Mechanistic insight into effect of doping of Ni on CO2reduction on the (111) facet of Cu: thermodynamic and kinetic analyses of the elementary steps.
A systematic mechanistic investigation of CO2reduction on a Ni-modified Cu(111) surface is performed based on an extensive set of density functional theory (DFT) calculations by focusing on the hydrocarbon CH4formation pathways. By carefully analyzing reduction pathways on the Ni-modified Cu(111) surface, some important mechanistic information is deduced. The presence of Ni stabilizes all reaction intermediates, and thus reduces the activation barrier for almost all CO2reduction steps. Most importantly, it can considerably lower than the activation barrier of CO2hydrogenative dissociation into CO, which is the rate-determining step of CO2reduction on a pure Cu(111) surface. Thus, the doping of Ni atom is able to activate CO2, leading to enhanced surface activity of CO2reduction into hydrocarbons. Notably, the activation barriers that are required for CH4and CH3OH formation are almost all easily overcome through the thermoactive process at ambient temperatures after doping of Ni atom. Thus, a higher CH4and CH3OH yield may be expected in the presence of the doped Ni atom. Thermodynamic analyses indicate that doping of Ni may reduce the overpotential of CO formation through CO2hydrogenative dissociation. On this basis, two decriptors may be proposed in order to describe the catalytic activity of Cu-based catalysts for CO2reduction, and a perfect Cu-based alloy in CO2reduction should moderately bind CO and form and reduce CO more easily. Simutaneously, CO hydrogenation occurs more easily on the (111) facet of Ni-modified Cu than dimerization, thereby the selectivity of (111) facet of Cu on production CH4is further confirmed to some degree. The present study reveals a rich reaction chemistry and provides new insights to guide the rational design of Cu-based alloy catalysts for hydrocarbons formation from CO2reduction. Graphical Abstract Reduction pathways of CO2into hydrocarbonsᅟ.
College of Chemistry and Chemical Engineering, Hunan University of Arts and Science, Changde, 415000, China. oulihui666@126.com.
Li-Hui
LH
Ou
CH4; Carbon dioxide reduction; Minimum energy paths; Ni-modified Cu(111)
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