DFT Investigation on the Competition of the Water–Gas Shift Reaction Versus Methanation on Clean and Potassium‐Modified Nickel(1 1 1) Surfaces. Issue 23 (4th November 2015)

• Record Type: Journal Article
• Authors: Zhou, Mingxia; Liu, Bin
• Is Part Of: ChemCatChem. Volume 7:Issue 23(2015:Dec.)
• Page Start: 3928
• Page End: 3935
• Publication Date: 2015-11-04
• Subjects: alkali metals -- density functional calculations -- nickel -- reaction mechanisms -- reactive intermediates; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201500547
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: We used periodic DFT calculations to investigate the effect of alkali promoter on the selectivity of the water‐gas shift reaction (WGSR) explicitly on the Ni(1 1 1) surface. On clean Ni(1 1 1), the WGSR redox and carboxyl pathways are both kinetically competitive. The selectivity of the WGSR can be affected by methanation on Ni, in which the C−O bond cleavage pathway of CHO is the most competitive. A Ni(1 1 1) surface modified with K adatoms was used to further understand the promoter effects on the WGSR selectivity. A combined energetic and kinetic analysis from DFT calculations indicates that the K adatom stabilizes certain reactive intermediates (e.g., H2 O, CO) thermodynamically but is energetically neutral or even repulsive toward other intermediates. As a result, WGSR pathways benefit from the presence of K adatoms compared to the competing methanation pathway. This study thus confirmed the promoting effects of alkali metals on the WGSR with DFT‐based mechanistic insights. Abstract : Scratching the surface : Alkali metals, such as K, exhibit promoting effects on certain catalytic reactions. By examining the elementary steps, this DFT study presents atomic‐level details on the promoting role of K in the water‐gas shift reaction versus methanation to improve hydrogen production selectivity.