Supporting Information

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1 Supporting Information Identification of the nearby hydroxyls role in promoting HCHO oxidation over a Pt catalyst Ying Huo #, Xuyu Wang #, Zebao Rui *, Xiaoqing Yang, Hongbing Ji * School of Chemical Engineering and Technology (Zhuhai ), Fine Chemical Research Institute, School of Chemistry (Guangzhou ), Sun Yat-sen University, P.R. China # Equal contribution *Correspondence to the authors can be sent to Z. B. Rui (ruizebao@mail.sysu.edu.cn ) and H. B. Ji (jihb@mail.sysu.edu.cn ) S1

2 Table of Contents Experimental details Figures Figure1S1. Optimized configurations of Pt (111) supported an M atom (denoted as PtM) and a hydroxyl adsorption over PtM, M= Mn, Fe, Co and Ni Figure S2. TEM images of PtM/Al 2 O 3 (M = Mn, Fe, Co, Ni) Figure S3. Al 2p XPS spectra of Pt/Al 2 O 3 and PtM/Al 2 O 3 (M = Mn, Fe, Co, Ni) Figure1S4. Pt 4d XPS spectra of (a) Pt/Al 2 O 3, (b) PtMn/Al 2 O 3, (c) PtFe/Al 2 O 3, (d) PtCo/Al 2 O 3 and (e) PtNi/Al 2 O 3 Figure S5. M 2p XPS spectra of (a) PtMn/Al 2 O 3, (b) PtFe/Al 2 O 3, (c) PtCo/Al 2 O 3 and (d) PtNi/Al 2 O 3 (M = Mn, Fe, Co, Ni) Figure1S6. FTIR spectra of PtCo/Al 2 O 3 upon on-stream treatment at varies humidity conditions Figure1S7. The effluent CO 2 flux as a function of time during the in situ DRIFTS experiments over PtMn/Al 2 O 3, PtFe/Al 2 O 3, PtCo/Al 2 O 3 and PtNi/Al 2 O 3 at various temperatures Figure1S8. (a) Intensity of 1570 cm 1 peak vs. time during O 2 + HCHO + He gas mixture adsorption at 30 o C and (b) intensity of 1570 cm 1 peak vs. temperature during O 2 + HCHO + He gas mixture adsorption for 60 min Figure S9. Optimized structures of reactant, transition, and product states and energy changes (in ev) for formate-oh reaction step (CHO 2 + OH CO 2 + H 2 O) over PtM(OH) (M= Mn, Fe, Co, Ni). The loden circle is Pt atom, the purple ones refer to M atoms, the blue ball is carbon, the white ones correspond to H atoms and the red ones are O atoms. S2

3 Experimental Details Catalysts characterization Transmission electron microscopy (TEM, FEI Tecnai G2 Spirit) was used for the observation of nanoparticles and their size distribution. High-angle annular dark-field (HAADF) imaging in the scanning transmission electron microscopy (STEM) mode was performed on the same electron microscope tilting the sample about a single axis using a Fischione ultra-narrow gap tomography holder. The phase purity and crystal structure of the catalysts were examined by X-ray diffraction (XRD, D-MAX 2200 VPC) using monochromatic CuKa radiation. BET surface area, pore size and pore volume of the samples were determined by N 2 adsorption isotherms at -196 C on ASAP 2020 adsorption equipment. Before N 2 adsorption experiment, the sample was degassed at 200 C for 3 h under vacuum. CO chemisorption analysis was performed at 35 C using a Micromeritics ASAP 2020C automated system. Before CO chemisorption, the sample was first evacuated at 10-6 mm Hg and 110 C for 30 min followed by the reduction under flowing H 2 at 200 C for 30 min. A CO/Pt average stoichiometry of 1 was assumed for the dispersion calculation. X-ray photoelectron spectroscopy (XPS) analysis was conducted on a ESCALAB 250 spectrometer (Thermo Fisher Scientific, Al Kα monochromate, hν = ev) under a vacuum of Pa. Charging effects were corrected by adjusting the main C 1s peak to a position of ev. Fourier transform infrared spectra (FTIR) were collected using a Bruker Tensor 37 FTIR Spectrometer in the frequency range of cm -1. About 1 mg of sample was mixed in an agate mortar with 300 mg of Perkin Elmer s potassium bromide followed by a thorough drying under a heat lamp. The mixture was then pressed into a pellet die for 5 min using a force of 5 tons, and transparent pellets were obtained for FTIR tests. In situ Diffuse Reflectance Infrared Fourier Transformed Spectroscopy (DRIFTS) analysis used in this study was performed on EQVINOX-55 FFT spectroscope apparatus (Bruker), equipped with a diffuse reflectance accessory and a Mercury Cadmium Telluride (MCT) detector. About 10 mg finely ground sample was packed in the ceramic crucible of the in situ chamber. 100 ml/min He or reactant stream (He/O 2 = 4) containing HCHO and water vapor ( 35% relative humidity) was introduced. The spectra under reaction conditions were recorded after 64 scans with a resolution of 4 cm -1.The in situ DRIFT spectrum in He flow at room temperature was measured and taken as a background for each sample. S3

4 The effluent species were monitored with a mass spectrometry (MS; Hidden HPR 20) to monitor CO 2 at m/e = 44. HCHO catalytic oxidation A quartz tubular (i.d.=7 mm) fixed-bed reactor was used for the catalytic oxidation of HCHO under atmospheric pressure. Approximately 0.2 g of the catalyst with particle size of 177~250 µm was packed. The reactant is composed of a simulated air stream (N 2 /O 2 =4, 80 ml/min), ~30 ppm HCHO and water vapor (~35% relative humidity or RH). Gaseous HCHO was generated by passing a stream of simulated air through a bubbler containing a HCHO solution (35 wt.% HCHO). Experiments were performed at GHSV (gas hourly space velocity) of ml h -1 g -1. In the case of dry reaction experiment (< 5% RH), the reactant was treated by a CaCl 2 fixed bed before entering the reactor. HCHO concentration in the reactant or product gas stream was analyzed by phenol spectrophotometric method 1. The conversion of HCHO was calculated based on the concentration change. Reference (1) Chen, H.; Rui, Z.; Ji, H., Monolith-like TiO 2 nanotube array supported Pt catalyst for HCHO removal under mild conditions. Ind. Eng. Chem. Res. 2014, 53, S4

5 Figures Figure S1. Optimized configurations of Pt (111) supported an M atom (denoted as PtM) and a hydroxyl adsorption over PtM, M= Mn, Fe, Co and Ni. S5

6 Figure S2. TEM images of PtM/Al 2 O 3 (M = Mn, Fe, Co, Ni) S6

7 Figure S3. Al 2p XPS spectra of Pt/Al 2 O 3 and PtM/Al 2 O 3 (M = Mn, Fe, Co, Ni) S7

8 Figure S4. Pt 4d XPS spectra of (a) Pt/Al 2 O 3, (b) PtMn/Al 2 O 3, (c) PtFe/Al 2 O 3, (d) PtCo/Al 2 O 3 and (e) PtNi/Al 2 O 3 S8

9 Intensity (a.u.) (a) Mn 2p PtMn/Al2O Binding Energy (ev) Intensity (a.u.) (b) Fe 2p PtFe/Al2O Binding Energy (ev) Intensity (a.u.) (c) Co 2p PtCo/Al2O Binding Energy (ev) Intensity (a.u.) (d) Ni 2p PtNi/Al2O Binding Energy (ev) Figure S5. M 2p XPS spectra of (a) PtMn/Al 2 O 3, (b) PtFe/Al 2 O 3, (c) PtCo/Al 2 O 3 and (d) PtNi/Al 2 O 3 (M = Mn, Fe, Co, Ni) S9

10 Transmittance (a.u.) PtCo/Al2O3 Fresh sample Stage 1(after treatment at RH < 5%) Stage 2 (revovered of Stage 1 at RH ~ 35%) Wavelength (cm -1 ) Figure S6. FTIR spectra of PtCo/Al 2 O 3 upon on-stream treatment at varies humidity conditions S10

11 Figure S7. The effluent CO 2 flux as a function of time during the in situ DRIFTS experiments over PtMn/Al 2 O 3, PtFe/Al 2 O 3, PtCo/Al 2 O 3 and PtNi/Al 2 O 3 at various temperatures S11

12 Integrated Area (a) PtMn/Al2O3 PtFe/Al2O3 PtCo/Al2O3 PtNi/Al2O3 Integrated Area (b) PtMn/Al2O3 PtFe/Al2O3 PtCo/Al2O3 PtNi/Al2O Time (min) Temperature ( o C) Figure S8. (a) Intensity of 1570 cm 1 peak vs. time during O 2 + HCHO + He gas mixture adsorption at 30 o C and (b) intensity of 1570 cm 1 peak vs. temperature during O 2 + HCHO + He gas mixture adsorption for 60 min S12

13 Figure S9. Optimized structures of reactant, transition, and product states and energy changes (in ev) for formate-oh reaction step (CHO 2 + OH CO 2 + H 2 O) over PtM(OH) (M= Mn, Fe, Co, Ni). The loden circle is Pt atom, the purple ones refer to M atoms, the blue ball is carbon, the white ones correspond to H atoms and the red ones are O atoms. S13