Water Gas Shift Reaction on Cu and Au Nanoparticles Supported on CeO₂(111) and ZnO(000$\bar 1$): Intrinsic Activity and Importance of Support Interactions

Abstract

Currently, the primary source of hydrogen is steam reforming from hydrocarbons. The reformed fuel contains 1-10 % CO.[1, 2] The water gas shift reaction (WGS, CO + H 2 O! H 2 + CO 2 ) and preferential CO oxidation (2 CO + O 2 ! 2 CO 2 ) processes are critical in providing clean hydrogen for polymer electrolyte membrane fuel cells and other industrial applications.[1-3] Conventional WGS catalysts (e.g., Cu on zinc oxide) meet the needs of large stationary applications. [4] Improved air-tolerant, cost-effective WGS catalysts for lower-temperature processing are needed to enable mobile fuel-cell applications. [1][2][3]5] Recently, Au/CeO 2 and Cu/CeO 2 materials were reported to be very promising catalysts for the lower-temperature WGS reaction. [6,7] There is no generally accepted picture for the role of ceria and the metal in the WGS reaction. The existence and role of reduced metal nanoparticles versus cationic metal centers (e.g., Au d+ ) are debated. [5][6][7] Very recent in situ measurements by near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy show that Cu d+ and Au d+ species are not stable under the typical conditions of the WGS reaction.

FeOx supported single‐atom Pd bifunctional catalyst for water gas shift reaction

“…[41][42][43] As the dissociation of H 2 O molecules is a high-barrier step, the presence of reducible oxide is more favorable than inert oxide, especially more oxygen vacancies further promoting the activation of H 2 O. 44,45 The formation of oxygen vacancies on FeO x can be evaluated from H 2 -TPR experiments. The profiles are shown in Figure 9 and the H 2 consumption amounts are summarized in Table 2.…”

High Activity of Ce1−xNixO2−y for H2 Production through Ethanol Steam Reforming: Tuning Catalytic Performance through Metal–Oxide Interactions

“…The amount of hydrogen produced was normalized according to the exposed active area of the sample face that contained nickel. [35] …”

Insights into the Nature of Formate Species in the Decomposition and Reaction of Methanol over Cerium Oxide Surfaces: A Combined Infrared Spectroscopy and Density Functional Theory Study

“…Moreover, the active role of ceria in the important watergas-shift (WGS, CO + H 2 O −→ CO 2 + H 2 ) and steam reforming of alcohols reactions for hydrogen production, in particular methanol (MSR, CH 3 OH + H 2 O −→ CO 2 + 3 H 2 ), has been widely reported. [9][10][11][12][13][14][15][16][17] The possibility of understanding the mechanism of catalytic reactions, which is essential for rational catalyst design, depends very much on the chances of isolating intermediates in the study of each step in the catalytic cycle. It has been argued that formate (HCOO) transient species might be playing intermediate or spectactor roles during WGS [18][19][20][21][22][23] and MSR 24 or its reverse reaction, [25][26][27][28] that is, the methanol synthesis from carbon oxides.…”