Combining silica to boost the ammonia synthesis activity of ceria-supported Ru catalyst

•Silanol groups in Ru/Ce-Si lead to enhance the amount of Ru species surrounded by oxygen atoms.•Ceria-supported Ru catalyst with SiO2 adsorbs a larger amount of hydrogen species.•The addition of SiO2 accelerates the desorption and exchange of hydrogen species.•SiO2 doping increases ammonia synthesis activity by more than 34% and reduces activation energy.