times higher than the pristine materials. The remarkable photoactivity was due the superior charge separation property and less recombination of the charge carrier pair in the MIL-53@TiO₂ composite. Furthermore, the photocatalyst exhibited excellent reusability for hydrogen production up to 4 cycles. The results shown in the present work may be extended for large-scale applications.     

RGO nanosheets coupled NaNbO3 nanorods based nanocomposite for enhanced photocatalytic and photoelectrochemical water splitting activity

In this present work, reduced graphene oxide (RGO) coupled with hydrothermally grown sodium niobate nanorods (NaNbO₃-NRs) have been successfully synthesized. The photocatalytic performance of RGO/NaNbO₃-NRs photocatalyst demonstrated faster photodegradation of organic methylene blue (MB) dye than bare NaNbO₃-NRs. A ∼6 fold enhancement in the photocatalytic activity of RGO/NaNbO₃-NRs nanocomposite than that of NaNbO₃-NRs has been demonstrated towards the degradation of MB dye under similar light illumination. Furthermore, the potentiality of the fabricated NaNbO₃-NRs and RGO/NaNbO₃-NRs nanocomposite photoanodes have been investigated for photoelectrochemical (PEC) water splitting. The fabricated RGO/NaNbO₃-NRs nanocomposite photoanode showed ∼4 times higher photocurrent density than the NaNbO₃-NRs photoanode. The electrochemical impedance spectroscopy (EIS) and Mott-Schottky (MS) measurements demonstrated that coupling of RGO nanosheets in the RGO/NaNbO₃-NRs nanocomposite reduced the charge transfer resistance (R_ct) at the photoanode/electrolyte interface, increased the donor density (N_d), and reduced flat band potential (V_fb) of the RGO/NaNbO₃-NRs, thus significantly improving the PEC performance of the RGO/NaNbO₃-NRs nanocomposite. The enhancement in the PEC measurements of RGO/NaNbO₃-NRs nanocomposite is attributed to the extended absorption of the visible portion of the solar spectra and increased mobility of the photogenerated charge transport in the RGO nanosheets, which improve the separation efficiency and reduce the recombination process. The possible charge transfer mechanism has been proposed responsible for the enhanced photocatalytic and PEC water splitting performance.     

Visible light active ZnIn2S4/g-C3N4 heterostructure nanocomposite photoelectrode for efficient photoelectrochemical water splitting activity

Hexagonal zinc indium sulfide coupled g-C₃N₄ (H-ZnIn₂S₄/g-C₃N₄) nanocomposites were synthesized using chemisorption method and its performance towards photoelectrochemical water splitting activity was studied. The H-ZnIn₂S₄/g-C₃N₄ (H-ZIS/CN) nanocomposites exhibited ∼ 1.9 times enhanced photoelectrochemical performance as compared to the H-ZnIn₂S₄. The enhancement in the PEC water splitting activity of H-ZIS/CN nanocomposite is ascribed to the formation of type-II heterojunction which resulted in improved separation of photogenerated charge carriers and faster transfer of charges at the photoelectrode/electrolyte interface. The electrochemical impedance study and Mott-Schottky supported these results. Moreover, during photoelectrochemical reactions, H-ZIS/CN nanocomposites showed tremendous stability under visible light. A potential mechanism of the enhanced photoelectrochemical activity of H-ZIS/CN nanocomposites was proposed and endorsed by the PEC results. This study demonstrates that establishing a heterostructure system by coupling a ternary chalcogenide semiconductor with a conducting polymer is an effective strategy for PEC water splitting applications.     

Recent progress in oxynitride photocatalysts for visible-light-driven water splitting

Abstract

Photocatalytic water splitting into hydrogen and oxygen is a method to directly convert light energy into storable chemical energy, and has received considerable attention for use in large-scale solar energy utilization. Particulate semiconductors are generally used as photocatalysts, and semiconductor properties such as bandgap, band positions, and photocarrier mobility can heavily impact photocatalytic performance. The design of active photocatalysts has been performed with the consideration of such semiconductor properties. Photocatalysts have a catalytic aspect in addition to a semiconductor one. The ability to control surface redox reactions in order to efficiently produce targeted reactants is also important for photocatalysts. Over the past few decades, various photocatalysts for water splitting have been developed, and a recent main concern has been the development of visible-light sensitive photocatalysts for water splitting. This review introduces the study of water-splitting photocatalysts, with a focus on recent progress in visible-light induced overall water splitting on oxynitride photocatalysts. Various strategies for designing efficient photocatalysts for water splitting are also discussed herein.     

Recent progress in oxynitride photocatalysts for visible-light-driven water splitting

Photocatalytic water splitting into hydrogen and oxygen is a method to directly convert light energy into storable chemical energy, and has received considerable attention for use in large-scale solar energy utilization. Particulate semiconductors are generally used as photocatalysts, and semiconductor properties such as bandgap, band positions, and photocarrier mobility can heavily impact photocatalytic performance. The design of active photocatalysts has been performed with the consideration of such semiconductor properties. Photocatalysts have a catalytic aspect in addition to a semiconductor one. The ability to control surface redox reactions in order to efficiently produce targeted reactants is also important for photocatalysts. Over the past few decades, various photocatalysts for water splitting have been developed, and a recent main concern has been the development of visible-light sensitive photocatalysts for water splitting. This review introduces the study of water-splitting photocatalysts, with a focus on recent progress in visible-light induced overall water splitting on oxynitride photocatalysts. Various strategies for designing efficient photocatalysts for water splitting are also discussed herein.     

Bi4TaO8Cl/Graphene nanocomposite for photocatalytic water splitting

Sillen-Aurivillius structures like Bi₄NbO₈Cl, Bi₄TaO₈Cl, and Bi₄TaO₈Br have been expected as efficient visible light active photocatalysts thanks to their narrow band gaps less than 2.5 eV and suitable negative conduction band potential for hydrogen production reaction, 0.0 V vs NHE. However, despite their excellent potential the photocatalytic hydrogen generation efficiency of them under visible light has remained low. The low activity is usually attributed to the shallow defect levels near the conduction band, causing fast recombinations of photoexcited electrons and holes. In this study, a nanocomposite of Bi₄TaO₈Cl and graphene is proposed for overcoming this issue. The excellent electron conductivity and abundant delocalized electrons from the conjugated sp²-bonded carbon networks in graphene can facilitate the transfer of electrons from Bi₄TaO₈Cl conduction band and increase the photocatalytic efficiency. Bi₄TaO₈Cl/graphene nanocomposite was successfully prepared by a hydrothermal method, and photocatalytic activity enhanced both under UV and visible light.     

Self-supporting amorphous nanoporous NiFeCoP electrocatalyst for efficient overall water splitting

The design of cost-effective and earth-abundant bifunctional electrocatalysts for highly efficient oxy-gen evolution reaction(OER)and hydrogen evolution reaction(HER)is important for water splitting as an advanced renewable energy transformation system.In this work,the self-supporting amorphous NiFeCoP catalyst with nanoporous structure via a facile electrochemical dealloying method is reported.Benefiting from the bicontinuous nanostructure,disordered atomic arrangement,abundant active sites and synergic effect of various transition metals,the as-prepared nanoporous NiFeCoP(np-NiFeCoP)cat-alyst exhibits good electrocatalytic activity,which achieves the current densities of 10 mA cm-2 at low overpotentials of 244 mV and 105 mV for OER and HER in 1.0 M KOH,respectively.In addition,the bifunc-tional electrocatalyst also shows outstanding and durable electrocatalytic activity in water splitting with a small voltage of 1.62 V to drive a current density of 10 mA cm-2 in a two-electrode electrolyzer system.The present work would provide a feasible strategy to explore the efficient and low-cost bifunctional electrocatalysts toward overall water splitting.     

SrTiO3-CaCr0.5Nb0.5O3 solid solutions as p-type photocatalysts for Z-scheme water splitting under visible light illumination

P-type semiconductivity has been observed in solid solution series (SrTiO3)1-x(CaCr0.5Nb0.5O3)x (0.0 ≤x ≤ 0.15),which all adopt cubic symmetry and own intense absorption in the visible light region.These solid solutions are superior H2 evolution photocatalysts under visible light illumination (λ ≥400 nm).An AQE as high as 1.02 ％ at 420 ± 20 nm has been achieved at optimal composition(SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15 which significantly surpasses the parent compounds.Stoichiometric H2/O2 production under visible light illumination has been successfully realized using Z-scheme system containing (SrTiO3)0.85(CaCr0.5Nb0.5O3)0.15,WO3 and I-/IO3-redox couple.     

Hierarchical NiMoP2-Ni2P with amorphous interface as superior bifunctional electrocatalysts for overall water splitting

Producing highly efficient bifunctional catalyst for the generation of hydrogen and oxygen through overall water splitting is an emerging direction in electrocatalysis,Herein,a dandelion-like hierarchi-cal NiMoP2-Ni2P(nanowire/nanoparticle)heterostructure was synthesized for efficient electrochemical water splitting.The NiMoP2-Ni2P heterostructures grown on carbon cloth as a freestanding integrated electrode exhibited excellent oxygen evolution reaction(OER)activity and hydrogen evolution reaction(HER)activities with low overpotentials(258 mV and 53 mV to reach 10 mA cm-2 for the OER and HER,respectively),and small Tafel slope(45 mV dec-1 and 58 mV dec-1 for the OER and HER,respectively).Moreover,the NiMoP2-Ni2 P heterostructure can act as both anode and cathode catalysts for overall water splitting with low overall potential of 1.48 V at 10 mA cm-2.Density functional theory(DFT)combined with structural probes suggests that the amorphous heterogeneous interfaces play an essential role in enhanced catalytic performance.     

Chemical vapor deposition of amorphous molybdenum sulphide on black phosphorus for photoelectrochemical water splitting

Non-precious metal electrocatalyst molybdenum sulphide(MoS) and black phosphorus(BP) are highly promising catalysts for H₂ evolution reaction(HER).However,BP is environmentally unstable and the basal planes of crystal MoS₂ are inactive toward HER.Herein,amorphous molybdenum sulphide(MoSx)directly on BP/BiVO4 film dramatically improves the performance of photoelectrochemical water splitting compared with pure BiVO4.Additionally,we demonstrate that a BP layer,inserted between the MoSx and BiVO4,can enhance the photoelectrochemical performance and improve the stability of the electrodes.Finally,MoS_x/B P/BVO electrode shows the excellent current density of 2.1 mA/cm² at the potential of 1.2 V(vs Ag/AgCl),which is twice higher than that of pure BVO electrode.Our novel nanostructure materials will lead to a new class of non-precious metal photocatalysts for hydrogen production.     

高温堆的热利用--热化学循环制氢的研究

利用高温堆提供的900℃的高温热源，用碘－硫（IS）循环热化学水解的方法可得到没有二氧化碳释放的能源系统。介绍了IS循环的概念、IS循环实验室规模生产氢气的实验验证以及对IS循环闭合回路改进的研究。     

钽酸盐光催化分解水研究进展

钽酸盐光解水催化剂,因其特殊的晶体结构和能带结构而具有高的光解水活性。结合本课题组工作,论述了钽酸盐光解水催化剂的种类、结构特点、制备方法及发展趋势,以期为今后的光解水制氢研究提供参考依据。     

电纺碳基纤维材料电催化水分解制氢

电解水制氢是由阴极析氢反应(HER)和阳极析氧反应(OER)组成。由于HER和OER所需的过电位高,反应动力学迟缓,导致电解水槽电压远高于理论平衡电压,电能消耗严重。因此,探索高效、稳定的非贵金属基电催化剂具有重要的研究意义。利用静电纺丝技术构筑的纤维材料因其较大的比表面积、独特的化学结构、易于调节的组分以及快速的电子和物质传输性能而被广泛应用在能源转化与存储领域。基于此,综述了近几年电纺碳基纤维材料在电催化水分解制氢中的研究进展,重点关注了静电纺丝技术制备的纳米纤维电催化剂用于HER、OER以及作为双功能催化剂在全水分解中产生高催化性能的优势,并对电纺材料在电催化水分解中的应用特点及其未来可能面临的挑战和发展趋势进行了展望。     

Defect engineering of nanostructures: Insights into photoelectrochemical water splitting

Development of long-term and sustainable energy economy is one of the most significant technical challenges facing humanity. Photoelectrochemical (PEC) water splitting is regarded as the most attractive approach for conversion of solar energy to chemical energy, with H₂ and O₂ as the energy carriers. Defect engineering of photocatalytic materials has been proved effective in improving their performances in PEC water splitting process involving three basic steps, i.e., light absorption, charge transfer/separation, and surface catalytic reaction. In this paper, recent developments in using various techniques to introduce, characterize and regulate defects are summarized, based on which the important roles played by defects are highlighted in the development of high-performance defect engineered photoelectrodes for PEC water splitting application. Moreover, current challenges and future perspectives in the field of defect engineering of nanostructures for photoelectrodes are discussed.     

BiVO4的水热合成及其光催化分解水产氧性能研究

以无机盐为前体，采用表面活性剂为模板，水热法制备了具有较高含量的单斜晶系BiVO4．实验结果表明，随着水热温度的升高，产物中单斜晶系BiVO4的含量增大，其光催化分解水产氧的效果越好．讨论了制备的BiVO4在牺牲试剂Fe（NO3）3存在下的产氧效率及其与产物晶型的关系。在优化的实验条件下获得了较高的光催化分解水产氧效率。     

Ta3N5 photoanodes for water splitting prepared by sputtering

Ta₃N₅ thin-film photoelectrodes were prepared using a reactive sputtering technique, and their properties for photoelectrochemical water splitting under visible light were investigated. The crystal phases of the films were dependent on the sputtering conditions, such as the N₂/O₂ ratio of the sputtering atmosphere and the substrate temperature (T_s). Single-phase Ta₃N₅ films were obtained by sputtering at N₂/O₂ = 30 and T_s = 1013 K with post-annealing in an NH₃ flow. The Ta₃N₅ photoelectrodes had an anodic photoresponse in water photoelectrolysis, although the photocurrent rapidly decreased because of self-oxidation of the photoanode by photogenerated holes. However, modification of the NH₃-treated Ta₃N₅ films with IrO₂ promoted the oxidation of water and suppressed the self-oxidation of Ta₃N₅.     

A novel Z-scheme CeO2/g-C3N4 heterojunction photocatalyst for degradation of Bisphenol A and hydrogen evolution and insight of the photocatalysis mechanism

CeO2/g-C3N4 heterojunction photocatalyst had been successfully fabricated through a one-step in-situ pyrolysis formation of 3D hollow CeO2 mesoporous nanospheres and 2D g-C3N4 nanosheets together with simultaneous removal of carbon sphere templates after heat treatment.The sample shows high catalytic performances for photocatalytic hydrogen generation and photocatalytic oxidation of Bisphe-nol A(BPA)under visible light irradiation,and the catalytic degradation route of BPA was suggested by the degradation products determined by GC-MS.The enhancing catalytic activity was attributed to the effective interfacial charge migration and separation.Finally,it was proposed that the CeO2/g-C3N4 het-erojunction photocatalyst could follow a more appropriate Z-scheme charge transfer mechanism,which was confirmed by the analysis of experiment and theoretical calculation results.     

Dye-sensitized photocatalyst for effective water splitting catalyst

Abstract

Renewable hydrogen production is a sustainable method for the development of next-generation energy technologies. Utilising solar energy and photocatalysts to split water is an ideal method to produce hydrogen. In this review, the fundamental principles and recent progress of hydrogen production by artificial photosynthesis are reviewed, focusing on hydrogen production from photocatalytic water splitting using organic–inorganic composite-based photocatalysts.     

食品工业中的双极膜技术

双极膜是近年来国际上研究比较活跃的一种新型膜．基于双极膜的水解离技术乒逐渐成为一种通用的目标单元操作，可用于多种工业过程，如化工生产、湿法冶金、环境保护和资源回收等领域，并大大地改变了这些领域的面貌．本文针对食品工业领域，介绍了双极膜在食品化工中的应用和研究现状．