Cell-protecting regeneration from anode carbon deposition using in situ produced oxygen and steam: A combined experimental and theoretical study

Carbon deposition is a primary concern during the operation of solid oxide fuel cells (SOFCs) fueled with hydrocarbon fuels, leading to cell degradation and even cell damage. Carbon elimination is expected to be a promising approach to prolong cell life. This work reports on a combined experimental and theoretical investigation of cell regeneration from anode carbon deposition of tubular SOFCs fabricated by phase-inversion and co-sintering techniques. The as-prepared cell exhibits a maximum power density of 0.20 W cm−2 at 800 °C fueling with wet CH4, but fails to stable operation due to severe carbon deposition. Based on thermodynamic predictions, a successive cell-protecting regeneration process is proposed to eliminate deposited carbon without oxidizing Ni catalysts, during which CH4 and H2 fuels are provided in circulation. Through a total of 35 cycling tests, cell performance can always successfully restore to the initial level. The possible carbon elimination mechanism is investigated in detail based on thermodynamic and first-principle calculations. The feasibility of carbon elimination using in situ produced oxygen or steam through electrochemical reaction has been revealed, providing a novel continuous operation mode for hydrocarbon-based SOFCs.