Efficient and stable conversion of oxygen-bearing low-concentration coal mine methane by the electrochemical catalysis of SOFC anode: From pollutant to clean energy

Large quantity of low-concentration coal mine methane (LC-CMM) has been directly emitted to the air, causing severe greenhouse effect and energy loss. We propose to convert the pollutant gas to clean energy by the anodic electrochemical catalysis of solid oxide fuel cells. In the electrochemical conversion of oxygen-bearing LC-CMM, the Ni-based anode shows high catalytic activity and good stability without severe carbon deposition, Ni oxidation or thermal runaway. High electrochemical performance and good discharging stability were achieved with very flexible O-2/CH4 ratio and low CH4 concentration. The high electric efficiency of 38.2 % with the fuel utilization of 72 % and the stable discharging for 400 h can be realized by the stacks using the LC-CMM. Accordingly, a heterogeneous kinetics and electrochemical charge-transfer model was established to study the elementary reaction mechanism of O-2 in CH4 conversion and carbon removing, also showing the theoretical thresholds of coking and Ni oxidation.