CO x co-methanation over coal combustion fly ash supported Ni-Re bimetallic catalyst: Transformation from hazardous to high value-added products.

•Hazardous coal combustion fly ash was utilized as low-cost catalyst support.•The supported Ni-Re bimetallic catalyst was prepared by a facile method.•The catalytic COx co-methanation performance was enhanced due to Re addition.•The optimal addition amount of Re promoter was 1.0 wt%.•The reaction pathway of CO and CO2 differs from the first step of adsorption.