Fig. 3
In-situ XANES of 1.0 wt% Au/CeO2&AC catalyst and relative fitting values. a The in situ XANES spectra of Au L3 edges as a function of reaction time and b the relative linear combination fitting analysis with the fitting errors. c The in situ XANES spectra of Ce L3 edges as a function of reaction time and d the relative multiple peak fitting analysis with the fitting errors. To minimise the conceivable influence by acetylene adsorption and the changes in metal speciation geometry in XANES spectra fitting, the higher ratio of HCl/C2H2 = 2: 1 (Fig. 1e). Au standards of 1.1 Au(III) (e.g. [AuCl4]−), 0.7 and 1.0 Au(I) (e.g. [AuCl2]− and AuCl), and Au(0) foil, Ce standards of 1.8 Ce(IV) and 2.6 Ce(III) are used for fitting the typical normalized white-line intensity values (Supplementary Figure 6). The details of the fitting are described in supporting information. Before introducing the reactants into micro-reactor, the fresh Au/CeO2&AC catalyst was heated to 180 °C in N2 gas for 30 min. The colour indicates the difference in the white-line intensity: from 0 to 0.5 to >1 (blue to yellow to red) for Au, 0 to 0.8 to >1.5 (blue to yellow to red) for Ce
