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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 photoelectron spectroscopy(AP-XPS),and environmental TEM.The active phase of pure Co3O4 during WGS is nonstoichiometric cobalt monoxide with about 20%oxygen vacancies,CoO 0.80.The apparent activation energy(Ea)in the temperature range of 180–240℃ is 91.0±10.5 kJ mol–1.Co3O4 nanorods anchoring Pt atoms(Pt/Co 3 O 4)are active for WGS with a low Ea of 50.1±5.0 kJ mol–1 in the temperature range of 150–200 ℃.The active surface of this catalyst is singly dispersed Pt1Con nanoclusters anchored on Co3O4(Pt1/Co3O4),evidenced by in situ studies of extended X-ray absorption fine structure spectroscopy.In the temperature range of 200–300℃,catalytic in situ studies suggested the formation of PtmCom′ nanoclusters along with the reduction of Co3O4 substrate to CoO1-x.The new catalyst,PtmCom′/CoO 1-x is active for WGS with a very low Ea of 24.8±3.1 kJ mol–1 in the temperature range of 300–350℃.The high activity could result from a synergy of PtmCom′ nanoclusters and surface oxygen vacancies of CoO1–x.