CuOx/SiO2　precursor　was　successfully　fabricated　by　an　ammonia　evaporation　hydrothermal　method.　Upon　reduction　in　5　vol　%　H2/N2　at　250,　300,　350,　400,　or　450　°C,　CuO　and　copper　phyllosilicate　species　in　the　precursor　bring　about　the　formation　of　highly　dispersed　Cu0　and　Cu+　species,　respectively.　The　Cu+/Cu0　ratios　were　studied　by　XAES　technique,　while　the　particle　sizes　were　estimated　on　the　basis　of　HRTEM　images.　It　is　disclosed　that　the　ratios　and　particle　sizes　varied　with　CuOx/SiO2　reduction　temperatures.　The　results　of　in　situ　DRIFTS　and　XAES　characterization　reveal　that　both　Cu0　and　Cu+　are　active　for　CO　adsorption　and　water　dissociation,　especially　so　with　Cu0　and　Cu+　particles　of　small　sizes.　It　was　also　observed　that　the　adsorption　of　CO　on　Cu+　is　stronger　than　that　on　Cu0,　and　Cu0　is　more　active　than　Cu+　for　water　dissociation.　Among　the　prepared　Cu/SiO2　catalysts,　the　one　resulted　from　precursor　reduction　at　300　°C　shows　the　highest　CO　conversion　in　WGS　reaction,　which　is　attributed　to　the　small　size　of　Cu0　(2.45　nm)　and　the　large　amount　of　Cu+.　©　2020　Wiley-VCH　GmbH