and Curtis P. Berlinguette.*,, Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T1Z1.

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1 Supplementary Materials for Photodecomposition of metal nitrate and chloride compounds yields amorphous metal oxide films Jingfu He, David M. Weekes, Wei Cheng, Kevan E. Dettelbach, Aoxue Huang, Tengfei Li, and Curtis P. Berlinguette.*,, Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T1Z1. Department of Chemical & Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, BC V6T1Z3. Stewart Blusson Quantum Matter Institute, The University of British Columbia, 2355 East Mall, Vancouver, BC V6T1Z4. * Correspondence to: cberling@chem.ubc.ca. S0

2 Materials and Methods: Materials. Iron(III) chloride (98%) anhydrous (FeCl 3 ) and copper(ii) chloride (CuCl 2 ) were purchased from Aldrich; cobalt(ii) nitrate hexahydrate [Co(NO 3 ) 2 6H 2 O], iron(iii) nitrate nonahydrate [Fe(NO 3 ) 3 9H 2 O], cobalt (II) chloride anhydrous (CoCl 2 ), nickel(ii) nitrate hexahydrate [Ni(NO 3 ) 2 6H 2 O], and nickel(ii) chloride hexahydrate (NiCl 2 6H 2 O) were purchased from Fischer Scientific; zinc(ii) chloride (ZnCl 2 ), zinc(ii) nitrate hexahydrate [Zn(NO 3 ) 2 6H 2 O], copper(ii) nitrate trihydrate [Cu(NO 3 ) 2 3H 2 O] and iron (III) 2-ethylhexanoate (Fe(eh) 3 ) were purchased from Strem. All reagents were used without further purification. Fluorine-doped tin oxide coated glass (FTO) was purchased from Hartfort Glass Co., and indium tin oxide coated polyethylene terephthalate (PET-ITO) substrate was purchased from Aldrich. The sheet resistance of the PET-ITO was 60 Ω/aq. Film syntheses. All inorganic metal compound precursors were dissolved in water to form 1 M precursor solutions. Fe(eh) 3 was dissolved in hexanes to form a 0.3 M precursor solution. The solutions were spin-cast onto FTO (or PET-ITO plastic) at 3000 rpm for 1 min. The blank FTO (or PET- ITO plastic) was exposed to UV light for 10 min prior to deposition. The resultant films were left under a non-coherent UV lamp for 2-16 h (Model#: GPH436T5VH, Atlantic Ultraviolet Co.; max ~ 254 nm and 185 nm; flux = 0.12 mw/cm 2 at 1 m from lamp, ~10 mw/cm 2 at 5.5 cm in our experiment). In our experiments, all samples are placed 5.5 cm below the light source. More information of the radiation spectra can be obtained from the website: S1

3 Physical Characterization. X-ray photoelectron spectroscopy (XPS) analyses were carried out on a Leybold MAX200 spectrometer using Al Kα radiation. The pass energy used for the survey scan was 192 ev, whereas for the narrow scan it was 48 ev. X-ray diffraction (XRD) patterns were recorded on a Bruker D8-Advance X-ray diffractometer operating in reflection mode and equipped with Cu Kα radiation (40 kv, 40 ma). Scanning electron microscope (SEM) images were acquired on a FEI Helios NanoLab 650 dual beam SEM. X-ray fluorescence measurements were taken with a Thermo Fisher Scientific Niton XL3t analyzer utilizing a shielded test stand. The X-ray source was run with an accelerating voltage of 50 kv and a current of 40 µa. Scan time was 60 s for each sample. Fourier transform infrared (FTIR) spectroscopy analyses were performed on a Bruker alpha spectrometer with a transmission accessory. UV-vis absorption spectroscopy analyses were performed on a PerkinElmer Lambda 35 UV-Vis spectrophotometer. Electrochemical measurements were performed on a CH Instruments Workstation 660D potentiostat. The electrochemical measurements of all amorphous metal oxide samples were carried out in 1 M KOH. The test cell was a single compartment, three-electrode cell made from a plastic beaker. We used an Ag/AgCl reference electrode (CH Instruments) and a Pt wire counter electrode. The Ag/AgCl electrode was calibrated against a reversible hydrogen electrode (RHE) using a Pt electrode for both the working and counter electrodes in the same 1 M KOH electrolyte sparged with H 2 (Praxair). Samples that were to be studied by electrochemical means were deposited onto 3 3 cm FTO coated glass (or ITO-PET). The samples were each broken into three 1 3 cm pieces with the centre piece being used for all subsequent electrochemical studies. The sample was then tightly wrapped with Teflon tape to expose a 1 cm 2 working area. The resistances for all samples were measured and deducted for amorphous metal oxides on FTO S2

4 glass. The resistances for samples on ITO-PET were also measured as 108 and 120 Ω for FeO nitrate and Fe 0.2 Ni 0.8 O nitrate, but not deducted because the current curve would be deformed severely. Cyclic voltammograms were performed for all samples at scan rates of 10 mv s -1. Tafel slopes were determined by measuring current density at different potentials. The current density values was recorded at 180 s after the start of each voltage. Figure S1. Normalized chlorine XRF signal as a function of time during the exposure of films of MCl x to UV light. S3

5 Figure S2. FTIR spectra of a Fe(NO 3 ) 3 film as a function of photolysis time showing the progressive disappearance of nitrate signals under (a) ambient atmosphere (no ozone produced) and (b) N 2 atmosphere. S4

6 Figure S3. (a) UV-vis spectra for Fe(NO 3 ) 3 precursor thin films (red) and FeO nitrate after photolysis (blue). (b) UV-vis spectra for FeCl 3 precursor thin films (red) and FeO chloride after photolysis (blue). Traces for blank FTO and samples annealed at 600 C are displayed for reference. S5

7 Figure S4. FTIR spectra showing the complete disappearance of nitrate and H-O signals during the photodecomposition of (a) Ni(NO 3 ) 3 and (b) Fe/Ni(NO 3 ) x spin-coated on FTO. Insets: XRF spectrum for (a) NiO chloride film and (b) Fe 0.2 Ni 0.8 O chloride film. Element distribution mapping of (c) Fe and (d) Ni for a Fe 0.2 Ni 0.8 O nitrate sample. S6

8 Figure S5. FTIR spectra showing the time-dependent disappearance of nitrate signals during the photodecomposition of (a) CoO nitrate, (b) NiO nitrate, (c) CuO nitrate, and (d) ZnO nitrate films on FTO. S7

9 Figure S6. Chronopotentiometric data recorded for FeO nitrate and Fe 0.2 Ni 0.8 O nitrate at a constant current density of 10 ma/cm 2. The results show only a small increase in overpotential of ~25 mv for the Fe 0.2 Ni 0.8 O nitrate film over the course of the experiment. S8