Preparation and application of perovskite-type oxides for electrocatalysis in oxygen/air electrodes

Recent advances in the preparation and application of perovskite-type oxides as bifunctional electrocatalysts for oxygen reaction and oxygen evolution reaction in rechargeable metal-air batteries are presented in this review.Various fabrication methods of these oxides are introduced in detail,and their advantages and disadvantages are analyzed.Different preparation methods adopted have great influence on the morphologies and physicochemical properties of perovskite-type oxides.As a bifunctional electrocatalyst,perovskite-type oxides are widely used in rechargeable metal-air batteries.The relationship between the preparation methods and the performances of oxygen/air electrodes are summarized.This work is concentrated on the structural stability,the phase compositions,and catalytic performance of perovskite-type oxides in oxygen/air electrodes.The main problems existing in the practical application of perovskite-type oxides as bifunctional electrocatalysts are pointed out and possible research directions in the future are recommended.

Air flow control based on optimal oxygen excess ratio in fuel cells for vehicles

Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio （OER） is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.

Applicable scope of oxygen-reduced air flooding and the limit of oxygen content

The mechanisms of oxygen-reduced air flooding(ORAF)and the explosion limit and the corrosion control approaches were studied based on the pilots of oxygen-reduced air flooding(ORAF)in the Dagang,Changqing and Daqing oil fields in China.On the foundation of indoor investigations and pilots,the explosion limits,oxygen reduction limits and corrosion control approaches were clarified.When the temperature of reservoir is equal to and higher than 120℃,there is a violent reaction between oxygen and crude oil,that means the effect of low temperature oxidation would be fully taken use of to enhance oil recovery by air flooding directly;nitrogen dominated immiscible flooding with oxygen-reduced air should be applied in cases where reservoir temperature is below 120℃ with little oxygen consumption and little heat generated.The oxygen-reduced air flooding is suitable for 3 types of reservoirs:low permeability reservoir,water flooding development reservoir of high water-cut and high temperature and high salinity reservoir.In the process of development,in order to ensure safety,the oxygen reduction limits should be controlled fewer than 10%,while oxygen-reduced air can obviously reduce the corrosion rate of pipes;The surface pipelines and injection wells don’t need to consider about oxygen corrosion with no water,special materials and structure of pipe or corrosion inhibitor can be applied to the surface pipelines and injection wellbores with water.Air/oxygen-reduced air is a low-cost displacement medium and it could be applied in many special conditions of low permeability reservoir for energy supplement,huff and puff and displacement,that means oxygen-reduced air flooding has become the most potential strategic technology in 20 years.

Significantly enhanced oxygen reduction activity of Cu/CuN_xC_y co-decorated ketjenblack catalyst for Al–air batteries

Highly efficient and non-precious catalysts are imperative for oxygen reduction reaction（ORR） to replace Pt/C. Anchoring efficient active species to carbon supports is a promising and scalable strategy. Here we synthesize Cu nanoparticles and noncrystalline CuNxCy species co-decorated ketjenblack（KB） carbon catalyst（denoted as Cu-N-KB-acid） by a facile and scalable method using copper sulfate, melamine, and KB as raw materials. An initial one-pot hydrothermal treatment is designed before pyrolysis process to achieve the good distribution of Cu and melamine on KB via a possible chelation effect. Owing to the synergistic effect of Cu and CuNxCy on KB, this composite catalyst displays excellent ORR catalytic activity in alkaline solution, which is comparable to the commercial 20% Pt/C. When used as a catalyst in a home-made Al-air battery, it shows a stable discharge voltage of 1.47 V at a discharge density of 50 mA cm-2, a little higher than that of Pt/C（1.45 V）.

Nitrogen-doped carbon nanotube encapsulating cobalt nanoparticles towards efficient oxygen reduction for zinc–air battery

Nitrogen-doped carbon materials encapsulating 3 d transition metals are promising alternatives to replace noble metal Pt catalysts for efficiently catalyzing the oxygen reduction reaction(ORR). Herein, we use cobalt substituted perfluorosulfonic acid/polytetrafluoroethylene copolymer and dicyandiamide as the pyrolysis precursor to synthesize nitrogen-doped carbon nanotube(N–CNT) encapsulating cobalt nanoparticles hybrid material. The carbon layers and specific surface area of N–CNT have a critical role to the ORR performance due to the exposed active sites, determined by the mass ratio of the two precursors. The optimum hybrid material exhibits high ORR activity and stability, as well as excellent performance and durability in zinc–air battery.

Quantitative Determination of Density of Ground State Atomic Oxygen from Both TALIF and Emission Spectroscopy in Hot Air Plasma Generated by Microwave Resonant Cavity

Two experimental techniques have been used to quantify the atomic oxygen density in the case of hot air plasma generated by a microwave （MW） resonant cavity. The latter operates at a frequency of 2.45 GHz inside a cell of gas conditioning at a pressure of 600 mbar, an injected air flow of 12 L/min and an input MW power of 1 kW. The first technique is based on the standard two photon absorption laser induced fluorescence （TALIF） using xenon for calibration but applied for the first time in the present post discharge hot air plasma column having a temperature of about 4500 K near the axis of the nozzle. The second diagnostic technique is an actinometry method based on optical emission spectroscopy （OES）. In this case, we compared the spectra intensities of a specific atomic oxygen line （844 nm） and the closest wavelength xenon line （823 nm）. The two lines need to be collected under absolutely the same spectroscopic parameters. The xenon emission is due to the addition of a small proportion of xenon （1% Xe） of this chemically inert gas inside the air while a further small quantity of H2 （2~） is also added in the mixture in order to collect OH（A- X） and NH（A-X） spectra without noise. The latter molecular spectra are required to estimate gas and excitation temperatures. Optical emission spectroscopy measurements, at for instance the position z=12 mm on the axis plasma column that leads to a gas measured temperature equal to 3500 K, an excitation temperature of about 9500 K and an atomic oxygen density 2.09× 1017＋ 0.2×1017 cm-3. This is in very good agreement with the TALIF measurement, which is equal to 2.0×101T cm-3.

Unexpected complication during extracorporeal membrane oxygenation support: Ventilator associated systemic air embolism

Systemic air embolism through a bronchovenous fistu-la(BVF) has been described in patients undergoing positive-pressure ventilation. However, no report has mentioned the potential risks of systemic air embolism through a BVF in patients undergoing extracorporeal membrane oxygenation(ECMO). Positive-pressure ventilation and ECMO support in patients with lung injury can increase the risk of systemic air embolism through a BVF. Increased alveolar pressure, decreased pulmonary venous pressure, and anticoagulation are thought to be the factors that contribute to this complication. Here, we present a case of systemic air embolism in a patient with ECMO and mechanical ventilator support.

塔中深层稠油在不同氧含量下的动力学特征研究

原油在减氧空气中发生氧化反应的过程复杂,准确分析油藏条件下原油氧化反应动力学特征十分重要。为实现对油藏条件下原油氧化反应的准确分析,需进行定性与定量综合研究。采用差示扫描量热法(DSC)、热重法(TG)等定性与定量测试方法,综合研究塔中深层稠油油藏在不同氧含量下的氧化机理、氧化放热、失重和动力学特征。DSC实验结果表明,氧含量的提升对原油的氧化热效应促进明显,原油的氧化放热量与峰值热流量随着氧含量的升高而大幅增加。TG实验表明,随着氧含量的升高,原油的低温氧化区间不断缩短,低温氧化阶段的质量消耗减少。低温氧化区间的温度范围随静态氧化时减氧空气中氧含量的升高(氧化程度的加深)而逐渐变窄。基于TG实验数据,使用微分法Friedman和微分法OFW求取的原油低温氧化阶段活化能接近,且活化能均随转化率的升高而增加,塔中深层稠油在氧含量为5%的减氧空气中低温氧化阶段平均活化能为81.04 kJ/mol。

考虑变掺氧富氧燃烧与利用LNG冷能的LAES的综合能源系统低碳经济调度

为促进风电消纳,减少火电机组的碳排放,解决综合能源系统(Integrated Energy System,IES)低碳经济运行问题,文中引入变掺氧富氧燃烧技术对燃气机组进行改造,并结合利用液化天然气(Liquefied Natural Gas,LNG)冷能的液化空气储能(Liquid Air Energy Storage,LAES),提出了一种电热气冷IES低碳经济优化策略。首先,构建含变掺氧富氧燃烧燃气机组、利用LNG冷能的LAES、电转气(Power To Gas,P2G)设备、中央空调和溴化锂制冷机的IES架构,并建立各设备的数学模型;其次,引入阶梯式碳交易机制,建立了以系统运行成本最小为目标的电热气冷IES低碳经济调度模型;最后,采用MATLAB调用GUROBI求解器对多个场景进行求解,验证了文中提出的低碳经济优化调度策略可以提高系统的风电消纳、有效降低系统运行成本,实现碳减排。

浅埋深综放工作面采空区“三带”分布研究

为研究浅埋深综放工作面采空区“三带”分布规律,在串草圪旦煤矿6101综放工作面采空区埋设束管,对采空区“三带”进行了现场实测。实测结果表明:由于煤层埋深浅、地表起伏大、进风侧存在地表漏风,进风侧采空区“三带”明显滞后于回风侧,进回风两侧氧化带宽度分别为87.8 m和61.4 m。利用FLUENT软件对实测条件下该工作面采空区“三带”进行了数值模拟,模拟结果和现场实测结果基本一致。同时模拟了不漏风条件下该工作面采空区“三带”分布,此时采空区散热带、氧化带范围大幅度减小,进风侧采空区氧化带稍大,而工作面中部和回风侧“三带”分布基本一致。

污水曝氧工艺技术研究

大庆油田聚驱用聚合物常使用含聚污水进行调配,但含聚污水中存在大量S^(2-)、Fe^(2+)等离子,会对聚合物分子产生严重的降解作用,造成稀释母液时降低溶液黏度,影响驱油效果。为有效清除溶液中还原性离子含量,可采用曝氧工艺对含聚污水进行处理。通过实验,将曝氧气头换为盘式曝氧器,重新设计工艺流程,可提高曝氧效率,节约能耗。盘式曝氧工艺在气水比5∶1,曝氧时间3~6 h条件下,污水溶氧量达到5 mg/L以上,配制黏度提高7.6%以上,能有效降低含聚采出水中的还原性物质含量,聚合物溶液稳定性大幅提升,保证聚驱稀释用水溶氧值满足开发效果。

塔中深层稠油减氧空气驱氧化特征及机理研究

针对塔中深层稠油油藏开展静态氧化实验,通过测试分析不同氧含量与不同氧化时间下产出油气组成,研究了油藏注减氧空气过程中原油与减氧空气的氧化特征、氧化途径与氧化机理。实验结果表明,原油的耗氧速率与减氧空气的氧含量呈正相关,与氧化时间呈负相关;二氧化碳的生成量随氧化时间与减氧空气氧含量的增加而增大;原油与减氧空气的反应会一定程度上使原油黏度增加,其黏度增加的幅度随减氧空气氧含量的升高和氧化时间的增长而增大;氧化后原油饱和烃与芳香烃的含量减少,胶质与沥青质的含量增加,且沥青质增加更为明显。原油在氧化后出现了C=O的伸缩振动峰,且振动峰随着减氧空气氧含量的增加而增强,说明原油在氧化过程中发生了加氧反应生成了醛类等物质,且氧化反应随着氧含量的升高而不断加深。

乙烯富燃燃气/富氧空气旋转爆轰自起爆现象研究

对高温乙烯富燃燃气与富氧空气进行旋转爆轰自起爆过程进行了实验研究。实验抛弃了传统的预爆轰管起爆方式,高温乙烯富燃燃气经过喷注与外壁面碰撞产生局部“热点”,点燃混合气体形成爆燃状态。在壁面摩擦作用以及燃烧室头部激波反射的综合作用下,爆燃火焰最终会通过爆燃转爆轰过程转变为爆燃/爆轰混合模态,生成稳定传播的旋转爆轰波。当量比会对自起爆成功率造成影响。富氧空气含氧量在40%时,当量比0.52~1.84内发动机均可成功起爆。随着富氧空气含氧量的提升,旋转爆轰波模态分别经历双波对撞、单波以及爆燃/爆轰混合模态。富氧空气含氧量变大会使得爆轰波传播速度增大,富氧空气含氧量为47.4%时获得最大爆轰波传播速度1 790.6 m/s。

扬州城市森林负氧离子分布变化特征及其与气象因素的关系

【目的】分析扬州城市森林空气负氧离子浓度时空变化特征及其与气象因素的关系,为了解扬州城市森林空气负氧离子资源情况提供理论依据。【方法】依托江苏扬州城市森林生态系统国家定位观测研究站,以宋夹城体育休闲公园(城市森林)、茱萸湾风景区(城市近郊森林)和润扬湿地森林公园(城市远郊森林)为研究对象,收集3个区域的2020年1—12月空气负氧离子浓度和林内气象数据,比较不同季节之间负氧离子浓度的差异,分析负氧离子浓度与气象因素的相关性,并利用增强回归树分析各气象因素对负氧离子浓度的贡献率,结构方程模型分析各气象因素对负氧离子的直接和间接影响。【结果】扬州地区城市近郊森林区的空气负氧离子浓度日变化呈单峰型;城市近郊森林区与城市远郊森林区月变化趋势较一致,峰值分别出现在4月和6月。城市近郊森林区不同季节平均负氧离子浓度表现为春季>冬季>夏季>秋季,城市远郊森林区平均负氧离子浓度表现为夏季>冬季>春季>秋季。城市远郊森林区林内负氧离子浓度年平均值(666.87个/cm3)和郁闭度(0.80)低于城市森林区和城市近郊森林区,且森林郁闭度越高其负氧离子浓度的变异系数越小。城市森林区空气负氧离子浓度与风速、气压、空气温度和PM2.5存在显著(P<0.05,下同)或极显著(P<0.01,下同)相关性,城市近郊森林区和城市远郊森林区的空气负氧离子浓度与气压、风速、空气温度、空气湿度、PM2.5、光照强度等林内气象因素存在显著或极显著相关性。选择城市远郊森林区进行气象因素对空气负氧离子浓度的贡献率以及结构方程模型分析,结果表明空气湿度在春季(38.51%)和秋季(47.58%)对空气负氧离子浓度的贡献最大,而PM2.5在夏季(27.87%)和冬季(38.51%)对空气负氧离子的贡献最大;空气湿度对负氧离子浓度有直接正向影响,而光照强度对负氧离子浓度有直接负向影响,风向通过改变PM2.5对负氧离子浓度产生间接影响。【结论】扬州不同区域森林的负氧离子浓度变化规律不尽相同,不同季节和时间对空气负氧离子浓度有明显影响。根据不同区域的负氧离子浓度差异及其表现出的季节变化规律可制定不同的公园游览计划,建议夏季前往城市远郊森林区,春季前往城市近郊森林区游览。

减氧空气驱集输管道抗氧缓蚀剂优选与评价

目前抗氧缓蚀剂存在种类稀少、单一种类缓蚀剂的性能不够好以及经济成本较高等一系列问题。为此,结合国内某减氧空气驱集输管道实际工况特点,通过对氧腐蚀机理研究,选取了3种现已研发的油田常用抗氧缓蚀剂EQI、HTT和TCT,对其进行了动态腐蚀评价试验和表面形貌分析,通过分子动力学模拟其在Fe表面的吸附情况,得到缓蚀剂分子在水溶液环境下对Fe基体表面的吸附能大小,结合对比分析模拟和试验的结果,筛选出缓蚀性能最佳的缓蚀剂。试验和模拟结果均表明:水溶液中3种缓蚀剂分子在Fe基体表面的吸附能大小从高到低依次为TCT>EQI>HTT,缓蚀剂分子吸附能越大,缓蚀性能越佳。所得结论可为减氧空气驱集输系统的腐蚀防护工作提供理论指导。

减氧空气驱油集输管线缓蚀剂防腐评价研究

减氧空气驱能有效提高低渗透油藏的采收率,但氧气的存在也必然造成下游的集输管线氧腐蚀和CO_(2)腐蚀,从而限制了减氧空气驱的推广应用。针对国内某应用减氧空气驱油田集输管线,开展了缓蚀剂防腐研究。在模拟现场集输管道工况条件下,采用挂片动态失重法,选取了6种抗CO_(2)缓蚀剂和6种抗氧缓蚀剂对20钢材的缓蚀作用进行评价筛选。实验初选了两种抗氧缓蚀剂KY-12和KY-17以及一种抗CO_(2)缓蚀剂A,三者的缓蚀率分别达到了83.67%、91.49%和78.44%。通过对初选的3种缓蚀剂在不同温度(25、40和55℃)和不同浓度(400、500、800、1000和2000 mg/L)条件下的实验评价,优选出在不同温度情况下稳定性最佳的KY-17缓蚀剂,且在不同浓度时缓蚀效果最好,缓释率最高达到92.7%。该结论对于减氧空气驱油田下游集输管线缓蚀剂的选型和加剂量有较好的参考意义。

ZnO修饰碳基复合纳米材料的制备及其在锌-空气电池中的应用

作为一种新兴的能源技术,可充电金属-空气电池因具有循环转换电能与化学能的能力而备受关注,并在替代传统金属离子电池方面具有广阔的应用前景。然而,可充电金属-空气电池的实际应用受到阴极氧化还原反应速率缓慢、Pt/C金属催化剂成本高昂及稳定性不佳等因素的制约。基于此,本研究报道了一种简便制备锌-空气电池廉价阴极催化剂的方法,采用富含氮的苯甲酸铵作为前驱体,通过一锅法热解成功合成了ZnO修饰碳基复合纳米电催化剂(ZnO/NC-800)。电化学测试结果表明,该催化剂在碱性电解液中表现出优异的氧还原催化活性,且稳定性和安全性较好,ZnO/NC-800催化剂组装的锌-空气电池表现出与碳载铂电池相媲美的性能。

N80钢在模拟减氧空气驱生产井中的腐蚀行为

为了探究N80钢在减氧空气驱生产井中的腐蚀行为,基于灰色关联分析法,分析了国内某减氧空气驱生产井的腐蚀主控因素,并以油藏模拟结果作为室内模拟参数,采用动态失重法结合金相显微镜、XRD、3D形貌等相关表征,研究了不同生产时期N80钢的腐蚀行为。结果表明:氧含量对减氧空气驱生产井腐蚀的敏感性最大,在含氧工况下,N80钢的腐蚀速率显著增加,氧含量3%(0.3 MPa)时的腐蚀速率是不含氧的5倍左右。在驱油初期,腐蚀为CO_(2)主导的局部腐蚀,腐蚀产物主要为致密的FeCO_(3)。随着注气时间的延长,井筒内为CO_(2)/O_(2)均衡环境,腐蚀转变为二者共同作用,腐蚀产物为FeCO_(3)和疏松多孔的Fe_(2)O_(3)。在持续注气3年后,生产井内为高O_(2)+低CO_(2)环境,致密的FeCO_(3)遭到破坏,腐蚀坑横向发展,腐蚀转变为由O_(2)主导的全面腐蚀。

减氧空气驱套管寿命校核方法与实践应用

减氧空气驱油工艺可有效提升油井产量,但也加剧了井内流体对套管的腐蚀,是后续生产重大风险源之一。从套管设计问题切入,考虑磨损、腐蚀引起壁厚损失,得出老井套管剩余壁厚;开展多种套管钢材挂片腐蚀实验,给出了适用于目标油田减氧空气驱的套管寿命校核图版,对套管使用寿命进行预测。结果显示,Cr钢对减氧空气驱腐蚀有一定的抑制作用;在减氧空气驱生产工况下原井套管无法长期生产。

承德北部空气负氧离子浓度特征及预报模型

利用承德北部丰宁县2020年1月1日—2022年5月31日2个空气负氧离子站监测资料,以及同期的气象环境数据,分析负氧离子浓度时间变化特征、与气象环境要素的时序关系及关键影响因素,建立负氧离子浓度的预测模型。结果表明:丰宁城市公园、林区的负氧离子浓度年均值分别为1358.7、1955.8个/cm^(3),日平均最大值分别为3867、5845个/cm^(3),具有治疗和康复功效的自然环境条件;城市公园和林区的负氧离子浓度月变化均呈“单峰”型分布,峰值分别出现在7月(1889.5个/cm^(3))、8月(2516.3个/cm^(3)),最小值均出现在1月,林区各月浓度明显高于城市公园;负氧离子浓度日变化均呈“双峰”型,峰值分别出现在06时及20时前后,最小值出现在14时前后,夜间浓度均大于白天;城市公园、林区的负氧离子浓度与气温、降水量、相对湿度、风速、日照及PM_(2.5)、O_(3)浓度显著相关,城市公园受气象环境要素影响更大;利用多元回归方法,分别建立城市公园和林区的负氧离子浓度预报模型,2个模型的预报准确率>70%的占比分别为80.9%、73.7%,拟合效果良好。