CO₂ Activation on Ni(111) and Ni(110) Surfaces in the Presence of Hydrogen

Abstract

The structure sensitivity of CO2 activation in the presence of H2 has been identified by ambient-pressure X-ray photoelectron spectroscopy (APXPS) on Ni(111) and Ni(110) surfaces under identical reaction conditions. Based on the APXPS results and computer simulations, we propose that, around room temperature, the hydrogen-assisted activation of CO2 is the major reaction path on Ni(111), while the redox pathway of CO2 prevails on Ni(110). With increasing temperature, the two activation pathways are activated in parallel. While the Ni(111) surface is fully reduced to the metallic state at elevated temperatures, two stable Ni oxide species can be observed on Ni(110). Turnover frequency measurements indicate that the low-coordinated sites on Ni(110) promote the activity and selectivity of CO2 hydrogenation to methane. Our findings provide insights into the role of low-coordinated Ni sites in nanoparticle catalysts for CO2 methanation.

Tuning the CO2 Hydrogenation Activity via Regulating the Strong Metal–Support Interactions of the Ni/Sm2O3 Catalyst

“…As shown in Figure a,b, the main surface species of Ni/Sm 2 O 3 adsorbed is carbon monoxide (bridged CO: 1930 cm –1 and multibonded CO: 1860 cm –1 ) and formates (*HCOO: 1390 and 1595 cm –1 ). − The *CO species can originate from the decomposition of carboxyl (*COOH). The presence of carboxyl and formate intermediates indicates that the CO 2 activation pathway follows a hydrogen-assisted mechanism . In addition, both *CO and *HCOO species are active intermediates capable of reacting with *H species to generate CH 4 .…”