直接碳燃料电池技术研究进展分析

直接碳燃料电池(Direct Carbon Fuel Cell,DCFC)能够直接将固体碳燃料中的化学能高效、清洁地转化为电能,对煤炭的合理利用、污染物控制以及CO2减排具有重要意义。目前已开发出以熔融碳酸盐、熔融氢氧化物和固体氧化物作为电解质的多种DCFC,但与其它燃料电池技术相比,研究尚处于起步阶段。本文综述了DCFC技术的发展历程及研发现状,对现有DCFC加以分类,分析比较了其各自工作机理、性能特点以及在CO2减排方面的特性。在总结各类DCFC所面临的技术难题基础上,展望了直接碳燃料电池技术今后可能的发展方向。     

氢能发电技术的研究（Ⅰ）——铂碳复合电极材料对离子交换膜燃料电 …

离子交换膜燃料电池是氢能应用开发的重要研究领域。研究了离子交换膜燃料电池用的铂碳复合电极制备工艺和碳材料的选择对燃料电化学性能的影响。研究结果表明,铂碳复合电极的制备工艺对燃料电池放电性能有重要影响,采用刷涂法和物化法制备的铂碳复合电极所组装的燃料电池具有较好的电化学性能。研究结果还发现,复合电极中碳材料的微观结构也是影响燃料电池化学性能的重要因素,碳材料的比表面积越大,燃料电池的放电性能就越好。     

直接碳固体氧化物燃料电池研究进展:碳燃料和逆向Boudouard反应催化剂

直接碳固体氧化物燃料电池(direct carbon solid oxide fuel cells,DC-SOFCs)是一种能够将固体碳中的化学能直接转化为电能的新型能量转换装置,具有理论效率高、燃料来源广泛、成本低以及绿色环保等突出优势.根据DC-SOFC的工作原理,其运行过程是一个动力学控制步骤,即阳极侧CO的电化学氧化反应与碳燃料中逆向Boudouard反应的有效耦合保证了DC-SOFC的高效稳定运行.其中,速率相对较慢的逆向Boudouard反应是电池电化学性能的决定因素.因此,设计提高逆向Boudouard反应速率是促进DC-SOFC产业化进程的有效途径,也是发展趋势.国内外研究者采取了一系列措施来实现此目标,其中最简单有效的两种方法是:①在固体碳燃料中担载逆向Boudouard反应催化剂;②直接采用多孔结构且天然富含金属元素的生物质炭为燃料.基于近年来的前沿研究,本文综述了采用不同类型逆向Boudouard反应催化剂和碳燃料的DC-SOFCs最新研究进展,系统总结了DC-SOFCs的研究现状、面临的挑战和未来发展方向,以期为开发高性能、长寿命DC-SOFCs提供有价值的参考.     

直接碳燃料电池(DCFC)实验研究

直接碳燃料电池是一种高效、清洁的燃料电池技术,其原理是碳和氧气勿需气化和重整而直接通过电化学反应产生电能,效率可达80%,燃料利用率约达100%。自行组装了DCFC单体电池,工作温度为500～700℃;该电池采用熔融氢氧化物作电解质,并掺入一定量的催化剂;石墨作阳极,不锈钢作阴极,加湿氧气作氧化剂。对不同的电解质、不同的氧气流量下DCFC的输出性能进行了试验研究。结果表明,KOH比NaOH的导电性好,电池运行更稳定,更有利于电池的输出;氧气流量为70mL/min时,该电池的输出性能最佳,最大电流密度、功率密度分别为105mA/cm2和0.041W/cm2,开路电压达到0.74V。电流密度为45mA/cm2时,输出电压0.65V,可连续稳定运行20h。提出了热解-直接碳燃料电池联合系统,并以C10H22为例,分析了联合系统发电效率高达76.5%,表明该系统在未来集中式电厂中有很好的应用前景。     

直接碳燃料电池性能研究

直接碳燃料电池(DCFC)勿需碳和氧气气化、重整,而直接通过电化学反应产生电能,效率可达80%,燃料的理论利用率可达100%,是一种高效、清洁的燃料电池.文章所介绍的组装DCFC单体电池,以石墨作阳极,不锈钢作阴极,加湿氧气作氧化剂,采用熔融氢氧化物作电解质,并掺入一定量的催化剂,该电池工作温度为500～700℃.对不同工作温度、不同电解质和不同氧气流量下DCFC的输出性能进行了试验研究.结果表明:随着工作温度的升高,电池输出性能有很大提高;KOH比NaOH的导电性好,电池运行更稳定,更有利于电池的输出;氧气流量为70mL/min,温度为650℃时,该电池的输出性能最佳,最大电流密度、功率密度分别为118mA/cm2和0.054 W/cm2,开路电压达到0.76 V.     

“双碳”目标下的北京市氢能应用场景研究

基于碳达峰碳中和宏观政策背景,分析研判了北京市碳达峰碳中和时间节点。结合氢能关键技术发展趋势,对北京市碳达峰、碳中和年度的氢能应用场景进行了分析,研究设计了基于氢燃料电池、氢能分布式发电、氢燃气轮机、氢能航空技术等核心技术的燃油机动车辆替代、燃气发电替代、天然气掺氢供热、居民用氢燃料电池等六大领域应用场景,提出了制定氢能中长期战略规划等政策建议。研究结果显示,氢能在北京市碳达峰年份的碳减排贡献度约为0.2%,在碳中和年份的碳减排贡献度约为10.29%,氢能将成为北京市产业及能源体系的重要组成部分。     

氢能发电技术的研究(Ⅰ)--铂碳复合电极材料对离子交换膜燃料电池放电性能的影响

离子交换膜燃料电池是氢能应用开发的重要研究领域.研究了离子交换膜燃料电池用的铂碳复合电极制备工艺和碳材料的选择对燃料电池电化学性能的影响.研究结果表明,铂碳复合电极的制备工艺对燃料电池放电性能有重要影响,采用刷涂法和物化法制备的铂碳复合电极所组装的燃料电池具有较好的电化学性能.研究结果还发现,复合电极中碳材料的微观结构也是影响燃料电池电化学性能的重要因素,碳材料的比表面积越大,燃料电池的放电性能就越好.     

基于碳平衡法的柴油车燃油消耗计算模型

本文阐述了碳平衡燃油消耗量分析法的基本原理;分析了澳大利亚、日本、美国、欧盟等柴油车油耗标准的碳平衡计算模型,其均未考虑柴油车排放颗粒物中的碳元素的存在.由于柴油的分子量大,而且柴油机为直接喷射,混合气不均匀,故部分燃料不能完全燃烧,在高温下分解为以碳为主的颗粒.当柴油车加速或者在车况差时,会产生更多的碳烟,在此基础上对柴油机油耗模型进行修正,对原公式考虑增加碳烟颗粒物的修正项,得出修正模型.分析认为,修正后的模型更合理,可提高计算精度.     

质子交换膜燃料电池专用碳纸的制备及性能测试

采用湿法造纸技术制备质子交换膜燃料电池电极扩散层专用碳纸材料,考察了影响专用碳纸性能的主要因素。研究结果表明：分散剂、粘合剂和纤维长度等对碳纸物性具有较大影响。以3M的NaOH处理碳纸的基体材料,控制打浆度20°SR,按比例加入自制功能性分散剂,在优化工艺条件下,制备的碳纸物性基本和日本东丽公司产品(Toray碳纸)物性相同。以自制的碳纸和Toray碳纸为电极扩散层基体材料组装成电池,放电性能测试表明,自制碳纸是一种较为理想的燃料电池电极扩散层基体材料。     

流化床电极直接碳燃料电池实验研究

将流化床电极应用到直接碳燃料电池(DCFC)中,得到一种新型的流化床电极直接碳燃料电池(FBEDCFC).为研究该燃料电池的输出特性,搭建了环形FBEDCFC实验装置,分析了反应温度、阴极气体流速、阳极气体流速、镍催化剂添加量和炭颗粒粒径对燃料电池放电曲线的影响.结果表明:反应温度为923K、阳极气体流速为18.59mm/s、阴极气体流速为19.57mm/s、镍催化剂添加量为45g、炭颗粒粒径为2.5~3.5mm时,可得到FBEDCFC的开路电压和最大输出功率密度,分别为0.896V和28.70mW/cm2.     

High efficiency chemical energy conversion system based on a methane catalytic decomposition reaction and two fuel cells: Part I. Process modeling and validation

A highly efficient integrated energy conversion system is built based on a methane catalytic decomposition reactor (MCDR) together with a direct carbon fuel cell (DCFC) and an internal reforming solid oxide fuel cell (IRSOFC). In the MCDR, methane is decomposed to pure carbon and hydrogen. Carbon is used as the fuel of DCFC to generate power and produce pure carbon dioxide. The hydrogen and unconverted methane are used as the fuel in the IRSOFC. A gas turbine cycle is also used to produce more power output from the thermal energy generated in the IRSOFC. The output performance and efficiency of both the DCFC and IRSOFC are investigated and compared by development of exact models of them. It is found that this system has a unique loading flexibility due to the good high-loading property of DCFC and the good low loading property of IRSOFC. The effects of temperature, pressure, current densities, and methane conversion on the performance of the fuel cells and the system are discussed. The CO₂ emission reduction is effective, up to 80%, can be reduced with the proposed system.     

Carbon anode in direct carbon fuel cell

Direct carbon fuel cell (DCFC) is a kind of high temperature fuel cell using carbon materials directly as anode. Electrochemical reactivity and surface property of carbon were taken into account in this paper. Four representative carbon samples were selected. The most suitable ratio of the ternary eutectic mixture Li₂CO₃–K₂CO₃–Al₂O₃ was determined at 1.05:1.2:1(mass ration). Conceptual analysis for electrochemical reactivity of carbon anode shows the importance of (1) reactive characteristics including lattice disorder, edge-carbon ratio and the number of short alkyl side chain of carbon material, which builds the prime foundation of the anodic half-cell reaction; (2) surface wetting ability, which assures the efficient contact of anode surface with electrolyte. It indicates that anode reaction rate and DCFC output can be notably improved if carbon are pre-dispersed into electrolyte before acting as anode, due to the straightway shift from cathode to anode for CO₃²⁻ provided by electrolyte soaked in carbon material.     

Enhancing triple-phase boundary at fuel electrode of direct carbon fuel cell using a fuel-filled ceria-coated porous anode

A new type of high-temperature fuel cell using solid carbon as a fuel, which is called a direct carbon fuel cell (DCFC), recently attracts scientific and industrial attention due to its excellent electrochemical efficiency, less production of CO₂, and no need of CO₂ separation. However, the state-of-the-art technology on the DCFC still stays in an idea developing stage, mainly because of fuel-related difficulties: a discontinuous fuel supply and a very limited formation of triple phase boundary. In this study, we focused on how to enhance the formation of triple phase boundary at the fuel electrode: using a porous Ni anode filled with carbon particles to enhance the fuel-electrode physical contact and making the porous anode wettable by ceria coating the anode. We demonstrated for the first time that the two ideas are quite successful, leading to 700% increase in a maximal power density and 500% increase in a maximal current density with respect to the standard case.     

Evaluation of raw coals as fuels for direct carbon fuel cells

As a promising high-temperature fuel cell, the direct carbon fuel cell (DCFC) has a much higher efficiency and lower emissions compared with conventional coal-fired power plants. In the present DCFC system, four Australian coals from Central Queensland are successfully tested at 600-800 °C. The electrochemical performances of these coals are highly dependent on their intrinsic properties, such as chemical composition, surface area, concentrations of oxygen-containing surface functional groups and the nature of mineral matter in their ashes. Impurities such as Al₂O₃ and SiO₂ lead to an inhibitive effect during the anodic reaction in the DCFC, while CaO, MgO and Fe₂O₃ exhibit a catalytic effect on the electrochemical oxidation of carbon.     

Effect of contact type between anode and carbonaceous fuels on direct carbon fuel cell reaction characteristics

The contact between the anode and the carbonaceous fuel has a strong effect on the direct carbon fuel cell (DCFC) reaction characteristics. These effects are experimentally investigated by measuring the electrochemical behavior of a detached anode, an anode in physical contact with the fuel and an anode with carbon deposited on the surface in a DCFC. The results show that for the detached type DCFC, the reaction characteristics are closely related to the anode gas. In an Ar atmosphere, the main anode reactions are the electrochemical reaction to produce O₂ and the carbon gasification with the formed O₂. In a CO₂ atmosphere, the main anode reactions are the carbon gasification with CO₂ and the electrochemical oxidization of the formed CO. For the physical contact type DCFC, the anode reaction mechanisms are the same as for the detached type DCFC with no electrochemical oxidization of carbon at the physical contact interface between the carbonaceous fuel and the anode. Thus, the increased contact does not result in better performance. The carbon-deposited type DCFC has better performance with a significant activation polarization due to the electrochemical oxidization of the deposited carbon.     

Integration of direct carbon fuel cells with concentrated solar power

In this paper, we will report on a study on the thermodynamic feasibility of a concept that realizes the cracking of methane with a concentrated solar power (CSP) reactor and electricity production with a direct carbon fuel cell (DCFC) and its possible contribution to a clean energy supply for Europe in the long-term future. The natural gas (methane) is decomposed in an endothermic reaction into hydrogen and carbon. The separated carbon is fed to a direct carbon fuel cell (DCFC) and converted with high efficiency to electric power. A model of the proposed concept is carried out in the flow sheet program Cycle-Tempo and the results of the simulations and the corresponding analysis are presented in this paper. Finally the location factors influencing the implementation of this concept in the north of Africa are evaluated.     

Electrochemical oxidation of graphite in an intermediate temperature direct carbon fuel cell based on two-phases electrolyte

As a promising intermediate temperature fuel cell, Direct Carbon Fuel Cell (DCFC) with composite electrolyte composed of Samarium-Doped Ceria (SDC) and a binary carbonate phase (67 mol% Li₂CO₃/33 mol% Na₂CO₃) has a much higher efficiency compared with conventional power suppliers. In the present work, SDC powder has been synthesized by an oxalate co-precipitation process and used as solid support matrix for the composite electrolyte. Single cell with composite electrolyte layer is fabricated by a dry-pressing technique using LiNiO₂/Li₂Na₂CO₃/SDC as cathode and 1:9 (weight ratio) graphite mixture with 67 mol% Li₂CO₃/33 mol% Na₂CO₃ molten carbonate as anode. The cell is tested at 600–750 °C using electrolytical graphite mixture as fuel and O₂/CO₂ mixture as oxidant. A relatively good performance with high power density of 58 mW cm⁻² at 700 °C is achieved for a DCFC using 0.8 mm thick composite electrolyte layer. The sensibility of the 1 cm² DCFC single cell performance to the anode gas nature is also investigated. At temperatures higher than 700 °C, both carbon (C) and carbon monoxide (CO) can be considered as reacting fuel for the DCFC system.     

Surface modification of carbon fuels for direct carbon fuel cells

The direct carbon fuel cell (DCFC) is a promising power-generation device that has much higher efficiency (80%) and less emissions than conventional coal-fired power plants. Two commercial carbons (activated carbon and carbon black) pre-treated with HNO₃, HCl or air plasma are tested in a DCFC. The correlation between the surface properties and electrochemical performance of the carbon fuels is explored. The HNO₃-treated carbon fuels have the highest electrochemical reactivity in the DCFC due to the largest degree of surface oxygen functional groups. The overall effect on changing the electrochemical reactivity of carbon fuels is in the order HNO₃ > air plasma ≈ HCl. Product gas analysis indicates that complete oxidation of carbon to CO₂ can be achieved at 600–700 °C.     

A novel direct carbon fuel cell by approach of tubular solid oxide fuel cells

A direct carbon fuel cell based on a conventional anode-supported tubular solid oxide fuel cell, which consisted of a NiO-YSZ anode support tube, a NiO-ScSZ anode functional layer, a ScSZ electrolyte film, and a LSM-ScSZ cathode, has been successfully achieved. It used the carbon black as fuel and oxygen as the oxidant, and a preliminary examination of the DCFC has been carried out. The cell generated an acceptable performance with the maximum power densities of 104, 75, and 47 mW cm⁻² at 850, 800, and 750 °C, respectively. These results demonstrate the feasibility for carbon directly converting to electricity in tubular solid oxide fuel cells.