The chemisorption and reactions of formic acid on Cu films on ZnO (000)-O

Ludviksson, A.; Zhang, R.; Campbell, Charles T.; Griffiths, K.

doi:10.1016/0039-6028(94)91157-6

Cited by 50 publications

(36 citation statements)

References 52 publications

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“…Differences in reactivity of the ZnO surfaces for the adsorption and decomposition of methanol [86][87][88][89][90] as well as formic acid [86,[91][92][93][94] on the polar and the non-polar surfaces have already been known for a long time. It was proposed that the interaction of methanol with any of the common ZnO surfaces readily led to the formation of methoxy (methoxide) species (CH 3 O) due to a heterolytic splitting of the O-H bond [87,90].…”

Section: The Interaction With Methanolmentioning

confidence: 99%

The surface chemistry of ZnO nanoparticles applied as heterogeneous catalysts in methanol synthesis

et al. 2009

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Section: The Interaction With Methanolmentioning

confidence: 99%

The surface chemistry of ZnO nanoparticles applied as heterogeneous catalysts in methanol synthesis

et al. 2009

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“…A quantitative comparison of these reactivities will be presented in the results section below. Among the major qualitative findings is that formate decomposes cleanly to CO 2 and H 2 in vacuum [24] or inert gas atmospheres [20]. Some previous studies indicate that H 2 -containing atmospheres increase the rate of decomposition, implying that reductive chemistry, including methanol formation, is involved.…”

Section: Introductionmentioning

confidence: 96%

Simultaneous MS-IR Studies of Surface Formate Reactivity Under Methanol Synthesis Conditions on Cu/SiO2

et al. 2009

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The coverages and surface lifetimes of copperbound formates on Cu/SiO 2 catalysts, and the steady-state rates of reverse water-gas shift and methanol synthesis have been measured simultaneously by mass (MS) and infrared (IR) spectroscopies under a variety of elevated pressure conditions at temperatures between 140 and 160°C. DCOO lifetimes under steady state catalytic conditions in CO 2 :D 2 atmospheres were measured by 12 C-13 C isotope transients (SSITKA). The values range from 220 s at 160°C to 660 s at 140°C. The catalytic rates of both reverse water gas shift (RWGS) and methanol synthesis are *100-fold slower than this formate removal rate back to CO 2 ? 1/2 H 2 , and thus they do not significantly influence the formate lifetime or coverage at steady state. The formate coverage is instead determined by formate's rapid production/decomposition equilibrium with gas phase CO 2 ? H 2 . The results are consistent with formate being an intermediate in methanol synthesis, but with the ratecontrolling step being after formate production (for example, its further hydrogenation to methoxy). A 2-3 fold shorter life time (faster decomposition rate) was observed for formate under reactions conditions, with both D 2 and CO 2 present, than in pure Ar or D 2 ? Ar alone. This effect, due in part to the effects of the coadsorbates produced under reaction conditions, illustrates the importance of using in situ techniques in the study of catalytic mechanisms. The carbon which appears in the methanol product spends a longer time on the surface than the formate species, 1.8 times as long at 140°C. The additional delay on the surface is attributed in part to readsorption of methanol on the catalyst, thus obscuring the mechanistic link between formate and methanol.

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“…Campbell and co-workers studied the adsorption of CO and HCO 2 H on O-terminated ZnOð000 " 1Þ and Znterminated ZnO (0001) on both of which surfaces Cu had been deposited [15][16][17]. The materials were considered to be models for the Cu/ZnO methanol synthesis catalyst.…”

Section: Introductionmentioning

confidence: 99%

On the mechanism of methanol synthesis and the water-gas shift reaction on ZnO

2006

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Zinc oxide catalyses both methanol synthesis and the forward and 'everse water-gas shift reaction (f-and r-WGSR). Copper also catalyses both reactions, but at lower temperatures than ZnO. Presently the combination of Cu and ZnO stabilized by Al 2 O 3 is the preferred catalyst for methanol synthesis and for the f-and r-WGSR. On Cu, the mechanism of methanol synthesis is by hydrogenation of an adsorbed bidentate formate [1] (the most stable adsorbed species in methanol synthesis), while the f-and r-WGSR proceeds by a redox mechanism. The f-WGSR proceeds by H 2 O oxidizing the Cu and CO, reducing the adsorbed oxide and the r-WGSR proceeds by CO 2 oxidising the Cu and H 2 , reducing it [2][3][4][5]. Here we show that the mechanisms of both reactions are subtly different on ZnO. While methanol is shown to be formed on ZnO through a formate intermediate, it is a monodentate formate species which is the intermediate; the f-and r-WGS reactions also proceed through a formate -a bidentate formate -in sharp contrast to the mechanism on Cu.

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The chemisorption and reactions of formic acid on Cu films on ZnO (000)-O

Cited by 50 publications

References 52 publications

The surface chemistry of ZnO nanoparticles applied as heterogeneous catalysts in methanol synthesis

The surface chemistry of ZnO nanoparticles applied as heterogeneous catalysts in methanol synthesis

Simultaneous MS-IR Studies of Surface Formate Reactivity Under Methanol Synthesis Conditions on Cu/SiO2

On the mechanism of methanol synthesis and the water-gas shift reaction on ZnO

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