Enhancing coking resistance of Ni/YSZ electrodes: In situ characterization, mechanism research, and surface engineering

Highlights: • Advanced in situ characterization techniques for studying coking reactions. • Fundamentals of coking, including mechanisms, thermodynamics and kinetics. • Various novel engineering approaches for enhanced coking self-resistance. • Challenges, future outlook and perspectives on anti-carbon research of SOFC. • Applicability to diverse material systems that suffer from coking degradation. -- Abstract: Owing to their high efficiency and low emission, solid oxide fuel cells (SOFCs) are promising devices that directly convert various hydrocarbon fuels into electric power and chemical materials through catalytic oxidation. However, the broad and large-scale implementation of the technology is hindered by anode coking, which distinctively weakens electrochemical catalytic oxidation in anodes and causes serious passivation issues and even the failure of SOFC systems. Since surface coke can occur in a few seconds and within several nanometers of an anode surface, advanced in situ characterization methods and theoretical simulations are crucial to provide valuable insight into the evolution of surface structures and compositions in real time and at high spatial and temporal resolutions in this dynamic process. In this review, we highlighted the recent progress in the fundamental understanding of anode coking and considered the elementary steps, thermodynamics, kinetics and susceptible sites of coking. We also reviewed representative surface engineering approaches that enhance electrode durability under carbon-related atmospheres. Furthermore, the knowledge and methodology introduced in this paper are applicable to industrial operations, which often encounter carbon poisoning issues, including steam reforming of natural gas, styrene production from ethylbenzene, cracking reaction of heavy oil fractions, and solid acid alkylation.