熔融碳酸盐电解用铁镍基金属析氧阳极研究

Molten carbonate electrolysis （MCE） is a newly developing technology of green metallurgy and carbon dioxide utilization. Up till now, the researches are more focusing on the cathode processes and cathode products, very few research on anode. Our previous work have shown that nickel and nickel-iron based alloy anode had anomalous temperature effect in a molten carbonate electrolysis cell. Under practical operation conditions, the anode will work under a more severous situation with aggressive ions such as trace sulphate and alternating atmosphere. In this project, we propose to study cost-affordable ferronickel alloy based inert anode using a variety of electrochemical techniques, combined with chemical analysis and morphology observation and structure characterization. The relationship between the structural and functional stability of the anode and the composition and structure of the surface scale and metal anode oxidation condition is the central science of the project. A systematical investigation on the effects of material composition and initial surface condition, the composition of the molten salt with different temperatures and atmospheres, the electrochemical polarization conditions on the composition and structure of surface film and its stability and catalytic activity for oxygen evolution will be carried out. The robust mechanism and working condition that the iron and nickel based metallic anode can suffer from the sulfate corrosion, temperature fluctuation and the atmosphere change will be evaluated and identified. The research achievement will lead to a guidance for developing practical inert anode for the novel molten carbonate electrolysis technologies.

熔融碳酸盐电解（MCE）是新近发展起来的一项绿色冶金与二氧化碳高附加值资源化利用新技术，过去多集中在较单一条件下阴极过程和阴极产物研究，对阳极特别是多因素变化的复杂条件下的阳极材料研究甚少。项目组前期研究表明镍及镍基合金作为MCE阳极时存在反常温度效应，环境气氛变化与体系中微量硫酸盐等侵蚀性离子显著影响阳极稳定性。本项目提出研究铁镍基非贵金属不溶性析氧阳极，采用多种电化学技术，结合化学分析和形貌观察与结构表征及光谱分析等手段，围绕“金属熔盐电化学氧化—表面膜组成结构—析氧性能与稳定性“关系的核心科学问题，系统考察和深入认识材料组成与初始表面状态、熔盐成分与温度、环境气氛、极化条件等对表面膜组成与结构及其稳定性和析氧催化活性的影响规律，探明镍铁基金属析氧阳极抗少量硫酸盐侵蚀、耐温度涨落与气氛变化的条件与机制，为发展熔融碳酸盐电解新技术所需的适应苛刻条件的可实用化阳极提供科学技术基础。

熔融碳酸盐电解可望利用可再生能源电力实现绿色冶金和二氧化碳捕集与资源化利用，是具有重要应用前景的减碳和负碳技术，其中能满足实用需求的析氧阳极是制约该技术发展的瓶颈材料。本项目在过去研究的基础上，采用电化学技术和多种材料表征手段系统研究了铁镍基材料用于熔融碳酸盐电解体系惰性析氧阳极的可行性、服役工况和电解液中侵蚀性离子对阳极稳定性的影响规律和提高提高铁镍基阳极服役稳定性的方法。实验在考察不同组成的 Fe基合金在三元碳酸盐中的阳极氧化行为、成膜动力学和氧化膜结构组成结构的基础上，优选了FeNi36的合金组成。获得了环境气氛对镍基合金阳极稳定性的影响规律和机制，明确了侵蚀性氯离子和硫酸根离子对Ni-Fe基阳极服役稳定性的影响规律及机制，确定了临界侵蚀性离子浓度条件。建立了Ni-Fe基阳极表面氧化膜溶解度和熔盐酸碱度之间的关系，并基于溶解-沉积模型解释了Ni-Fe基阳极在气-液-固三相界线区域的加速腐蚀机制。在上述研究基础上，提出了调控电解液碱度以提高Ni-Fe基阳极低温耐蚀性的思路，实现了Ni-Fe基阳极在低温（＜500°C）熔融碳酸盐体系中长时间稳定服役。研究结果为发展熔融碳酸盐电解低成本高稳定析氧阳极提供了理论参考，开发出了可实用的铁镍基惰性阳极并在千安级电解槽中进行了长时间电解的初步应用验证。