NiO Dissolution in Molten Carbonate Fuel Cell Cathodes: Challenges and Strategies for Long-Term Stability

Molten carbonate fuel cells (MCFCs) are highly promising for efficient electricity generation and selective CO2 capture, particularly in hard-to-abate sectors such as maritime and heavy industry. However, their operational lifetime is constrained by the dissolution of nickel oxide (NiO) cathodes in molten carbonate electrolytes, which leads to voltage degradation and potential short-circuiting. This review evaluates strategies to enhance cathode stability and reduce NiO solubility. Key approaches include advanced coatings (LiCoO2, TiO2, ZrO2, and Co3O4), doping, partial replacement with alternative materials (LiFeO2, La-based oxides, and bismuth-yttrium-samarium oxide [BYS]), and electrolyte modification using alkaline and rare-earth oxides. Various fabrication techniques, including sol-gel, Pechini, atomic layer deposition (ALD), tape-casting, and slurry infiltration, were applied to produce uniform, adherent, and chemically stable cathode layers. Reported studies show that optimized coatings and dopants can reduce NiO dissolution by 50%-60%, enhance electronic conductivity, and improve structural stability under prolonged operation. Multilayer cathode architectures and modified electrolytes further improve oxygen reduction kinetics, mechanical robustness, and power density. Collectively, these strategies significantly extend MCFC lifetime and performance, offering a pathway toward cost-effective, durable, and high-performance cells. The findings underscore the critical role of integrating material innovations and electrolyte engineering to advance MCFC commercialization while simultaneously supporting CO2 mitigation.