低自放电Cd-Ni蓄电池研制

研究了降低Cd-Ni蓄电池自放电的几个技术方法和Cd-Ni蓄电池在45℃及常温环境下的自放电对应关系。通过添加过渡金属元素Nb和Y提高正极过氧电位、采用磺酸基接枝聚丙烯隔膜、优化提高电解液Na+含量,电池自放电明显降低,常温搁置1年自放电率20%左右;研制的Cd-Ni蓄电池在45℃下搁置1个月的自放电率与常温搁置3个月自放电率相当,45℃搁置3个月的自放电率与常温搁置1年自放电率相近。

Electrochemical properties of powder-pressed Pb-Ag-PbO_(2) anodes

Pb?Ag?PbO2 composite anodes with different mass fractions(1%,2%,3%,4%and 5%)ofβ-PbO2 were prepared by powder-pressed(PP)method.The galvanostatic polarization curves,Tafel curves and anodic polarization curves were tested in sulfuric acid solution.The morphologies and phase compositions of the anodic layers formed after galvanostatic polarization were investigated by using scanning electron microscope(SEM)and X-ray diffractometer(XRD),respectively.The results showed thatβ-PbO2 can improve the electrocatalytic activity of anodic oxide.The anode containing 3%β-PbO2 had the lowest overpotential of oxygen evolution reaction(OER)and the best corrosion resistance.The morphologies of the anode surfaces were gradually transformed from regular crystals to amorphous ones as the content ofβ-PbO2 increased in anodes.

On-line Monitoring for Phosphorus Removal Process and Bacterial Community in Sequencing Batch Reactor

For efficient energy consumption and control of effluent quality, the cycle duration for a sequencing batch reactor (SBR) needs to be adjusted by real-time control according to the characteristics and loading of waste-water. In this study, an on-line information system for phosphorus removal processes was established. Based on the analysis for four systems with different ecological community structures and two operation modes, anaerobic-aerobic process and anaerobic-anaerobic process, the characteristic patterns of oxidation-reduction potential (ORP) and pH were related to phosphorous dynamics in the anaerobic, anoxic and aerobic phases, for determination of the end of phosphorous removal. In the operation mode of anaerobic-aerobic process, the pH profile in the anaerobic phase was used to estimate the relative amount of phosphorous accumulating organisms (PAOs) and glycogen accumulat-ing organisms (GAOs), which is beneficial to early detection of ecology community shifts. The on-line sensor val-ues of pH and ORP may be used as the parameters to adjust the duration for phosphorous removal and community shifts to cope with influent variations and maintain appropriate operation conditions.

Identifying the active sites in C-N codoped TiO_(2) electrode for electrocatalytic water oxidation to produce H_(2)O_(2)

Unveiling the active site of an electrocatalyst is fundamental for the development of efficient electrode material.For the two-electron water oxidation to produce H_(2)O_(2),competitive reactions,including four-and one-electron water oxidation and surface reconstruction derived from the high-oxidative environment co-existed,leading to great challenges to identify the real active sites on the electrode.In this work,Ti/TiO_(2)-based electrodes calcined under air,nitrogen,or urea atmospheres were selected as electrocatalysts for two-electron water oxidation.Electrochemical analyses were applied to evaluate the catalytic activity and selectivity.The morphological and current change on the electrode surface were determined by scanning electrochemical microscopy,while the chemical and valence evolutions with depth distributions were tested by XPS combined with cluster argon ion sputtering.The results demonstrated that Ti/TiO_(2) nanotube arrays served as the support,while the functional groups of carbonyl groups and pyrrolic nitrogen derived from the co-pyrolysis with urea were the active sites for the H_(2)O_(2) production.This finding provided a new horizon to design efficient catalysts for H_(2)O_(2) production.

Derivation of the Equation Nernst-Aibassov in a Magnetic Field

The influence of magnetic field on the redox potentials of the Nernst equation. The author offered the new formula Nernst equation in a magnetic field. Our proposed formula takes into account the influence of the magnetic field on the redox processes.

Depolarised gas anodes for aluminium electrowinning

Consumable carbon anodes are used in the electrowinning of aluminium by the Hall-Heroult process. Emissions of CO2 may be eliminated by introducing an inert oxygen evolving anode, which however will require a higher anode potential. An alternative approach is to use a natural gas or hydrogen gas anode to reduce the CO2 emissions and lower the anode potential. Preliminary laboratory experiments were carried out in an alternative molten salt electrolyte consisting of CaCl2-CaO-NaCl at 680℃ Porous anodes of platinum and tin oxide were tested during electrolysis at constant current. The behaviour of inert anode candidate materials such as tin oxide and nickel ferrite were also studied.

Stepwise dissolution of chalcopyrite bioleaching by thermophile A.manzaensis and mesophile L. ferriphilum

Chalcopyrite dissolution was evaluated by bioleaching and electrochemical experiments with thermophile A. manzaensis（Acidianus manzaensis） and mesophile L. ferriphilum（Leptospirillum ferriphium） cultures at 65 ℃ and 40 ℃, respectively. It was investigated that the bioleaching of chalcopyrite was stepwise. It was reduced to Cu2 S at a lower redox potential locating in the whole bioleaching process by A. manzaensis at high temperature while only at initial days of bioleaching by L. ferriphilum at a relative low temperature. No reduced product was detected when the redox potential was beyond a high level（e.g., 550 m V（vs SCE）） bioleached by L. ferriphilum. Chalcopyrite bioleaching efficiency was substantially improved bioleached by A. manaensis compared to that by L. ferriphilum, which was mainly attributed to the reduction reaction occurring during bioleaching. The reductive intermediate Cu2 S was more amenable to oxidation than chalcopyrite, causing enhanced copper extraction.

Control for Modified University of Cape Town Process Using Oxidation-Reduction Potential in the Second Anoxic Zone

The aim of this work is to evaluate the feasibility of applying the technology of oxidation-reduction potential （ORP） control on the municipal wastewater treatment system for nitrogen and phosphorus removal. Meanwhile the relation between the optimal ORP （ ORPopt ） and influent C/N ratio was evaluated, in which the influent chemical oxygen demand （ COD ） concentration was stabilized at （290 ± 10 ） mg/L, the influent total phosphorus （TP） concentration was stabilized at （7.0 ± 0.5 ） mg/L. The results indicated that： （1） the ORP in the second anoxic zone had effect on nitrogen and phosphorus removal capability, and the average percentages of phosphorus uptake in ANO2 zone （ ηa ） increased with increasing ORP, i. e. , increasing from 12. 0% at - 143 mV to 22.0%,30.0%,37.0%, and45.0% at -123, -111, -105 and -95 mV, respectively; （2） the ORPopt as function of influent C/N ratio could be calculated by the equation： y ffi 252. 73e〈 -x/3.39） _ 131.01 ; the maximum percentage of phosphorus uptake in ANO2 as function of the ORPopt could be calculated by the equation： y ffi -0.49e（x/15.58） ＋ 1. 51. The ORPopt was the important process control parameter that must be optimized for operation of enhanced biological phosphorus removal （ EBPR ） system. Moreover, ORP sensor is very simple, and the industrial applications of this strategy is practical.

Nitrite Accumulation during the Denitrification Process in SBR for the Treatment of Pre-treated Landfill Leachate

The nitrite accumulation in the denitrification process is investigated with sequencing batch reactor （SBR） treating pre-treated landfill leachate in anoxic/anaerobic up-flow anaerobic sludge bed I（UASB）. Nitrite accumulates obviously at different initial nitrate concentrations （64.9,54.8,49.3 and 29.5 mg·L^-1 ） and low temperatures, and the two break points on the oxidation-reduction potential （ORP） profile indicate the completion of nitrate and nitrite reduction. Usually, the nitrate reduction rate is used as the sole parameter to characterize the denitrification rate, and nitrite is not even measured. For accuracy, the total oxidized nitrogen （nitrate ＋ nitrite） is used as a measure, though details characterizing the process may be overlooked. Additionally, batch tests are conducted to investigate the effects of C/N ratios and types of carbon sources on the nitrite accumulation during the denitrification. It is observed that carbon source is sufficient for the reduction of nitrate to nitrite, but for further reduction of nitrite to nitrogen gas, is deficient when C/N is below the theoretical critical level of 3.75 based on the stoichiometry of denitrification. Five carbon sources used in this work, except for glucose, may cause the nitrite accumulation. From experimental results and cited literature, it is concluded that Alcaligene species may be contained in the SBR activated-sludge system.

Phytoremediation of PAH-Contaminated Sediments by Potamogeton Crispus L. with Four Plant Densities

In order to investigate the effect of plant density ofPotamogeton crispus L. on the remediation of sedi- ments contaminated by polycyclic aromatic hydrocarbons, a 54-day experiment with four plant densities （642, 1 604, 2 567 and 3 530 plants/m^2） was conducted. The results showed higher plant density with slower plant growth rate. Surface area per plant was the most sensitive root parameter to plant density. At the end of the 54-day experi- ment, planting P. crispus enhanced the dissipation ratios of phenanthrene and pyrene in sediments by 6.5%-26,2% and 0.95%-13.6%, respectively. The dissipation increment increased with increasing plant density. Plant uptake accounted for only a small portion of the dissipation increments. Furthermore, P. crispus could evidently improve sediment redox potentials, and strong positive correlations between root surface area and the redox potential as well as between the redox potentials and the dissipation ratios of phenanthrene and pyrene were obtained, indicating that the oxygen released by the roots ofP. crispus might be the main mechanism by which P. crispus enhanced the dis- sipation of PAHs in sediments.

Design of an Expert Control System for Biogas Fermentation Process

Controlling the biogas fermentation process is the key for maintaining stable operation of biogas system and increasing gas yield. Aiming at features of biogas fermentation process and difficulties of control, a practical control scheme is proposed combining the abundant experience of biogas experts. And it discussed the structural design and hardware configuration of the expert control system, established the database and role base, and designed the control strategy of production system inference. The design scheme with ZigBee and PDA technology as core is employed so as to solve problems of environmental factor detection and data transfer management. The test result shows that the deviation of temperature is controlled within ± 0.9℃, the deviation of pH is controlled within ±0.3, the deviation of oxidation-reduction potential is controlled within ±30mV, the deviation of gas production is controlled within ± 9mL and that of methane concentration is controlled within ±4.5%. This system is easily expandable and applicable to biogas engineering at various scales.

Synthesis of PdH0.43 nanocrystals with different surface structures and their catalytic activities towards formic acid electro-oxidation

The synthesis of nanocrystals(NCs)with defined morphology and surface structure provides an effective way to investigate the structure-activity relationship of nanocatalytsts,and it will facilitate the design of nanocatalysts with excellent catalytic performance.In this paper,we developed a facile method to synthesize PdH0.43 NCs with the shape of cube,octahedron and rhombic dodecahedron(RD),whose surface facets are{100},{111}and{110},respectively.The asprepared PdH0.43 NCs are highly stable and exhibit enhanced catalytic activity and extremely low overpotential towards electro-oxidation of formic acid compared with the commercial Pd black and three types of Pd NCs.The specific activity of the cubic PdH0.43 NCs is more than five times that of the commercial Pd black and two times that of the cubic Pd NCs.Among the three types of PdH0.43 NCs with different surface structure,the activity order is followed by PdH0.43{100}>PdH0.43{111}>PdH0.43{110}.

Highly efficient overall urea electrolysis via single-atomically active centers on layered double hydroxide

Anodic urea oxidation reaction(UOR)is an intriguing half reaction that can replace oxygen evolution reaction(OER)and work together with hydrogen evolution reaction(HER)toward simultaneous hydrogen fuel generation and urea-rich wastewater purification;however,it remains a challenge to achieve overall urea electrolysis with high efficiency.Herein,we report a multifunctional electrocatalyst termed as Rh/Ni V-LDH,through integration of nickel-vanadium layered double hydroxide(LDH)with rhodium single-atom catalyst(SAC),to achieve this goal.The electrocatalyst delivers high HER mass activity of0.262 A mg^(-1) and exceptionally high turnover frequency(TOF)of 2.125 s^(-1) at an overpotential of100 m V.Moreover,exceptional activity toward urea oxidation is addressed,which requires a potential of 1.33 V to yield 10 mA cm^(-2),endorsing the potential to surmount the sluggish OER.The splendid catalytic activity is enabled by the synergy of the Ni V-LDH support and the atomically dispersed Rh sites(located on the Ni-V hollow sites)as evidenced both experimentally and theoretically.The selfsupported Rh/Ni V-LDH catalyst serving as the anode and cathode for overall urea electrolysis(1 mol L^(-1) KOH with 0.33 mol L^(-1) urea as electrolyte)only requires a small voltage of 1.47 V to deliver 100 mA cm^(-2) with excellent stability.This work provides important insights into multifunctional SAC design from the perspective of support sites toward overall electrolysis applications.

Bimetallic oxide coupled with B-doped graphene as highly efficient electrocatalyst for oxygen evolution reaction

Developing electrocatalysts with high performance and low cost for the oxygen evolution reaction(OER)is of great importance for fabricating renewable energy storage and conversion devices.Here,a series of boron-doped graphene(BG)-supported bimetallic oxides of Co and Ni were obtained and served as OER electrocatalysts.Surprisingly,the annealed Co-Ni-Ox/BG with a Co/Ni ratio of 1:1 exhibits high performance toward oxygen evolution in alkaline electrolyte.The overpotential is only 310 mV at the current density of 10 mA cm-2,superior to many mono-metallic oxides reported before,and even comparable to the commercial RuO2.The regulation of charge distribution in bimetallic oxides and the strong synergistic coupling effects together contribute to the superior electrocatalytic performance of the Co-Ni-Ox/BG toward OER.This study also offers several effective ways to design high-performance OER electrocatalysts for water splitting.

3D ordered mesoporous cobalt ferrite phosphides for overall water splitting

Developing low-cost and earth-abundant electrocatalysts with high performance for electrochemical water splitting is a challenging issue. Herein, we report a facile and effective way to fabricate three-dimension(3D) ordered mesoporous Co1-xFexP(x=0, 0.25, 0.5, 0.75) electrocatalyst.Benefiting from 3D ordered mesoporous pore channels and composition optimization, the Co0.75Fe0.25 P exhibits excellent electrocatalytic activities with low overpotentials of 270 and 209 mV at 10 mA cm^-2 for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER), respectively, in the alkaline electrolyte along with a durable electrochemical stability. In addition, as both the cathode and anode, the Co0.75Fe0.25P also exhibits superior electrolysis water splitting performance with only an applied voltage of 1.63 V to attain a current density of 10 m A cm^-2 without obvious decay for 18 h,indicating that the Co0.75Fe0.25P is an efficient electrocatalyst for overall water splitting.

Interface engineering of snow-like Ru/RuO2 nanosheets for boosting hydrogen electrocatalysis

Ru has recently been regarded as a promising catalyst for hydrogen oxidation reaction(HOR) and hydrogen evolution reaction(HER) due to its similar binding energy towards *H but lower price compared to Pt.Nevertheless, the quest of high-efficiency Ru-based catalysts for HOR and HER is driven by the current disadvantages including low activity and unsatisfactory stability. Herein, we have fabricated and engineered two-dimensional(2D) Ru-based snow-like nanosheets with Ru/Ru O2interface(Ru/Ru O2SNSs)via a post-annealing treatment. Detailed characterizations and theoretical calculations indicate that the interfacial synergy, which is dependent on the temperature for annealing, can alter the hydrogen binding energy(HBE) and hydroxide binding energy(OHBE), as a result of the enhanced HOR and HER performance. Impressively, the optimal Ru/RuO_(2) SNSs display a mass activity of 9.13 A mgRu^(–1) at an overpotential of 50 m V in 0.1 mol L^(–1) KOH for HOR, which is 65, 304, and 21 times higher than those of Ru SNSs(0.14 A mg_(Ru)^(–1)), RuO_(2) SNSs(0.03 A mg_(Ru)^(–1)), and commercial Pt/C(0.43 A mg_(Ru)^(–1)), respectively.Moreover, Ru/RuO_(2) SNSs display improved HER activity with a low overpotential of 20.2 m V for achieving10 m A cm^(-2)in 1 mol L^(–1)KOH. This work not only provides an efficient catalyst for HOR and HER, but also promotes fundamental research on the fabrication and modification of catalysts in heterogeneous catalysis.

Importance of Au nanostructures in CO2 electrochemical reduction reaction

Electrochemical conversion of CO2 into fuels is a promising means to solve greenhouse effect and recycle chemical energy. However, the CO2 reduction reaction(CO2 RR) is limited by the high overpotential, slow kinetics and the accompanied side reaction of hydrogen evolution reaction. Au nanocatalysts exhibit high activity and selectivity toward the reduction of CO2 into CO. Here, we explore the Faradaic efficiency(FE)of CO2 RR catalyzed by 50 nm gold colloid and trisoctahedron. It is found that the maximum FE for CO formation on Au trisoctahedron reaches 88.80% at -0.6 V, which is 1.5 times as high as that on Au colloids(59.04% at -0.7 V). The particle-size effect of Au trisoctahedron has also been investigated, showing that the FE for CO decreases almost linearly to 62.13% when the particle diameter increases to 100 nm. The Xray diffraction characterizations together with the computational hydrogen electrode(CHE) analyses reveal that the(2 2 1) facets on Au trisoctahedron are more feasible than the(1 1 1) facets on Au colloids in stabilizing the critical intermediate COOH*, which are responsible for the higher FE and lower overpotential observed on Au trisoctahedron.

Oxygen vacancies in metal oxides: recent progresstowards advanced catalyst design

Energy crisis and environmental problems urgently drive the proposal of new strategies to improve human wellbeing and assist sustainable development.To this end,scientists have explored many metal oxides-based photocatalysts with high stability,low cost,earth abundance,and potentially high catalytic activity relevant for key applications such as H2O splitting,CO2 reduction,N2 fixation,and advanced oxidation of pollutants.In these metal oxides,oxygen vacancies(OVs)are ubiquitous and intrinsic defects with pronounced impacts on the physicochemical properties of the catalysts,which may open new opportunities for obtaining efficient metal oxides.The thorough understanding of the structural and electronic nature of OVs is necessary to determine how they serve as catalytically active sites.In this review,we summarize the origin of OVs,the strategies to introduce OVs,as well as the fundamental structure-activity relationships to relate these crystal defects to catalyst properties including light absorption,charge separation,etc.We emphasize the mechanism of OVs formation and their effects on the intrinsic catalytic characteristics of the metal oxides.We also present some multicomponent catalytic platforms where OVs contribute to catalysis via synergy.Finally,opportunities and challenges on engineering defects in photocatalysts are summarized to highlight the future directions of this research field.

Reversible LiOH chemistry in Li-O_(2)batteries with free-standing Ag/δ-MnO_(2)nanoflower cathode

The low energy efficiency and poor cycle stability arising from the high aggressivity of discharge products toward organic electrolytes limit the practical applications of Li-O_(2)batteries(LOBs).Compared with the typical discharge product Li_(2)O_(2),LiOH shows better chemical and electrochemical stability.In this study,a free-standing cathode composed of hydrangea-likeδ-MnO_(2)with Ag nanoparticles(NPs)embedded in carbon paper(CP)(Ag/δ-MnO_(2)@CP)is fabricated and used as the catalyst for the reversible formation and decomposition of LiOH.The possible discharge mechanism is investigated by in situ Raman measurement and density functional theory calculation.Results confirm thatδ-MnO_(2)dominantly catalyzes the conversion reaction of discharge intermediate LiO_(2)*to LiOH and that Ag particles promote its catalytic ability.In the presence of Ag/δ-MnO_(2)@CP cathode,the LOB exhibits enhanced specific capacity and a high discharge voltage plateau under humid O_(2)atmosphere.At a current density of 200 mA g^(−1),the LOB with the Ag/δ-MnO_(2)@CP cathode presents an overpotential of 0.5 V and an ultra-long cycle life of 867 cycles with a limited specific capacity of 500 mA h g^(−1).This work provides a fresh view on the role of solid catalysts in LOBs and promotes the development of LOBs based on LiOH discharge product for practical applications.

Bacterial cellulose-regulated synthesis of metallic Ni catalysts for high-efficiency electrosynthesis of hydrogen peroxide

The decentralized production of H_(2)O_(2) via a twoelectron oxygen reduction reaction(2e^(-)ORR)has emerged as a promising alternative to the energy-intensive anthraquinone(AQ)process.However,its practical application requires 2eORR electrocatalysts with high activity and selectivity.Herein,we report the synthesis of metallic Ni nanoparticles anchored on bacterial cellulose-derived carbon fibers(Ni-NPs/BCCF)via a facile impregnation-pyrolysis method as efficient electrocatalysts for 2 e-ORR to H_(2)O_(2).By tuning the amount of Ni precursor,the best electrocatalytic performance toward 2 eORR was achieved for Ni-NPs/BCCF-20.7,affording a high H_(2)O_(2) selectivity of ~90% and an onset potential of 0.75 V vs.reversible hydrogen electrode(RHE)in an alkaline electrolyte.Ni-NPs/BCCF-20.7 achieved the largest H_(2)O_(2) yield rate of 162.7±13.7 mmol gcat^(-1)h^(-1) and the highest Faradaic efficiency of 93.9%±4.2% at 0.2 and 0.5 V vs.RHE from the bulk ORR system,respectively.Theoretical calculations revealed the more favorable"end-on"adsorption configuration of molecular oxygen on the exposed Ni(111)plane,which can effectively suppress the O-O bond dissociation,resulting in high selectivity for H_(2)O_(2) generation.