Supporting Information: Mechanistic Study of Gas-Phase Controlled Synthesis of. Copper Oxide-Based Hybrid Nanoparticle for CO Oxidation

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1 Supporting Information: Mechanistic Study of Gas-Phase Controlled Synthesis of Copper Oxide-Based Hybrid Nanoparticle for CO Oxidation Fu-Cheng Lee, Yi-Fu Lu, Fang-Chun Chou, Chung-Fu Cheng, Rong-Ming Ho, De- Hao Tsai * Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, R.O.C. * Corresponding author. dhtsai@mx.nthu.edu.tw. Phone: ; Fax: S1

2 1. ADDITIONAL TEM AND SEM IMAGES S2

3 S3

4 Figure S1. Additional TEM and SEM images and analyses of CuxO-NPs with different temperature (Tdec). CCu = 5 wt%. (a) Tdec = 400 C. (b) Tdec = 500 C. (c) Tdec = 700 C. S4

5 Figure S2. Additional SEM images and analyses of CuxO-NPs with different concentrations of Cu precursor. Tdec = 500 C. (a) CCu = 0.1 wt%. (b) CCu = 1 wt%. (c) CCu = 5 wt%. S5

6 Figure S3. Additional SEM images and analyses. (a) CuAlOx-NP. (b) CuCeOx-NP S6

7 Figure S4. Representative TEM images of the bare CuxO-NP with different CCu. 1: CCu = 1 wt%. 2: CCu = 5 wt%. The TEM micrographs show dc,cuo 16 nm (Figure S4), indicating that we were unable to identify the subtle difference through the image analysis. 2. TGA ANALYSIS According to the mass loss measured by TGA, we analyze molecular formula as follows: (a) For CuCeOx-NP Step 1 (from 50 C to 218 C): desorption of water from the precursors, 2*Ce2(OH)(NO3)5 (molecular mass: 607 g/mol) and Cu2(OH)3NO3 (molecular mass: S7

8 239 g/mol). The mass loss was 4.6 %. Step 2 (from 218 C to 226 C): conversion of Ce2(OH)(NO3)5 to Ce2(OH)3(NO3)3, The mass loss was 16.1 % (Theoretic value was 11.8 %). Step 3 (from 226 C to 350 C): thermal decomposition from Ce2(OH)3(NO3)3 + Cu2(OH)3NO3 to CuO + CeO2, The mass loss was 31.6% (Theoretic value 28 %). (b) For CuAlOx-NP Step 1: At 50 C to 106 C, precursor 2*Al2(OH)(NO3)5 (molecular mass: 381 g/mol) and Cu2(OH)3NO3 (molecular mass: 239 g/mol ) desorption of water, weight loss 3.0 %. Step 2: At 106 C to 174 C, hydroxide precipitate from 2*Al2(OH)(NO3)5 to Al2(OH)3(NO3)3, weight loss 17.8 % (Theoretic value 17.4 %). Step 3: At 174 C to 400 C, thermal decomposition of the dried precursor, Cu2(OH)3NO3 + Al2(OH)3(NO3)3, to CuO + Al2O3 and CuAl2O4, weight loss 47.5 % (Theoretic value 44.5 %) In general, the temperature range was identical with the sample using Ce-only and Al-only precursor, and the decline in the mass is also close to with the estimate based on the theoretical values of dried precursors. S8

9 3. CONVERSION RATIO OF O 2 VERSUS SURROUNDING TEMPERATURE (T SUR ) AND ADDITIONAL ACTIVITY TEST OF CO OXIDATION Figure S5 shows the conversion ratio of O2 versus the surrounding temperature (Tsur). We observed the light-off effect started at the same Tsur by measuring the CO conversion reported in the main text (i.e., 100 % of CO conversion). Because the molar ratio of CO to O2 was equal to 1, we observe that O2 conversion ratio plateaued at 50 %. Figure S5. Conversion ratios of O2 versus the surrounding temperatures (Tsur). CCO = 50 vol%, CO2 = 50 vol%. We also performed an activity test using CuxO-NP physically mixed with CeO2-only nanoparticles (CeO2-NPs), by which we introduce the surface oxygen (or the induced S9

10 oxygen vacancies) of CeO2 to the catalyst and minimize the formation of the Cu-Ce-O interface. As shown in Figure S6, the catalytic activity was much lower than CuCeOx- NP (i.e., with much higher extent of Cu-Ce-O interface). The results indicate that the formation of Cu-Ce-O interface is critical to the improvement of catalytic activity. Figure S6. Activity test of CO oxidation using CuxO-NP physically mixed with CeO2- only NP 4. DROPLET SIZE DISTRIBUTION AND THE CALCULATED PARTICLE SIZE DISTRIBUTION OF CUO The size distribution of the nebulized droplets was calculated by measuring particle size distribution of the diluted sucrose solution. 1 Assuming that every droplet contains the same concentration of sucrose, the droplet size can be calculated using Eq. S1: 1 C (S1) S10

11 Here ds is sucrose diameter, dd is droplet diameter, ρ is sucrose density, and Cv is the mass concentration of sucrose in the solution. Figure S7a shows the particle size distribution of dried sucrose particle with a concentration of 1 wt%. The corresponding droplet size distribution, as shown in Fig. S7b, is calculated using Eq. S1. As shown in Figure S7b, The peak droplet diameter was 375 nm, and the full width at half maximum was 600 nm. We then calculated the expected particle size distribution of CuxO-NP based on the droplet size distribution and compared the results with the experimental data measured by DMA. Here we assume the density of CuO is 6.31 g/cm 3. Figure S8 shows the calculated particle size distribution of CuxO-NP when CCu = 5 wt%. As seen, the calculated peak diameter of CuxO-NP was 44.7 nm, close to the experimental data, 50 nm. The result can also be used to confirm the peak size of nebulized droplets, 375 nm. S11

12 Figure S7. (a) Particle size distribution of dried sucrose. Concentration of sucrose: 1 wt%. (b) Size distribution of nebulized droplets using Eq. S1, based on the result of Fig. S7a. S12

13 Figure S8. The calculated particle size distribution of CuxO-NP using the droplet size distribution shown in Fig. S7b, versus the experimental data measured by DMA. CCu = 5 wt%. 5. CO-TPR OF CEO 2 -ONLY NPS Figure S9 shows the CO-TPR analysis of the CeO2-NPs. We observed that one peak at a surrounding temperature (Tsur) of 206 C is related to the transformation of Ce(IV) to Ce(III) at the surface of CeO2-NPs. Since the peak temperature of CeO2-NPs reduction is higher than the reduction peak temperatures of CuCeOx-NP and CuxO-NP, the low reduction peak temperature in the CuCeOx-NP is attributed to the reduction of CuO promoted by the synergistic effect at the Cu-Ce-O interface. S13

14 Figure S9. CO-TPR of CeO2-NPs vs CuCeOx-NP 6. CALCULATION OF THE CRYSTALLITE SIZE OF NP The crystallite size of NP, dc, was calculated using Debye-Scherrer equation: 2 Where K is the Scherrer constant ( 1), β is the full-width at half maximum of the XRD (1). peak with the highest diffraction intensity in the diffractogram (i.e., as the representative additional broadening in radians), and θ is the diffraction angle. REFERENCE (1) Kaufman, S. L. Electrospray Diagnostics Performed by Using Sucrose and Proteins in the Gas-Phase Electrophoretic Mobility Molecular Analyzer (GEMMA). Anal Chim Acta 2000, 406, S14

15 (2) Langford, J. I.; Wilson, A. J. C. Scherrer after 60 Years - Survey and Some New Results in Determination of Crystallite Size. J Appl Crystallogr 1978, 11, S15