Ni and Rh on La2O3–CeO2–ZrO2 low temperature CH4 steam reforming kinetics studied. Kinetic isotope effects during CH4 steam reforming and decomposition measured. CH bond activation kinetically limiting over Ni and Rh with no steam participation. Microkinetic modelling identifies CH3* dehydrogenation as the rate determining step. Binding energies of key surface species help discriminate catalysts’ performance.