Zinc–Bromine Rechargeable Batteries:From Device Configuration,Electrochemistry,Material to Performance Evaluation

Zinc–bromine rechargeable batteries(ZBRBs)are one of the most powerful candidates for next-generation energy storage due to their potentially lower material cost,deep discharge capability,non-flammable electrolytes,relatively long lifetime and good reversibility.However,many opportunities remain to improve the efficiency and stability of these batteries for long-life operation.Here,we discuss the device configurations,working mechanisms and performance evaluation of ZBRBs.Both non-flow(static)and flow-type cells are highlighted in detail in this review.The fundamental electrochemical aspects,including the key challenges and promising solutions,are discussed,with particular attention paid to zinc and bromine half-cells,as their performance plays a critical role in determining the electrochemical performance of the battery system.The following sections examine the key performance metrics of ZBRBs and assessment methods using various ex situ and in situ/operando techniques.The review concludes with insights into future developments and prospects for high-performance ZBRBs.

Preface to special column on renewable fuel synthesis by photocatalysis and photoelectrocatalysis

A renewable energy supply is an integral part of a sustainable society.The most abundant and widespread renewable energy source available on the earth,i.e.,sunlight,is intermittent and has a low energy density.This makes an economical and efficient technology to convert and store the solar energy necessary in order to utilise it on our path towards a low carbon economy.Photocatalysis and photo‐electrocatalysis can in principle store renewable solar energy into chemical bonds by diverse chemical processes,including water splitting to H_(2),nitrogen reduction to ammonia,CO_(2) reduction to chemicals and others.These chemical processes physically involve charge generation,charge separation and transfer,chemically include two half reactions and generally share the very sluggish water oxidation half reaction.The persistent kinetic challenges of these complex photophysical and photochemical processes have kept solar to fuel conversion efficiency as very moderate.

Yolk-shell Si/C composites with multiple Si nanoparticles encapsulated into double carbon shells as lithium-ion battery anodes

The conceptual design of yolk-shell structured Si/C composites is considered to be an effective way to improve the recyclability and conductivity of Si-based anode materials. Herein, a new type of yolk-shell structured Si/C composite (denoted as TSC-PDA-B) has been intelligently designed by rational engineering and precise control. In the novel structure, the multiple Si nanoparticles with small size are successfully encapsulated into the porous carbon shells with double layers benefiting from the strong etching effect of HF. The TSC-PDA-B product prepared is evaluated as anode materials for lithium-ion batteries (LIBs). The TSC-PDA-B product exhibits an excellent lithium storage performance with a high initial capacity of 2108 mAh g^-1 at a current density of 100 mA g^-1 and superior cycling performance of 1113 mAh g^-1 over 200 cycles. The enhancement of lithium storage performance may be attributed to the construction of hybrid structure including small Si nanoparticles, high surface area, and double carbon shells, which can not only increase electrical conductiv让y and intimate electrical contact with Si nanoparticles, but also provide built-in buffer voids for Si nanoparticles to expand freely without damaging the carbon layer. The present findings can provide some scientific insights into the design and the application of advanced Si-based anode materials in energy storage fields.

Design of Photobioreactors for Mass Cultivation of Photosynthetic Organisms

Photosynthetic microorganisms are important bioresources for producing desirable and environmentally benign products, and photobioreactors （PBRs） play important roles in these processes. Designing PBRs for photocatalysis is still challenging at present, and most reactors are designed and scaled up using semi- empirical approaches. No appropriate types of PBRs are available for mass cultivation due to the reactors＇ high capital and operating costs and short lifespan, which are mainly due to a current lack of deep understanding of the coupling of light, hydrodynamics, mass transfer, and cell growth in efficient reactor design. This review provides a critical overview of the key parameters that influence the performance of the PBRs, including light, mixing, mass transfer, temperature, pH, and capital and operating costs. The lifespan and the costs of cleaning and temperature control are also emphasized for commercial exploitation. Four types of PBRs-tubular, plastic bag, column airlift, and flat-panel airlift reactors are recommended for large- scale operations. In addition, this paper elaborates the modeling of PBRs using the tools of computational fluid dynamics for rational design. It also analyzes the difficulties in the numerical simulation, and presents the prospect for mechanism-based models.

Solar energy conversion on g-C3N4 photocatalyst:Light harvesting,charge separation,and surface kinetics

Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalyst, has drawn worldwide research interest in the area of solar energy conversion due to its easy synthesis, earth-abundant nature, physicochemical stability and visible-light-responsive properties. Over the past ten years, g-C3N4 based photocatalysts have experienced intensive exploration, and great progress has been achieved. However, the solar conversion efficiency is still far from industrial applications due to the wide bandgap, severe charge recombination, and lack of surface active sites. Many strategies have been proposed to enhance the light absorption, reduce the recombination of charge carriers and accelerate the surface kinetics. This work makes a crucial review about the main contributions of various strategies to the light harvesting, charge separation and surface kinetics of g-C3N4 photocatalyst. Furthermore, the evaluation measurements for the enhanced light harvesting, reduced charge recombination and accelerated surface kinetics will be discussed. In addition, this review proposes future trends to enhance the photocatalytic performance of g-C3N4 photocatalyst for the solar energy conversion.

Separator coatings as efficient physical and chemical hosts of polysulfides for high-sulfur-loaded rechargeable lithium–sulfur batteries

Lithium-sulfur batteries(LSBs)are promising alternative energy storage devices to the commercial lithium-ion batteries.However,the LSBs have several limitations including the low electronic conductivity of sulfur(5×10^-30S cm^-1),associated lithium polysulfides(PSs),and their migration from the cathode to the anode.In this study,a separator coated with a Ketjen black(KB)/Nafion composite was used in an LSB with a sulfur loading up to 7.88 mg cm^-2to mitigate the PS migration.A minimum specific capacity(Cs)loss of 0.06%was obtained at 0.2 C-rate at a high sulfur loading of 4.39 mg cm^-2.Furthermore,an initial areal capacity up to 6.70 mAh cm^-2 was obtained at a sulfur loading of 7.88 mg cm^-2.The low Cs loss and high areal capacity associated with the high sulfur loading are attributed to the large surface area of the KB and sulfonate group(SO3^-)of Nafion,respectively,which could physically and chemically trap the PSs.

Tantalum （Oxy）Nitride： Narrow Bandgap Photocatalysts for Solar Hydrogen Generation

Photocatalytic water splitting, which directly converts solar energy into hydrogen, is one of the most desirable solar-energy-conversion approaches. The ultimate target of photocatalysis is to explore efficient and stable photocatalysts for solar water splitting. Tantalum （oxy）nitride-based materials are a class of the most promising photocatalysts for solar water splitting because of their narrow bandgaps and sufficient band energy potentials for water splitting. Tantalum （oxy）nitride-based photocatalysts have experienced intensive exploration, and encouraging progress has been achieved over the past years. However, the solar- to-hydrogen （STH） conversion efficiency is still very far from its theoretical value. The question of how to better design these materials in order to further improve their water-splitting capability is of interest and importance. This review summarizes the development of tantalum （oxy）nitride-based photocatalysts for solar water spitting. Special interest is paid to important strategies for improving photocatalytic water- splitting efficiency. This paper also proposes future trends to explore in the research area of tantalum-based narrow bandgap photocatalysts for solar water splitting.

Electrochemical Surface Restructuring of Phosphorus-Doped Carbon@MoP Electrocatalysts for Hydrogen Evolution

The hydrogen evolution reaction(HER) through electrocatalysis is promising for the production of clean hydrogen fuel. However,designing the structure of catalysts,controlling their electronic properties,and manipulating their catalytic sites are a significant challenge in this field. Here,we propose an electrochemical surface restructuring strategy to design synergistically interactive phosphorus-doped carbon@MoP electrocatalysts for the HER. A simple electrochemical cycling method is developed to tune the thickness of the carbon layers that cover on MoP core,which significantly influences HER performance. Experimental investigations and theoretical calculations indicate that the inactive surface carbon layers can be removed through electrochemical cycling,leading to a close bond between the MoP and a few layers of coated graphene. The electronsdonated by the MoP core enhance the adhesion and electronegativity of the carbon layers;the negatively charged carbon layers act as an active surface. The electrochemically induced optimization of the surface/interface electronic structures in the electrocatalysts significantly promotes the HER. Using this strategy endows the catalyst with excellent activity in terms of the HER in both acidic and alkaline environments(current density of 10 mA cm^(-2) at low overpotentials,of 68 mV in 0.5 M H_(2)SO_(4) and 67 mV in 1.0 M KOH).

Progress in designing effective photoelectrodes for solar water splitting

Photoelectrochemical(PEC)water splitting process is regarded as a promising route to generate hydrogen by solar energy and at the heart of PEC is efficient electrode design.Great progress has been achieved in the aspects of material design,cocatalyst study,and electrode fabrication over the past decades.However,some key challenges remain unsolved,including the most demanded conversion efficiency issue.As three critical steps,i.e.light harvesting,charge transfer and surface reaction of the PEC process,occur in a huge range of time scale(from10-12s to100s),how to manage these subsequent steps to facilitate the seamless cooperation between each step to realize efficient PEC process is essentially important.This review focuses on an integral consideration of the three key criteria based on the recent progress on high efficient and stable photoelectrode design in PEC.The basic principles and potential strategies are summarized.Moreover,the challenge and perspective are also discussed.

Photoelectrocatalytic hydrogen peroxide production based on transition‐metal‐oxide semiconductors

As a kind of valuable chemicals,hydrogen peroxide(H2O2)has aroused growing attention in many fields.However,H2O2 production via traditional anthraquinone process suffers from challenges of large energy consumption and heavy carbon footprint.Alternatively,photoelectrocatalytic(PEC)production of H2O2 has shown great promises to make H2O2 a renewable fuel to store solar energy.Transition‐metal‐oxide(TMO)semiconductor based photoelectrocatalysts are among the most promising candidates for PEC H2O2 production.In this work,the fundamentals of H2O2 synthesis through PEC process are briefly introduced,followed by the state‐of‐the‐art of TMO semiconductor based photoelectrocatalysts for PEC production H2O2.Then,the progress on H2O2 fuel cells from on‐site PEC production is presented.Furthermore,the challenges and future perspectives of PEC H2O2 production are discussed.This review aims to provide inspiration for the PEC production of H2O2 as a renewable solar fuel.

Thermal catalysis under dark ambient conditions in environmental remediation:Fundamental principles, development, and challenges

Thermal catalytic degradation of organic pollutants conducted in the dark at room temperature under atmospheric pressure without the need of external chemicals and energy sources has attracted a lot of attention over the last two decades. It provides unparalleled advantages over other advanced oxidation processes (AOPs) in treating domestic and industrial contaminated wastewater from the viewpoint of energy/chemical conservation and ease of operation. Rich knowledge has been accumulated in terms of the synthesis and application of thermal catalysts though controversies remain regarding their underlying mechanisms. This review sheds light on the proposed thermo- catalysis mechanism for the first time and presents the development of thermal catalysts under dark ambient conditions with a focus on catalyst materials, catalytic activity, and mechanism. The present review aims to provide mechanistic insights into the rational design of novel and efficient catalysts, and their underlying mechanisms as well as the emerging challenges and perspectives in thermo-catalysis under dark ambient conditions used for the practical and efficient treatment of contaminated wastewater.

All-Climate Aluminum-Ion Batteries Based on Binder-Free MOF-Derived FeS_(2)@C/CNT Cathode

Aluminum-ion batteries(AIBs)are promising next-generation batteries systems because of their features of low cost and abundant aluminum resource.However,the inferior rate capacity and poor all-climate performance,especially the decayed capacity under low temperature,are still critical challenges toward high-specific-capacity AIBs.Herein,we report a binder-free and freestanding metal-organic framework-derived FeS_(2)@C/carbon nanotube(FeS_(2)@C/CNT)as a novel all-climate cathode in AIBs working under a wide temperature window between−25 and 50℃ with exceptional flexibility.The resultant cathode not only drastically suppresses the side reaction and volu-metric expansion with high capacity and long-term stability but also greatly enhances the kinetic process in AIBs with remarkable rate capacity(above 151 mAh g^(−1) at 2 A g^(−1))at room temperature.More importantly,to break the bottleneck of the inherently low capacity in graphitic material-based all-climate AIBs,the new hierarchical conductive composite FeS_(2)@C/CNT highly promotes the all-climate performance and delivers as high as 117 mAh g^(−1) capacity even under−25°C.The well-designed metal sulfide electrode with remarkable performance paves a new way toward all-climate and flexible AIBs.

Bismuth based photoelectrodes for solar water splitting

Photoelectrochemical water splitting is a sustainable path to generate valuable hydrogen using sunlight and water as the only inputs.Despite significant efforts to date,it is still a challenge to achieve photoelectrode with superior performance and long-term stability.Many bismuth-based semiconductor materials have demonstrated excellent visible light harvesting capability and suitable band edge for water splitting.Herein,we summarized the latest studies conducted on bismuth-based photoelectrodes for photoelectrochemical water splitting.Specifically,photoelectrochemical properties of copper bismuth oxide(CuBi_(2)O_(4)),bismuth ferrites(BiFeO_(3),Bi_(2)Fe_(4)O_(9)),bismuth vanadate(BiVO_(4)),bismuth tungstate(Bi_(2)WO_(6)),bismuth molybdate(Bi_(2)MoO_(6))and bismuth oxyhalids(BiOX,X=I,Cl,Br)are presented.Strategies to achieve high stability and photolectrochemical performance were discussed in the aspects of nanostructure formation,heterostructure assembly,practical defect engineering,preferential facet growth and oxygen evolution catalyst incorporation.

Ligand engineering of perovskite quantum dots for efficient and stable solar cells

Lead halide perovskite quantum dots(PQDs) have recently emerged as promising light absorbers for photovoltaic application due to their extraordinary optoelectronic properties. Surface ligands are of utmost importance for the colloidal stability and property tuning of PQDs, while their highly dynamic binding nature not only impedes further efficiency improvement of PQD-based solar cells but also induces intrinsic instability. Tremendous efforts have been made in ligand engineering with good hopes to solve such challenging issues in the past few years. In this review, we first present a fundamental understanding of the role of surface ligands in PQDs, followed by a brief discussion and classification of various ligands that have the potential for improving the electronic coupling and stability of PQD solids. We then provide a critical overview of recent advances in ligand engineering including the strategies of in-situ ligand engineering, postsynthesis/-deposition ligand-exchange, and interfacial engineering, and discuss their impacts on changing the efficiency and stability of perovskite QD solar cells(QDSCs). Finally, we give our perspectives on the future directions of ligand engineering towards more efficient and stable perovskite QDSCs.

Recent Advances in Printed Thin-Film Batteries

The rapidly increasing demand for wearable electronic devices has motivated research in low-cost and flexible printed batteries with diverse form factors and architectures.In the past,technological achieve-ments in the field have been emphasized,overlooking the industrial and market requirements.However,different applications require different battery chemistries and formats,that greatly impacts the manu-facturing process and competition landscape.These chemistries and formats should therefore be selected carefully to maximize the chances for commercial success.As some of these technologies are starting to be marketed for portable electronics,there is a pressing need to evaluate different printing technologies and compare them in terms of the processing constraints and product requirements of specific electronic devices.By evaluating the intrinsic strengths and current limitations of printed battery technologies,development pathways can be prioritized,and potential bottlenecks can be overcome to accelerate the path to market.

Nitrogen incorporated oxygen vacancy enriched MnCo_(2)O_(x)/BiVO_(4) photoanodes for efficient and stable photoelectrochemical water splitting

Oxygen vacancies in oxygen evolution cocatalysts(OECs)can significantly improve the photoelectrochemical(PEC)water splitting performance of photoanodes.However,OECs with abundant oxygen vacancies have a poor stability when exposing to the highly-oxidizing photogenerated holes.Herein,we partly fill oxygen vacancies in a MnCo_(2)O_(x) OEC with N atoms by a combined electrodeposition and sol-gel method,which dramatically improves both photocurrent density and stability of a BiVO_(4) photoanode.The optimized N filled oxygen vacancy-rich MnCo_(2)O_(x)/BiVO_(4) photoanode(3 at.%of N)exhibits an outstanding photocurrent density of 6.5 mA·cm^(-2) at 1.23 VRHE under AM 1.5 G illumination(100 mW·cm^(-2)),and an excellent stability of over 150 h.Systematic characterizations and theoretical calculations demonstrate that N atoms stabilize the defect structure and modulate the surface electron distribution,which significantly enhances the stability and further increases the photocurrent density.Meanwhile,other heteroatoms such as carbon,phosphorus,and sulfur are confirmed to have similar effects on improving PEC water splitting performance of photoanodes.

Reducing the vacancies associated with ferroelectric polarization to promote photocatalytic overall water splitting

Ferroelectric materials hold great promise in photocatalytic water splitting because their built-in electric field induced by the depolarization field can fulfill the separation of photogenerated carriers.However,a number of intrinsic charged vacancy defects are simultaneously generated to screen the depolarized field for stabilizing the crystal structure,always resulting in severe recombination of photogenerated carriers and thus poor overall water splitting activity.Herein,we proposed a strategy to promote the separation and transport of photogenerated carriers of ferroelectric photocatalysts by adjusting the ferroelectric polarization and altering the coordination environment of elements to reduce the defect concentration.Specifically,we prepared a series of Ta-doped PbTiO_(3)with low Pb(V_(Pb))and O(V_(O))vacancy concentrations by reducing the polarization intensity and strengthening the Pb–O interaction.The Ta-doped PbTiO_(3)shows efficient charge separation and greatly enhanced photocatalytic overall water splitting activity with the assistance of cocatalyst.This work highlights the importance of regulating ferroelectric polarization and vacancy defect concentration by the doping strategy in charge separation for photocatalytic water splitting.

Organic ligand nanoarchitectonics for BiVO_(4) photoanodes surface passivation and cocatalyst grafting

Bismuth vanadate(BiVO_(4))is a promising photoanode material for efficient photoelectrochemical(PEC)water splitting,whereas its performance is inhibited by detrimental surface states.To solve the problem,herein,a low-cost organic molecule 1,3,5-benzenetricarboxylic acid(BTC)is selected for surface passivation of BiVO_(4) photoanodes(BVOs),which also provides bonding sites for Co^(2+)to anchor,resulting in a Co-BTC-BVO photoanode.Owing to its strong coordination with metal ions,BTC not only passivates surface states of BVO,but also provides bonding between BVO and catalytic active sites(Co^(2+))to form a molecular cocatalyst.Computational study and interfacial charge kinetic investigation reveal that chemical bonding formed at the interface greatly suppresses charge recombination and accelerates charge transfer.The obtained Co-BTC-BVO photoanode exhibits a photocurrent density of 4.82 mA/cm^(2) at 1.23 V vs.reversible hydrogen electrode(RHE)and a low onset potential of 0.22 VRHE under AM 1.5 G illumination,which ranks among the best photoanodes coupled with Co-based cocatalysts.This work presents a novel selection of passivation layers and emphasizes the significance of interfacial chemical bonding for the construction of efficient photoanodes.

Chloroplast-mimicking nanoreactor for enhanced CO_(2) electrocatalysis

Producing fuels or chemicals via electrochemical carbon dioxide reduction reaction(CO_(2)RR)with renewable electricity has attracted great research interest due to its potential of alleviating the environmental and energy issues in a carbon–neutral manner[1].The CO_(2)RR is a proton-coupled electron transfer process with the simultaneous participation of multiple protons and electrons[2].

Recent progress in perovskite solar cells:material science

Perovskite solar cells represent a promising third-generation photovoltaic technology with low fabrication cost and high power conversion efficiency.In light of the rapid development of perovskite materials and devices,a systematic survey on the latest advancements covering a broad range of related work is urgently needed.This review summarizes the recent major advances in the research of perovskite solar cells from a material science perspective.The discussed topics include the devices based on different type of perovskites(organic-inorganic hybrid,all-inorganic,and lead-free perovskite and perovskite quantum dots),the properties of perovskite defects,different type of charge transport materials(organic,polymeric,and inorganic hole transport materials and inorganic and organic electron transport materials),counter electrodes,and interfacial materials used to improve the efficiency and stability of devices.Most discussions focus on the key progresses reported within the recent five years.Meanwhile,the major issues limiting the production of perovskite solar cells and the prospects for the future development of related materials are discussed.