Junctions between CuO_x and ZnO_y in sensors for CO and catalystsfor CO hydrogenation

Abstract

Addition of CuO_xto defective ZnO_y(0.92<y<1.00) yielded a dispersed catalyst that produced methanol at 523 K and 2 MPa with a selectivity (relative to CH₄) which was higher than that for a unit area of ZnO_yor CuO_xalone. Copper oxide–zinc oxide polycrystalline films (prepared by ion beam sputter deposition) were as stoichiometric as the dispersed samples with junctions best represented as CuO_x/ZnO_y(withx close to 0.5 and y close to 1.0). Photo-STM reveals for the first time the width and nature of the n/p junction, although the gradient of the depletion zone is shallower on the ZnO side of the junction (which is not expected from recent postulates). Responses to CO and H₂ were more representative of CuO_xthan ZnO_y. The properties of such junctions and their role in CO adsorption, catalysis and sensing is discussed, together with the relationship between catalytic and sensor science. Active sites at such junctions may have been detected as those binding CO₂^– with an IR band at 1557 cm^–1 which decompose to release CO₂ or convert to formyl species (and then methanol) depending upon the prevailing conditions.

References

1. A. R. Frederickson and A. S. Karakashian, J. Appl. Phys., 1995, 77, 1627.
2. C. H. Townes, A. N. Holden, J. Bardeen and F. R. Merritt, Phys. Rev., 1947, 71, 644.
3. P. R. Fischer and G. L. Richmond, ACS Chicago, 1995, 210, 063-COLL.
4. G. L. Richmond, J. M. Robinson and U. L. Shannon, Prog. Surf. Sci., 1988, 28, 1.
5. T. Seiyama and S. Kagawa, Anal. Chem., 1966, 38, 1069; T. Nenov and S. Yordanov, Sens. Actuators B, 1992, 8, 117; S. T. Jun and G. M. Choi, Sens. Actuators B, 1994, 17, 175.
6. A. R. Raju and C. N. R. Rao, Sens. Actuators B, 1991, 3, 305; E. Traversa and A. Bearzotti, J. Ceram. Soc. Jpn., 1995, 103, 11; J. Muller and S. Weissenrieder, Fresenius J. Anal. Chem., 1994, 349, 380; V. V. Malyshev, A. A. Vasiliev, A. V. Eryshkin, E. A. Koltypin, Y. I. Shubin, A. I. Buturlin, V. A. Zaikin and G. B. Chakhunashvili, Sens. Actuators B, 1992, 10, 11.
7. Q. J. Gu, Z. L. Ma, N. Liu, X. Ge, W. B. Zhao, Z. Q. Xue, S. J. Pang and Z. Y. Hua, Surf. Sci., 1995, 327, 241.
8. A. V. Chadwick, N. V. Russell, A. R. Whitham and A. Wilson, Sens. Actuators B, 1994, 18, 99.
9. Y. Ushio, M. Miyayama and H. Yanagida, Sens. Actuators B, 1994, 17, 221; Jpn. J. Appl. Phys. I, 1994, 33, 1136.
10. Y. Nakamura, H. Yoshioka, M. Miyayama, H. Yanagida, T. Tsurutani and Y. Nakamura, J. Electrochem. Soc., 1990, 137, 940.
11. P. Porta, M. C. Campa, G. Fierro, M. Lojacono, G. Minelli, G. Moretti and L. Stoppa, J. Mater. Chem., 1993, 3, 505; J. Skrzypek, J. Sloczynski and S. Ledakowicz, Methanol Synthesis, Polish Scientific Publishers, 1994; J. C. Slaa, G. J. M. Weierink, J. G. Vanommen and J. R. H. Ross, Catal. Today, 1992, 12, 481; J. C. Slaa, J. G. Vanommen and J. R. H. Ross, Catal. Today, 1992, 15, 129; G. C. Chinchen, K. C. Waugh and D. A. Whan, Appl. Catal., 1986, 25, 101; I. Boz, D. Chadwick, I. S. Metcalfe and K. Zheng, Stud. Surf. Sci. Catal., 1993, 75, 2785; M. Bowker, H. Houghton, K. C. Waugh, T. Giddings and M. Green, J. Catal., 1983, 84, 252; M. Bowker, Vacuum, 1983, 33, 669; J. C. Amphlett, R. F. Mann, C. McKnight and R. D. Weir, Proc. Intersoc. Energy Convers. Energy Conf., 1985, 20, 2772.
12. K. L. Siefering and G. L. Griffin, Surf. Sci., 1989, 207, 525.
13. V. Bolis, B. Fubini, E. Giamello and A. Reller, J. Chem. Soc., Faraday Trans. 1, 1989, 85, 855.
14. M. A. Vest, K. Lui and H. H. Kung, J. Catal., 1989, 120, 231; G. M. Schwab and H. Seemueller, Mem. Soc. Roy. Sci., Liege Collect., 1971, 8, 55; C. T. Au, W. Hirsch and W. Hirschwald, Surf. Sci., 1988, 199, 507.
15. J. C. J. Bart and R. P. A. Sneeden, Catal. Today, 1987, 2, 1.
16. H. S. Taylor and C. O. Strother, J. Am. Chem. Soc., 1934, 56, 586; R. R. Gay, M. H. Nodine, V. E. Heinrich, H. J. Zeiger and E. I. Solomon, J. Am. Chem. Soc., 1980, 102, 6752; G. L. Griffin and J. T. Yates, J. Chem. Phys., 1982, 77, 3751.
17. E. Mollwo, G. Muller and P. Wagner, Solid State Commun., 1973, 13, 1283; R. G. Herman, K. Klier, G. W. Simmons, B. P. Finn, J. B. Bulko and T. Kobylinski, J. Catal., 1979, 56, 407; T. Arunarkavalli, G. U. Kulkarni and C. N. R. Rao, Catal. Lett., 1993, 20, 259.
18. M. A. M. Luengo, P. A. Sermon, Y. Sun, M. S. W. Vong and V. A. Self, Solid State Ionics, 1997, in press.
19. R. A. Hadden, P. J. Lambert and C. Ranson, Appl. Catal. A, 1995, 122, L1.
20. J. C. Frost, Nature (London), 1988, 334, 577; R. Zhang, A. Ludviksson and C. T. Campbell, Catal. Lett., 1994, 25, 277; G. J. Millar, C. H. Rochester and K. C. Waugh, J. Chem. Soc., Faraday Trans. 1, 1992, 88, 2257, 3497.
21. J. E. Bailie, C. H. Rochester and G. J. Millar, Catal. Lett., 1995, 31, 333.
22. M. S. W. Vong, M. A. Yates, P. Reyes, A. Perryman and P. A. Sermon, Proc. 9th. Intern. Cong. Catal. The Chemical Institute of Canada, Ottawa, ed. M. J. Philips and M. Ternan, pp. 545–552.
23. S. S. Fu and G. A. Somorjai, Surf. Sci., 1990, 237, 87; S. V. Didziulis, K. D. Butcher, S. L. Cohen and E. I. Solomon, J. Am. Chem. Soc., 1989, 111, 7110.
24. E. P. S. Barrett, G. C. Georgiades and P. A. Sermon, Sens. Actuators B, 1990, 1, 116.
25. P. J. Moller, S. A. Komolov, E. F. Lazneva and E. H. Pedersen, Surf. Sci., 1995, 323, 102.
26. G. S. Rohrer and D. A. Bonnell, Surf. Sci., 1991, 247, L195; K. Itaya and E. Tomita, Surf. Sci., 1989, 219, L515; A. B. Boffa, H. C. Galloway, P. W. Jacobs, J. J. Benitez, J. D. Batteas, M. Salmeron, A. T. Bell and G. A. Somorjai, Surf. Sci., 1995, 326, 80.
27. V. A. Self and P. A. Sermon, Rev. Sci. Instrum., 1996, 67, 2096.
28. S. R. Morrison, Surf. Sci., 1971, 27, 586; 1975, 50, 329.
29. A. L. Boyce, P. A. Sermon, M. S. W. Vong and M. A. Yates, React. Kinet. Catal. Lett., 1991, 44, 309.
30. Y. Mizokawa and S. Nakamura, Jpn. J. Appl. Phys., 1977, 16, 1073.
31. K. M. Sancier, J. Phys. Chem., 1972, 76, 2527.
32. P. A. Sermon, M. A. Martin-Luengo and Y. Wang, Proc. 10th Int. Congr. Catal. Hungary, Elsevier Sci., ed. Guczi, F. Solymosi and P. Tetenyi, 1992, pp. 2773–2776.
33. J. J. Carberry, J. Catal., 1987, 107, 248.
34. D. Stirling, F. S. Stone and M. S. Spencer, Proc. 10th Int. Congr. Catal. Hungary, Elsevier Sci., ed. Guczi, F. Solymosi and P. Tetenyi, 1992, p. 1507.
35. R. P. Eischens, W. A. Pliskin and S. A. Francis, J. Chem. Phys., 1954, 22, 1786; R. P. Eischens and N. A. Pliskin, Adv. Catal., 1958, 10, 2.
36. M. A. Martin-Luengo, P. A. Sermon and Y. Wang, Stud. Surf. Sci. Catal., 1993, 75C, 2773.
37. H. H. Kung, Catal. Rev., 1980, 22, 235; E. L. Muetterties and J. Stein, Chem. Rev., 1979, 79, 479.
38. A. A. Tsyganenko, J. Lamotte, J. Saussey and J. C. Lavalley, J. Chem. Soc., Faraday Trans. 1, 1989, 85, 2397.
39. C. T. Campbell, K. A. Daube and J. M. White, Surf. Sci., 1987, 182, 458.
40. S. W. Gaarenstroom and N. Winograd, J. Chem. Phys., 1977, 67, 3500.
41. J. F. Walsh, R. Davis, C. A. Muryn, G. Thornton, V. R. Dhanak and K. C. Prince, Phys. Rev. B, 1993, 48, 14749.
42. J. A. Rodriguez and C. T. Campbell, Surf. Sci., 1988, 194, 475.
43. J. C. Lavalley and R. T. J. Saussey, 6th. Sov. Fr. Seminar. Po. Katal. Sb. Dokl. M97, 1983; R. C. Baetzold, J. Phys. Chem., 1985, 89, 4150.
44. R. Burch, R. J. Chappell and S. E. Golunski, J. Chem. Soc., Faraday Trans. 1, 1989, 85, 3569; R. Burch and R. J. Chappell, Appl. Catal., 1988, 45, 131; R. Burch, R. J. Chappell and S. E. Golunski, Catal. Lett., 1988, 1, 439; M. J. Chung, D. J. Moon, H. S. Kim, K. Y. Park and S. K. Ihm, J. Mol. Catal. A, 1996, 113, 507.
45. W. Schottky, Naturwissenschaften, 1938, 26, 843.
46. E. Weiss and M. Folman, J. Chem. Soc., Faraday Trans. 1, 1986, 82, 2025.
47. J. Pritchard, Nature (London), 1990, 343, 592.
48. G. M. Schwab and R. Siegert, Z. Phys. Chem., 1966, 50, 191.
49. M. Bartkowiak, G. D. Mahan, F. A. Modine and M. A. Alim, Jpn. J. Appl. Phys. 2, 1996, 35-4A, 414; J. Appl. Phys., 1996, 79, 273.
50. Y. Nakamura, K. Watanabe, S. J. Jung, H. Osawa, H. Yoshioka and H. Yanagida, J. Catal., 1995, 153, 350; C. G. Vayenas, S. Bebelis and S. Ladas, Nature (London), 1990, 343, 625.