CuBi 2 O 4 Prepared by the Polymerized Complex Method for Gas-Sensing Applications

Transcription

1 Supporting Information CuBi 2 O 4 Prepared by the Polymerized Complex Method for Gas-Sensing Applications Yun-Hyuk Choi,, * Dai-Hong Kim, and Seong-Hyeon Hong Department of Chemistry, Texas A&M University, College Station, Texas , United States Department of Materials Science and Engineering and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul , Republic of Korea * Corresponding author yunhyuk.choi@chem.tamu.edu (Y.-H. Choi) S-1

2 Figure S1. Flow diagram for powder synthesis of CuBi 2 O 4 by the polymerized complex method (or Pechini method). S-2

3 Figure S2. XRD pattern of the black precursor powder obtained via burning of the polyesterified polymer resin at 400 C for 5 h in air. The XRD pattern is identified in accordance with the JCPDS data of CuBi 2 O 4, CuO, and Bi 2 O 3. S-3

4 Figure S3. Nitrogen adsorption/desorption isotherms of the CuBi 2 O 4 powders prepared through calcination at 500, 600, and 700 C for 6 h in air. S-4

5 Figure S4. XRD patterns of (a) the black precursor powder obtained at 400 C for 5 h in air and (b) the CuBi 2 O 4 powder formed through further calcination of the black precursor powder at 700 C for 6 h in air, in the polymerized complex synthesis performed with a 1:1 mole ratio of Cu(II) and Bi(III) precursors. Each XRD pattern is identified in accordance with the JCPDS data of CuBi 2 O 4, CuO, and Bi 2 O 3. S-5

6 Figure S5. (a) FE-SEM image and (b) XRD pattern of the CuBi 2 O 4 powder obtained through calcination at 700 C for 6 h in air, in the polymerized complex synthesis performed with copper(ii) formate tetrahydrate instead of copper(ii) chloride dihydrate. The XRD pattern is identified in accordance with the JCPDS data of CuBi 2 O 4. S-6

7 Figure S6. XPS Cu 2p spectra acquired for the CuBi 2 O 4 powders prepared through calcination of the precursor powder at (a) 500, (b) 600, and (c) 700 C for 6 h in air. Each Cu 2p 3/2 peak is deconvoluted into two subpeaks arising from the Cu(II) and Cu(I) components with their atomic fraction. S-7

8 Figure S7. XPS Bi 4f spectra acquired for a commercial Bi 2 O 3 powder (99.999% purity, Strem Chemicals) and the CuBi 2 O 4 powders prepared through calcination of the precursor powder at 500, 600, and 700 C for 6 h in air. S-8

9 Figure S8. FE-SEM images of the fractured planes of the bulk CuBi 2 O 4 pellet sintered at 700 C for 12 h, acquired at various magnification levels. S-9

10 Figure S9. (a) FE-SEM images and (b) XRD pattern of the CuO powder obtained by the polymerized complex method. The XRD pattern is identified in accordance with the JCPDS data of CuO. (c) Cross-sectional FE-SEM image of the CuO film prepared on a SiO 2 /Si substrate with the synthesized CuO powder. S-10

11 Figure S10. Photograph of the fabricated gas sensor. S-11

12 Figure S11. Gas-response values of CuO sensor. (a) Gas-response values measured at the operating temperatures of C toward C 2 H 5 OH gas, shown as a function of the gas concentration. (b) Gas-response values measured at the operating temperature of 400 C toward NH 3, CO, and H 2 gases, shown as a function of the gas concentration. S-12

13 Figure S12. (a) Gas-response transient of the CuBi 2 O 4 sensor prepared using the 500 C-calcined powder and (b) its gas-response values shown as a function of the gas concentration toward ppm C 2 H 5 OH gas. Inset shows the plot on a logarithmic scale. The gas-response transient and response values were obtained with the operating temperature of 400 C. S-13

14 Figure S13. Reversible response transient of the CuBi 2 O 4 sensor with the 500 C-calcined powder, acquired by repeated measurement for more than 5 h toward 10 ppm C 2 H 5 OH at an operating temperature of 400 C. S-14

15 Materials Target reducing gas Response (R g /R a ) Optimum operating temperature Reference ZnFe 2 O 4 5 ppm C 2 H 5 OH C (S1) MgFe 2 O 4 50 ppm C 2 H 5 OH C (S2) ZnFe 2 O 4 50 ppm C 2 H 5 OH C (S3) ZnCo 2 O 4 50 ppm C 2 H 5 OH C (S3) ZnCr 2 O 4 50 ppm C 2 H 5 OH C (S3) Ni 0.6 Zn 0.4 Fe 2 O ppm C 2 H 5 OH C (S4) Ni 0.6 Zn 0.4 Fe 2 O 4 : Pd (1.0 wt.%) 100 ppm C 2 H 5 OH C (S4) CaFe 2 O ppm C 2 H 5 OH C (S5) ZnFe 2 O ppm C 2 H 5 OH C (S6) Zn 0.6 Mn 0.4 Fe 2 O ppm C 2 H 5 OH C (S6) Zn 0.8 Mn 0.2 Fe 2 O ppm C 2 H 5 OH C (S6) NiFe 2 O ppm C 2 H 5 OH C (S7) CrNbO ppm C 2 H 5 OH C (S8) CuFe 2 O ppm C 2 H 5 OH C (S9) ZnFe 2 O ppm C 2 H 5 OH C (S10) ZnFe 2 O 4 10 ppm C 2 H 5 OH C (S11) 20 ppm C 2 H 5 OH C 50 ppm C 2 H 5 OH C 100 ppm C 2 H 5 OH C 200 ppm C 2 H 5 OH C 500 ppm C 2 H 5 OH C CuBi 2 O 4 5 ppm C 2 H 5 OH C This work 10 ppm C 2 H 5 OH C 25 ppm C 2 H 5 OH C 50 ppm C 2 H 5 OH C 100 ppm C 2 H 5 OH C 250 ppm C 2 H 5 OH C 500 ppm C 2 H 5 OH C 1000 ppm C 2 H 5 OH C CuAlO 2 10 ppm NH C (S12) CaFe 2 O ppm NH C (S5) Ni 0.6 Zn 0.4 Fe 2 O ppm NH C (S4) CuNb 2 O ppm NH C (S13) CrNbO ppm NH C (S8) CuFe 2 O ppm NH C (S9) CuBi 2 O 4 50 ppm NH C This work 100 ppm NH C 250 ppm NH C 500 ppm NH C 1000 ppm NH C Continued below S-15

16 Materials Target reducing gas Response (R g /R a ) Optimum operating temperature Reference CuNb 2 O ppm H C (S13) CuFe 2 O ppm H C (S9) Mg 0.5 Zn 0.5 Fe 2 O ppm H C (S14) CuBi 2 O 4 50 ppm H C This work 100 ppm H C 250 ppm H C 500 ppm H C 1000 ppm H C CuAlO 2 20 ppm CO C (S12) LaFeO ppm CO C (S15) LaFe 0.9 Co 0.1 O ppm CO C (S15) ZnFe 2 O ppm CO C (S10) Mg 0.5 Zn 0.5 Fe 2 O ppm CO C (S14) CuBi 2 O 4 50 ppm CO C This work 100 ppm CO C 250 ppm CO C 500 ppm CO C 1000 ppm CO C Table S1. Reported gas-response values for other multicomponent oxides. S-16

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