*2.3. Catalyst Characterization*

A spectroscopic ellipsometer J.A. Woollam M-2000UI (J.A. Woollam Co., Lincoln, NE, USA) was used to determine the catalytic film thickness. This was obtained by using a Cauchy model for fitting.

The surface topography of the catalytic thin films was evaluated with field emission scanning electron microscopy (FESEM) Hitachi S-4800 (Hitachi, Tokyo, Japan). An atomic force microscopy (AFM) (Park NX10, Park Systems, Suwon, Korea) was utilized for analysing the film morphological properties such as roughness and cluster size. All measurements were done in non-contact mode with a cantilever force constant of 42 N/m.

The crystal structure of the catalytic materials was studied by a Rigaku SmartLab® Type F XRD (Rigaku, Tokyo, Japan; Cu-Kα radiation, λ = 1.5418 Å). The grazing incidence X-ray diffraction (GIXRD) scan was collected with a grazing incidence angle of 0.5◦. Scan speed of 0.9◦/min and 2θ values from 20◦ to 90◦ were used. The high resolution scan was taken with speed 0.045◦/min.

The surface chemical composition, bonding properties and analysis of impurities in the deposited films were investigated by X-ray photoelectron spectroscopy (XPS) using an ESCALAB 250Xi (Thermo Scientific, Loughborough, UK) with a monochromated Al-Kα (energy of 1486.7 eV) X-ray source in the constant pass energy mode with a value of 50 eV. For high resolution spectra of Ag 3*d* a pass energy of 20 eV with resolution 0.1 eV was used. Charging compensation by an electron flood source was used in all measurements to minimize binding energy shifts. The binding energy of C 1*s* was set to be 284.5 eV as an internal standard for calibration. Sputtering by Ar<sup>+</sup> ions at 2 kV for 20 s was applied to remove surface contaminations and obtain actual carbon levels in the films. Deconvolution and fitting of the obtained peaks were made with Avantage software (Version 5.938) using Smart type background and applying 90:10 Gaussian-Lorentzian peaks.
