On the other hand, if evolved gas bubbles have similar or larger size than that of the pores, we should consider the force balance between the buoyancy effect (Fb) and the bubble-catalyst interface surface tension force (Fs), Fb (=ΔρVg) ~ Fs ð¼ γ‘Þ, where Δρ is the density difference between gas and liquid, g is the gravitational acceleration, γ is the surface tension, and ‘ is the perimeter length for the gas–liquid wetting.