Fig. 2: Characterization results of catalysts.

a XRD patterns of the as-prepared (blue line), calcined (black line), and reduced (red line) 15wt.%MoO3/ZnO catalysts. b Normalized XANES spectra at the K-edge of Mo of the 15wt.%MoO3/ZnO catalyst and three reference compounds (ZnMoO4, MoO3, and AHM). c Normalized XANES spectra at the K-edge of Mo of the reduced MoO3, 15wt.%MoO3/ZnO catalyst and two reference compounds (MoO3 and MoO2). d STEM image and elemental mappings of the reduced 15wt.%MoO3/ZnO catalyst. e TG profiles of the reduced MoO3 and 15wt.%MoO3/ZnO catalysts in flowing air. f Mo 3d core level XPS spectrum of the reduced MoO3 and 15wt.%MoO3/ZnO catalysts. 15wt.%MoO3/ZnO represents that the mass of Mo element in the catalyst accounts for 15% of the total mass.