Ultra-stable porous yolk-shell Ni catalysts for the steam reforming of methane with alkali poisoning

•Ni/pys-Al2O3 exhibited the highest performance in the SRM with alkali poisoning.•TOF is dependent on Ni size and increases below 50 nm of Ni size.•Porosity and Ni size are maintained after the reaction and alkali poisoning.•Porous yolk-shell is effective in preventing the sintering and alkali poisoning.•Yolk-shell catalysts showed less carbon formation than Ni/commercial catalyst.