Water-gas shift (WGS) reactions on Co3O4 nanorods and Co3O4 nanorods anchoring singly dispersed Pt atoms were explored through building correlation of catalytic performance to surface chemistry of catalysts during catalysis using X-ray absorption spectroscopy, ambient pressure X-ray photo-electron spectroscopy (AP-XPS), and environmental TEM. The active phase of pure Co3O4 during WGS is nonstoichiometric cobalt monoxide with about 20% oxygen vacancies, CoO0.80. The apparent activation energy (E-2) in the temperature range of 180-240 degrees C is 91.0 +/- 10.5 kJ mol(-1). Co3O4 nanorods anchoring Pt atoms (Pt/Co3O4) are active for WGS with a low E-a of 50.1 +/- 50. kJ mol(-1) in the temperature range of 150-200 degrees C. The active surface of this catalyst is singly dispersed PtiCon nanoclusters anchored on Co3O4 (Pt-i/Co3O4), evidenced by in situ studies of extended X-ray absorption fine structure spectroscopy. In the temperature range of 200-300 degrees C, catalytic in situ studies suggested the formation of PtmCom' nanoclusters along with the reduction of Co3O4 substrate to CoO1-x. The new catalyst, PtmCom'/CoO1-x is active for WGS with a very low E-a of 24.8 +/- 3.1 kJ mol(-1) in the temperature range of 300-350 degrees C. The high activity could result from a synergy of PtmCom' nanoclusters and surface oxygen vacancies of CoO1-x.