Electrolyte transfer separation of hollow fiber composite nanofiltration membrane

Using Donnan Steric Partitioning Model(DSPM),the data for the rejection of four salts having common co-ion(LiCl, NaCl,KCl,Na2SO4)were obtained and they show the characters of the polyethersulfone(PES)nanofiltration(NF)membrane in terms of three parameters:an effective pore radius(rp),the ratio of effective thickness over porosity(λ/Ak)and an effective charge density(X).Good agreement between experimental data and prediction data using the three parameters mentioned above was obtained.A theoretical model was developed to predict the transport performance of electrolyte through the hollow fiber composite NF membrane.The model prediction is in good agreement with experimental results based on the method by modern numerical solution.

Modulating charge separation and transfer for high-performance photoelectrodes via built-in electric field

Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer,thereby improving photoelectrochemical performance.Recently,considerable efforts have been devoted to this endeavor.This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms,focusing on the modulation of built-in electric fields in terms of depth and orderliness.First,mechanisms and tuning strategies for built-in electric fields are explored.Then,the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth.Finally,current strategies for constructing bulk built-in electric fields in photoelectrodes are explored,and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.

Long-range electron synergy over Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst in enhancing charge separation for photocatalytic hydrogen production

The development of novel single-atom catalysts with optimal electron configuration and economical noble-metal cocatalyst for efficient photocatalytic hydrogen production is of great importance,but still challenging.Herein,we fabricate Pt and Co single-atom sites successively on polymeric carbon nitride(CN).In this Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst,the noble-metal active sites are maximized,and the single-atomic Co_(1)N_4sites are tuned to Co_(1)N_3sites by photogenerated electrons arising from the introduced single-atomic Pt_(1)N_4sites.Mechanism studies and density functional theory(DFT)calculations reveal that the 3d orbitals of Co_(1)N_3single sites are filled with unpaired d-electrons,which lead to the improved visible-light response,carrier separation and charge migration for CN photocatalysts.Thereafter,the protons adsorption and activation are promoted.Taking this advantage of long-range electron synergy in bimetallic single atomic sites,the photocatalytic hydrogen evolution activity over Pt_(1)-Co_(1)/CN achieves 915.8 mmol g^(-1)Pt h^(-1),which is 19.8 times higher than Co_(1)/CN and 3.5 times higher to Pt_(1)/CN.While this electron-synergistic effect is not so efficient for Pt nanoclusters.These results demonstrate the synergistic effect at electron-level and provide electron-level guidance for the design of efficient photocatalysts.

Fast charge transfer kinetics in Sv-ZnIn_(2)S_(4)/Sb_(2)S_(3)S-scheme heterojunction photocatalyst for enhanced photocatalytic hydrogen evolution

Constructing a S-scheme heterojunction with tight interface contact and fast charge transfer is beneficial to improving the photocatalytic hydrogen evolution performance.Herein,a unique one-dimensional(1D)/two-dimensional(2D)S-scheme heterojunction containing 1D Sb_(2)S_(3) nanorods and 2D ZnIn_(2)S_(4) with affluent sulfur vacancies(denoted as Sv-ZnIn_(2)S_(4)@Sb_(2)S_(3)) was designed.The introduced sulfur vacancy can promote the effective adsorption of H+for the following interfacial hydrogen-evolution reaction.Furthermore,the larger contact area and stronger electron interaction between Sb_(2)S_(3) and ZnIn_(2)S_(4) effectively inhibits the recombination of photo-generated electron–hole pairs and abridges the migration distance of charges.As a result,the optimal Sv-ZnIn_(2)S_(4)@Sb_(2)S_(3) sample achieves H_(2) evolution activity of 2741.3 mol·h^(−1)·g^(−1),which is 8.6 times that of pristine ZnIn_(2)S_(4) and 3.0 times that of the Sv-ZnIn_(2)S_(4) samples.Based on the experimental result,the photo-reactivity S-scheme mechanism of hydrogen evolution from water splitting with Sv-ZnIn_(2)S_(4)@Sb_(2)S_(3) is proposed.This work provides an effective method for developing S-scheme heterojunction composites of transition metal sulfide with high hydrogen evolution performance.

Synthesis of TiO_2/g-C_3N_4 nanocomposites with phosphate–oxygen functional bridges for improved photocatalytic activity

One of the most general methods to enhance the separation of photogenerated carriers for g‐C3N4is to construct a suitable heterojunctional composite,according to the principle of matching energy levels.The interface contact in the fabricated nanocomposite greatly influences the charge transfer and separation so as to determine the final photocatalytic activities.However,the role of interface contact is often neglected,and is rarely reported to date.Hence,it is possible to further enhance the photocatalytic activity of g‐C3N4‐based nanocomposite by improving the interfacial connection.Herein,phosphate-oxygen(P-O)bridged TiO2/g‐C3N4nanocomposites were successfully synthesized using a simple wet chemical method,and the effects of the P-O functional bridges on the photogenerated charge separation and photocatalytic activity for pollutant degradation and CO2reduction were investigated.The photocatalytic activity of g‐C3N4was greatly improved upon coupling with an appropriate amount of nanocrystalline TiO2,especially with P-O bridged TiO2.Atmosphere‐controlled steady‐state surface photovoltage spectroscopy and photoluminescence spectroscopy analyses revealed clearly the enhancement of photogenerated charge separation of g‐C3N4upon coupling with the P-O bridged TiO2,resulting from the built P-O bridges between TiO2and g‐C3N4so as to promote effective transfer of excited electrons from g‐C3N4to TiO2.This enhancement was responsible for the improved photoactivity of the P-O bridged TiO2/g‐C3N4nanocomposite,which exhibited three‐time photocatalytic activity enhancement for2,4‐dichlorophenol degradation and CO2reduction compared with bare g‐C3N4.Furthermore,radical‐trapping experiments revealed that the·OH species formed as hole‐modulated direct intermediates dominated the photocatalytic degradation of2,4‐dichlorophenol.This work provides a feasible strategy for the design and synthesis of high‐performance g‐C3N4‐based nanocomposite photocatalysts for pollutant degradation and CO2reduction.

Enhanced photoelectrochemical water splitting using a cobalt-sulfide-decorated BiVO_(4) photoanode

Solar-driven water splitting is considered as a promising method to mitigate the energy crisis and various environmental issues.Bismuth vanadate(BiVO_(4))is photoanode material with tremendous potential for photoelectrochemical(PEC)water splitting.However,its PEC performance is severely hindered owing to poor surface charge transfer,surface recombination at the photoanode/electrolyte junction,and sluggish oxygen evolution reaction(OER)kinetics.In this regard,a novel solution was developed in this study to address these issues by decorating the surface of BiVO_(4)with cobalt sulfide,whose attractive features such as low cost,high conductivity,and rapid charge-transfer ability assisted in improving the PEC activity of the BiVO_(4)photoanode.The fabricated photoanode exhibited a significantly enhanced photocurrent density of 3.2 m A cm^(-2)under illumination at 1.23 V vs.a reversible hydrogen electrode,which is more than 2.5 times greater than that of pristine BiVO_(4).Moreover,the Co S/BiVO_(4)photoanode also exhibited considerable improvements in the charge injection yield(75.8%vs.36.7%for the bare BiVO_(4)film)and charge separation efficiency(79.8%vs.66.8%for the pristine BiVO_(4)film).These dramatic enhancements were primarily ascribed to rapid charge-transport kinetics and efficient reduction of the anodic overpotential for oxygen evolution enabled by the surface modification of BiVO_(4)by Co S.This study provides valuable suggestions for designing efficient photocatalysts via surface modification to improve the PEC performance.

Phase separations in graded-indium content InGaN/GaN multiple quantum wells and its function to high quantum efficiency

Phase separations have been studied for graded-indium content In_xGa_（1-x）N/GaN multiple quantum wells（MQWs） with different indium contents by means of photoluminescence（PL）,cathodeluminescence（CL） and time-resolved PL（TRPL） techniques.Besides the main emission peaks,all samples show another 2 peaks at the high and low energy parts of the main peaks in PL when excited at 10 K.CL images show a clear contrast for 3 samples,which indicates an increasing phase separation with increasing indium content.TRPL spectra at 15 K of the main emissions show an increasing delay of rising time with indium content,which means a carrier transferring from low indium content structures to high indium content structures.

An Inorganic-Organic Hybrid Polymer Cocatalyst for Photoelectrochemical Water Oxidation with Dual Functions of Accelerating Kinetics and Improving Charge Transfer

Oxygen evolution cocatalysts(OECs)play important roles in improving the efficiency of photocatalysts in solar water splitting.Inorganic–organic hybrid polymers(IOHPs),which have good electrolyte accessibility and evenly distributed active sites,are expected to be promising OECs.Here,a novel IOHP[Co(Bpn)_(2)(SCN)_(2)]n(1,Bpn=2,6-bis(4-pyridyl)-naphthalene,SCN=thiocyanate ion)exhibited a two-dimensional(2D)layer structure with(4,4)topology,was constructed by Bpn ligands connecting Co(II)ions,and was decorated on BiVO_(4) photoanodes for photoelectrochemical(PEC)water oxidation.The 1/BiVO_(4) hybrid electrode showed significantly negative onset potential and approximately 3.7 times higher photocurrent density at 1.23 V versus reversible hydrogen electrode(RHE)compared with the bare BiVO_(4).The mechanisms for the improved PEC efficiency were investigated and mainly ascribed to enhanced water oxidation kinetics and increased charge separation and transfer properties.This work provides a promising OEC candidate for PEC water oxidation and sheds light on the attractive application prospect of IOHPs for solar water splitting.

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO_(2) reduction: A review

Photocatalytic CO_(2)reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels.Numerous attempts have been made to produce effective and efficient photocatalysts for CO_(2)reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO_(2)reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO_(2)reduction performance in order to achieve a long-term sustainability. Metalorganic frameworks(MOFs) are recently emerging as a new type of photocatalysts for CO_(2)reduction due to their excellent CO_(2)adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO_(2)reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO_(2)reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers,and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles(NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO_(2)reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO_(2)conversion.

Ultra-fine Cu clusters decorated hydrangea-like titanium dioxide for photocatalytic hydrogen production

Hydrogen,with the merits of zero emissions and high energy density,is one of the promising green energy sources.Seeking for high efficiency and low-cost catalysts is one of the key issues for hydrogen evolution and its practical applications.Nano-structured metal cocatalysts are widely used to improve the photocatalytic performance via surface electronic structure/properties optimization of the catalyst.Herein,we report ultra-fine(*1 nm)Cu clusters decorated hydrangea-like TiO_(2)systems for photocatalytic hydrogen evolution.The pristine hydrangea-like TiO_(2)support shows a promising performance of hydrogen evolution(1.8 mmol·h^(-1)·g^(-1)),which is*10.7 times higher than that of the commercial P25(168 lmol·h^(-1)·g^(-1)).After ultra-fine Cu clusters decoration,a maximal hydrogen evolution performance(3.7 mmol·h^(-1)·g^(-1))is achieved in the optimized system 6Cu–TiO_(2)(6 wt%).Experimental and theoretical studies demonstrate that the ultra-fine Cu clusters decoration could promote the charge separation and transfer process effectively.The Cu clusters also act as reaction sites for reduction of H_(2)O to H2.These results are of great importance for the study of Cu-based co-catalyst systems and also shed light on the development of other non-noble metal co-catalysts in photocatalysis hydrogen evolution.

Liquid exfoliating CdS and MoS_(2) to construct 2D/2D MoS_(2)/CdS heterojunctions with significantly boosted photocatalytic H2 evolution activity

Fabrication of 2D/2D heterojunction photocatalysts have attracted more attentions due to their inherent merits involving the large contact interface,short charge migration distance and plentiful active sites,which are beneficial for the enhancement of photocatalytic activity.Herein,a series of 2D/2D MoS_(2)/Cd S type-I heterojunctions were prepared by incorporation the exfoliating of bulk CdS and MoS_(2) with postsintering procedure.Multiple characteristic techniques were employed to corroborate the formation of heterojunctions.By optimizing the 2D MoS_(2) amounts in the heterojunction,the 7 wt.%2D/2D MoS_(2)/CdS heterojunction displayed the maximal photocatalytic H2 evolution rate of 18.43 mmol h^(-1) g^(-1) under visible light irradiation in the presence of lactic acid as the sacrificial reagent,which was 6 times higher than that of pristine 2D CdS.Based on the photoelectrochemical and photoluminescence spectra tests,it could be deduced that the charge separation and transfer of 2D/2D MoS_(2)/CdS heterojunction was tremendously improved,and the recombination of photoinduced electron-hole pairs was effectively impeded.Moreover,the 2D MoS_(2) was used as a cocatalyst to provide the abundant active sites and lower the overpotential for H_(2) generation reaction.The current work would offer an insight to fabricate the 2D/2D heterojunction photocatalysts for splitting H_(2)O into H_(2).

Photocatalytic Hydrogen Evolution Performance for Hydroxyl-rich Porous Carbon Nitride

Metal-free photocatalyst C3N4 has been well investigated,while how to create hydroxyl-rich porous C3N4 remains a great challenge.Herein,we report a facile approach to address this issue by developing a novel two-step process:(i)precursor achieved via freeze-drying the mixture o f urea,thiourea and NH4CI;(ii)subsequent thermal polydensation o f the precursor.Systematic sample characterization demonstrated the formation o f C3N4 featured by unique hydroxyl-rich porous structure with an extended tri-s-triazine unit.When applied as photocatalyst for water splitting under UV-Vis light irradiation,the sample displays a high hydrogen evolution rate o f 243.4μmol·g^-1·h^-1about 4 times higher than that o f C3N4 prepared by conventional method.Such a performance enhancement could be due to the porous structure and surface hydroxyl-rich functional groups that promote multiple-times reflection and light absorption,increase the active site numbers,and improve carrier transfer/separation efficiency.

In situ integration of efficient photocatalyst Cu1.8S/ZnxCd1-xS heterojunction derived from a metal-organic framework

The development of photocatalysts for hydrogen evolution is a promising alternative to industrial hydrogen evolution;however,generation of high active,recyclable,inexpensive heterojunctions are still challenging.Herein,a novel strategy was developed to synthesize non-noble metal co-catalyst/solid solution heterojunctions using metal-organic frameworks(MOFs)as a precursor template.By adjusting the content of MOFs,a series of Cu1.8S/ZnxCd1-xS heterojunctions were obtained,and the Cu1.8S(3.7%)/Zn0.35Cd0.65S sample exhibits a maximum hydrogen evolution rate of 14.27 mmol h^(-1) g^(-1) with an apparent quantum yield of 3.7%at 420 nm under visible-light irradiation.Subsequently,the relationship between the heterojunction and photocatalytic activity were investigated by detailed characterizations and density functional theory(DFT)calculations,which reveal that loading Cu1.8S can efficiently extend the light absorption,meanwhile,the electrons can efficiently transfer from Zn0.35Cd0.65S to Cu1.8S,thus resulting more photogenerated electrons participating in surface reactions.This result can be valuable inspirations for the exploitation of advanced materials using rationally designed nanostructures for solar energy conversion.