High-Con cent rat ion Electrosynthesis of Formic Acid/Formate from CO_(2):Reactor and Electrode Design Strategies

The electrochemical CO_(2)reduction reaction(CO_(2)RR),driven by renewable energy,provides a potential carbon-neutral avenue to convert CO_(2)into valuable fuels and feedstocks.Conversion of CO_(2)into formic acid/formate is considered one of the economical and feasible methods,owing to their high energy densities,and ease of distribution and storage.The separation of formic acid/formate from the reaction mixtures accounts for the majority of the overall CO_(2)RR process cost,while the increment of product concentration can lead to the reduction of separation cost,remarkably.In this paper,we give an overview of recent strategies for highly concentrated formic acid/formate products in CO_(2)RR.CO_(2)RR is a complex process with several different products,as it has different intermediates and reaction pathways.Therefore,this review focuses on recent study strategies that can enhance targeted formic acid/formate yield,such as the all-solid-state reactor design to deliver a high concentration of products during the reduction of CO_(2)in the electrolyzer.Firstly,some novel electrolyzers are introduced as an engineering strategy to improve the concentration of the formic acid/formate and reduce the cost of downstream separations.Also,the design of planar and gas diffusion electrodes(GDEs)with the potential to deliver high-concentration formic acid/formate in CO_(2)RR is summarized.Finally,the existing technological challenges are highlighted,and further research recommendations to achieve high-concentration products in CO_(2)RR.This review can provide some inspiration for future research to further improve the product concentration and economic benefits of CO_(2)RR.

Electrochemical Degradation of o-Chloronitrobenzene by Three-dimensional Electrodes

Degradation of o-chloronitrobenzene wastewater was experimentally investigated at a three-dimensional electrode（TDE） with granular activated carbon as the particle electrode, graphite as the anode, and stainless steel plate as the cathode. The kinetic model of o-chloronitrobenzene degradation was studied, and the effects of pH, electrolysis time, particle electrode, electrolyte concentration, and initial concentration of the solution on degradation efficiency were investigated to determine the optimal operating conditions. The degradation of o-chloronitrobenzene by oxidation at the TDE was monitored by chemical oxygen demand（COD） measurements, UV-Vis absorption, and high performance liquid chromatography（HPLC）. COD degradation by electrochemical degradation followed pseudo-first order kinetics with respect to the concentration of o-chloronitrobenzene solutions. Optimal reaction conditions included 15 g of activated carbon as the particle electrode, 400 mg/L o-chloronitrobenzene solution containing 0.10 mol/L Na2SO4, pH=3, and 60 min of electrolysis. The UV-Vis absorption spectra and HPLC results illustrate that the benzene ring in o-chloronitrobenzene was rapidly broken down to form aliphatic substances through electrochemical degradation. COD degradation was approximately 98.5% at optimal conditions.

Three-dimensional vertical ZnO transistors with suspended top electrodes fabricated by focused ion beam technology

Three-dimensional(3D)vertical architecture transistors represent an important technological pursuit,which have distinct advantages in device integration density,operation speed,and power consumption.However,the fabrication processes of such 3D devices are complex,especially in the interconnection of electrodes.In this paper,we present a novel method which combines suspended electrodes and focused ion beam(FIB)technology to greatly simplify the electrodes interconnection in 3D devices.Based on this method,we fabricate 3D vertical core-double shell structure transistors with ZnO channel and Al_(2)O_(3) gate-oxide both grown by atomic layer deposition.Suspended top electrodes of vertical architecture could be directly connected to planar electrodes by FIB deposited Pt nanowires,which avoid cumbersome steps in the traditional 3D structure fabrication technology.Both single pillar and arrays devices show well behaved transfer characteristics with an Ion/Ioff current ratio greater than 106 and a low threshold voltage around 0 V.The ON-current of the 2×2 pillars vertical channel transistor was 1.2μA at the gate voltage of 3 V and drain voltage of 2 V,which can be also improved by increasing the number of pillars.Our method for fabricating vertical architecture transistors can be promising for device applications with high integration density and low power consumption.

Reaction Selectivity Improvement for Reduction of Nitrobenzene in a Packed-Bed Electrode Reactor under Periodic-Current Control

Rectangular wave current control of the electrochemical reduction of nitrobenzene im-proves the selectivity for p-aminophenol(PAP) compared to direct current(d.c.) control at thesame average current density in a flow-by packed-bed reactor.Optimal increase in PAP selectivitycan be obtained at about a frequency of 50Hz and a duty cycle of 0.2.A mathematical model isset up to incorporate the effects of mass transfer,hydrogen evolution and double layer charging,and is solved using the Duhamel’s superposition principle and the modified Crank-Nicolson methodwith the upwind scheme.The conventional d.c.control cases are also calculated for comparison.Calculations can be applied to predict the reaction results under periodic current and d.c.control,but both display the same trends compared to experimental data.

Three-Dimensional Simulation of Hydrodynamic Mechanism of Fluidized Bed Methanation

Organic solid waste(OSW)contains many renewable materials.The pyrolysis and gasification of OSW can realize resource utilization,and its products can be used for methanation reaction to produce synthetic natural gas in the specific reactor.In order to understand the dynamic characteristics of the reactor,a three-dimensional numerical model has been established by the method of Computational Fluid Dynamics(CFD).Along the height of the reactor,the particle distribution in the bed becomes thinner and the mean solid volume fraction decreases from 4.18%to 0.37%.Meanwhile,the pressure fluctuation range decreased from 398.76 Pa at the entrance to a much lower value of 74.47 Pa at the exit.In this simulation,three parameters of gas inlet velocity,operating temperature and solid particle diameter are changed to explore their influences on gas-solid multiphase flow.The results show that gas velocity has a great influence on particle distribution.When the gas inlet velocity decreases from 6.51 to 1.98 m/s,the minimum height that particles can reach decreases from 169 to 100 mm.Additionally,as the operating temperature increases,the particle holdup inside the reactor changes from 0.843%to 0.700%.This indicates that the particle residence time reduces,which is not conducive to the follow-up reaction.Moreover,with the increase of particle size,the fluctuation range of the pressure at the bottom of the reactor increases,and its standard deviation increases from 55.34 to 1266.37 Pa.

Feasibility and advantage of biofilm-electrode reactor for phenol degradation

The new biofilm-electrode method was used for the phenol degradation, because of its low current requirement. The biofilm-electrode reactor consisted of immobilized degrading bacteria on Ti electrode as cathode and Ti/PbO2 electrode as anode. With the biofilmelectrode reactor in a divided electrolytic cell, the phenol degradation rate could achieve 100% at 18 h which was higher than using traditional methods, such as biological or electrochemical methods. Chemical oxygen demand （COD） removal rate of the biofilmelectrode reactor was also greater than that using biological and electrochemical method, and could reach 80% at 16 h. The results suggested that the biofilm-electrode reactor system can be used to treat wastewater with phenol.

Numerical simulations and comparative analysis of two- and three-dimensional circulating fluidized bed reactors for CO2 capture

Carbon dioxide(CO2),the main gas emitted from fossil burning,is the primary contributor to global warming.Circulating fluidized bed reactor(CFBR)is proved as an energy-efficient method for post-combustion CO2 capture.The numerical simulation by computational fluid dynamics(CFD)is believed as a promising tool to study CO2 adsorption process in CFBR.Although three-dimensional(3D)simulations were proved to have better predicting performance with the experimental results,two-dimensional(2D)simulations have been widely reported for qualitative and quantitative studies on gas-solid behavior in CFBR for its higher computational efficiency recently.However,the discrepancies between 2D and 3D simulations have rarely been evaluated by detailed study.Considering that the differences between the 2D and 3D simulations will vary substantially with the changes of independent operating conditions,it is beneficial to lower computational costs to clarify the effects of dimensionality on the numerical CO2 adsorption runs under various operating conditions.In this work,the comparative analysis for CO2 adsorption in 2D and 3D simulations was conducted to enlighten the effects of dimensionality on the hydrodynamics and reaction behaviors,in which the separation rate,species distribution and hydrodynamic characteristics were comparatively studied for both model frames.With both accuracy and computational costs considered,the viable suggestions were provided in selecting appropriate model frame for the studies on optimization of operating conditions,which directly affect the capture and energy efficiencies of cyclic CO2 capture process in CFBR.

Effects of the Electrode Materials and Its Structure on Denitrification in a Bio-electrode Reactor

Experimental results of a denitrification process which is driven and controlled by the electric current are demonstrated in this paper. Hydrogen produced from a carbon cathode by denitrifying microorganisms adhered to the cathode surface was used to reduce nitrate to nitrogen gas. The denitrification results have close relationships with materials and structures of electrodes applied. The experimental results showed that denitrification can proceed steadily and efficiently by using carbon black as anode material, and surface roughened graphite can adhere much more biomass. The estimated energy required to remove 20mg nitrate nitrogen from 1 liter water is about 1.20×10 -4 kWh.

Electrochemical analysis and convection-enhanced mass transfer synergistic effect of MnO_x/Ti membrane electrode for alcohol oxidation

The different electrocatalytic reactors could be constructed for the electrocatalytic oxidation of 2,2,3,3-tetrafluoro-1-propanol(TFP) with two typical MnO_x/Ti electrodes, i.e.the electrocatalytic membrane reactor(ECMR) with the Ti membrane electrode and the electrocatalytic reactor(ECR) with the traditional Ti plate electrode.For the electro-oxidation of TFP, the conversion with membrane electrode(70.1%) in the ECMR was 3.3 and 1.7 times higher than that of the membrane electrode without permeate flow(40.8%) in the ECMR and the plate electrode(21.5%) in the ECR, respectively.Obviously, the pore structure of membrane and convection-enhanced mass transfer in the ECMR dramatically improved the catalytic activity towards the electro-oxidation of TFP.The specific surface area of porous electrode was 2.22 m^2·g^(-1).The surface area of plate electrode was 2.26 cm^2(1.13 cm^2× 2).In addition, the electrochemical results showed that the mass diffusion coefficient of the MnO_x/Ti membrane electrode(1.80 × 10^(-6) cm^2·s^(-1)) could be increased to 6.87 × 10^(-6) cm^2·s^(-1) at the certain flow rate with pump, confirming the lower resistance of mass transfer due to the convection-enhanced mass transfer during the operation of the ECMR.Hence, the porous structure and convection-enhanced mass transfer would improve the electrochemical property of the membrane electrode and the catalytic performance of the ECMR,which could give guideline for the design and application of the porous electrode and electrochemical reactor.

Treatment of Wastewater Containing Polyacrylamide Using Three Dimensional Electrodes

A method using three-dimensional electrode is applied to treat wastewater in oil fields, which contains polyacrylamide （PAM）, for analogue. A best condition for electrolysis （I= 1.0 A, t=90 min, c=0.1%, m=980 g,φ=5 mm, d=5.0 cm） has been determined, under which the COD removal efficiency reached 96.0%, COD containing in wastewater reduced to 64.3 mg/L from 1 622.9 mg/L, the figure before treatment. Three categories of PAM-containing wastewater in production practice have been treated with the COD removal ratios being 87.5%, 82.4% and 84.7% respectively. Presence of H2O2 and ·OH are detected by means of Ti（IV）-5-Br-PADAP technique and colorimetry respectively. The concentration is positively proportional to the COD removal ratio and increases in accordance with increment of time of electrolysis and current.

Hybrid architecture design enhances the areal capacity and cycling life of low-overpotential nanoarray oxygen electrode for lithium–oxygen batteries

Transition metal oxide(TMO)nanoarrays are promising architecture designs for self-supporting oxygen electrodes to achieve high catalytic activities in lithium-oxygen(Li-O2)batteries.However,the poor conductive nature of TMOs and the confined growth of nanostructures on the limited surfaces of electrode substrates result in the low areal capacities of TMO nanoarray electrodes,which seriously deteriorates the intrinsically high energy densities of Li-O2 batteries.Herein,we propose a hybrid nanoarray architecture design that integrates the high electronic conductivity of carbon nanoflakes(CNFs)and the high catalytic activity of Co3 O4 nanosheets on carbon cloth(CC).Due to the synergistic effect of two differently featured components,the hybrid nanoarrays(Co3 O4-CNF@CC)achieve a high reversible capacity of3.14 mA h cm-2 that cannot be achieved by only single components.Further,CNFs grown on CC induce the three-dimensionally distributed growth of ultrafine Co3 O4 nanosheets to enable the efficient utilization of catalysts.Thus,with the high catalytic efficiency,hybrid Co3 O4-CNF@CC also achieves a more prolonged cycling life than pristine TMO nanoarrays.The present work provides a new strategy for improving the performance of nanoarray oxygen electrodes via the hybrid architecture design that integrates the intrinsic properties of each component and induces the three-dimensional distribution of catalysts.

Experimental Study on Denitrification Using Coated Electrode of Immobilized Denitrifying Bacteria

Objective To develop a coated electrode of immobilized denitrificants and to evaluate the performance of a bioelectrochemical reactor to enhance and control denitrification, Methods Denitrifying bacteria were developed by batch incubation and immobilized with polyvinyl alcohol （PVA） on the surface of activated carbon fiber （ACF） to make a coated electrode. Then the coated electrode （cathode） and graphite electrode （anode） were transferred to the reactor to reduce nitrate. Results After acclimated to the mixtrophic and autotrophic denitrification stages, the denitrifying bacteria could use hydrogen as an electron donor to reduce nitrate, When the initial nitrate concentration was 30.2 mg NO3-N/L, the denitrification efficiency was 57.3% at an applied electric current of 15 mA and a hydraulic retention time （HRT） of 12 hours. Correspondingly, the current density was 0.083 mA / cm^2. The nitrate removal rate of the reactor was 34,4 g NO3-N / m^3,d, and the surface area loading was 1.34 g NO3-N / m^2.d. Conclusion The coated electrode may keep high quantity of blomass, thus achieving a high denitrification rate. Denitrification efficiencies are related to HRT, current density, oxidation reduction potential （ORP）, dissolved oxygen （DO）, pH value, and temperature,

A Mathematic Model of Gas-diffusion Electrodes in Contact with Liquid Electrolytes

A mathematic model is developed which is applied to analyze the main factors that affect electrode performance and to account for the process of reaction and mass transfer in gas-diffusion electrodes in contact with liquid electrolytes.Electrochemical Thiele modulus 2 and electrochemical effectiveness factor ηD are introduced to elucidate the effects of diffusion on electrochemical reaction and utilization of the gas-diffusion electrode.Profile of the reactant along axial direction is discussed,dependence of electrode potential V on current density Ju are predicated by means of the newly developed mathematical model.

新型电化学反应器降解苯酚废水的研究

以自制钛基PbO_(2)电极为阳极,以碳纤维管为阴极成功开发了一种基于电磁感应无线供电技术的微型电解池填充式电化学反应器,从电解质浓度、pH值和输入电压等等方面探究了新型电化学反应器对苯酚废水的最佳降解条件,当电解质浓度为0.012 5 mol/L,pH值为5,输入电压为8 V时进行降解100 min,苯酚降解率可达92%,处理效果最佳。与传统平板式电化学反应器相比具有明显优势。

基于三维生物膜电极的难生化有机化工废水处理研究进展

近年来,难降解有机化工污染物在自然水体中被广泛检出,对水生态环境和人体健康构成了严重威胁。生物膜电极技术因具备环境友好、去除效率高、适用范围广等优点,在难降解污染物处理领域应用前景日渐广阔。对此,介绍了三维生物膜电极(3D-BERs)反应器构建方法,阐述了三维生物膜电极对有机污染物的降解机理,分析了电化学催化氧化与电活性微生物(EAMs)的协同降解作用,从电子迁移强化角度解析了污染物强化降解机制,并概述了3D-BERs的构建方法与运行参数对反应器效率的影响。本文系统综述了3D-BERs在难生化有机化工废水处理领域中的应用与优势,提出了三维生物膜电极技术的发展前景和今后研究工作的重点方向,为难生化有机化工废水的高效处理提供新思路与技术选择。

Time-resolved characteristics of a nanosecond pulsed multi-hollow needle plate packed bed dielectric barrier discharge

In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.

三维电极反应器电吸附深度处理含砷废水

水环境中砷的深度处理对减少环境污染和确保人类健康至关重要。自制了三维电极反应器,以活性炭颗粒为粒子电极材料,采用电吸附和物理/化学吸附联合模式实现As(Ⅴ)的深度处理。经优化后,As(Ⅴ)浓度可从0.5 mg/L降至0.032 mg/L,且均以H_(2)AsO_(4)-形式存在,无As(Ⅲ),表明不存在氧化还原反应。动力学研究发现,电吸附过程可分为三步:从溶液到电极材料表面的液膜扩散过程、从电极材料表面到内部孔隙的内扩散过程和电吸附接近平衡状态。为验证该工艺的循环性能,开展了电吸附-电脱附工艺研究,发现经过8次循环后,出水浓度仍仅为0.098 mg/L(低于0.1 mg/L的标准限值),实现了含砷废水的高效深度处理,但去除效率需提升、吸附后材料的处理仍需改进。

Three-dimensional interconnected Ni（Fe）OxHy nanosheets on stainless steel mesh as a robust integrated oxygen evolution electrode

The development of an electrocatalyst based on abundant elements for the oxygen evolution reaction （OER） is important for water splitting associated with renewable energy sources. In this study, we develop an interconnected Ni（Fe）OxHy nanosheet array on a stainless steel mesh （SSNNi） as an integrated OER electrode, without using any polymer binder. Benefiting from the well- defined three-dimensional （3D） architecture with highly exposed surface area, intimate contact between the active species and conductive substrate improved electron and mass transport capacity, facilitated electrolyte penetration, and improved mechanical stability. The SSNNi electrode also has excellent OER performance, including low overpotential, a small Tafel slope, and long-term durability in the alkaline electrolyte, making it one of the most promising OER electrodes developed.

Chlorine-free emission disposal of spent acid etchant in a three-compartment ceramic membrane reactor

Electrochemical technologies for the on-site treatment of spent acid etchant have received great attention due their ease of operation and economic benefits. On the other hand, a large amount of Cl2 is generated during the electrolysis process, which leads to potential environmental risks. In the present work, a novel threecompartment ceramic membrane flow reactor, including a cathode chamber, an anode chamber, and a gas absorption chamber was developed. The three chambers were divided by an Al2O3 ceramic membrane and a breathable hydrophobic anode diffusion electrode(ADE). The Cl2 evolution onset potential of the ADE was increased to 1.19 V from 1.05 V of the graphite felt, effectively inhibiting the chlorine evolution reaction(CER).The anode-generated Cl2 diffused into the gas absorption chamber through the ADE and was eventually consumed by the H2O2 adsorbent. Cu could be recovered without emitting chlorine due to the special structure of reactor. The current efficiency of copper precipitation and cathode reduction from Cu2+to Cu+reached 97.7%at a working current of 150 m A. These results indicated that the novel membrane reactor had high potential for application in the copper recovery industry.

High-performance organic electrochemical transistors gated with 3D-printed graphene oxide electrodes

Organic electrochemical transistors(OECTs)have garnered significant interest due to their ability to facilitate both ionic and electronic transport.A large proportion of research efforts thus far have focused on investigating high-performance materials that can serve as mixed ion doping and charge transport layers.However,relatively less attention has been given to the gateelectrode materials,which play a critical role in controlling operational voltage,redox processes,and stability,especially in the context of semiconductor-based OECTs working in accumulation mode.Moreover,the demand for planarity and flexibility in modern bioelectronic devices presents significant challenges for the commonly used Ag/AgCl electrodes in OECTs.Herein,we report the construction of high-performance accumulation-mode OECTs by utilizing a gate electrode made of three-dimensional(3D)-printed graphene oxide.The 3D-printed graphene oxide electrode incorporating one-dimensional(1D)carbon nanotubes,is directly printed using an aqueous-based ink and showcases exceptional mechanical flexibility and porosity properties,enabling high-throughput preparation for both top gates and integrated planar architecture,as well as fast ion/charge transport.OECTs with high performance comparable to that of Ag/AgCl-gated OECTs are thus achieved and present promising feasibility for electrocardiograph(ECG)signal recording.This provides a promising choice for the application of flexible bioelectronics in medical care and neurological recording.