Synergistic effect in catalysis has been explored extensively to improve catalyst activity and selectivity. This effect is often observed from a binary or multicomponent system where different chemical identities on the surface of the catalyst can help to control reactant adsorption, activation and product desorption to facilitate a specific catalytic reaction. Here we present two examples to demonstrate the effect of controlling metal nanoparticle (NP) interactions with nanoscale-supports on improving NP catalytic selectivity for electrochemical reduction of CO2. Monodisperse Cu NPs, once prepared and assembled on N-doped graphene (NG), can show both N-doping and Cu NP-dependent reduction activity/selectivity for the electrochemical reduction of CO2 in 0.5 M KHCO3. For example, 7 nm Cu NPs assembled on the pyridinic-N rich G (p-NG) show the promising reduction activity and selectivity to ethylene (C2H4): among formate, ethylene, ethane and methane detected, C2H4 is present as a major product (19% Faradaic efficiency and 79% ethylene selectivity) at -0.9 V vs. RHE (reversible hydrogen electrode). Once these Cu NPs are coated with a layer of SnO2, the core/shell NPs show SnO2 thickness dependent catalytic selectivity - the NPs with a 1.8 nm thick SnO2 coating show SnO2-like activity and selectivity to formate, while those with a 0.8 nm thick coating become highly selective to CO (~93% FE at -0.7 V vs. RHE). Modeling study suggests that around the 0.8 nm SnO2 shell, it is the concurrent lattice compression of SnO2 and Cu diffusing from core that leads to the preferential CO production. Our studies suggest that controlled assembly of a nano-catalyst on a doped graphene or a metal NP surface is an important strategy to develop efficient NP catalyst for selective CO2 reduction.

Controlling metal nanoparticle interactions with nanoscale-supports to enhance nanoparticle catalysis for selective CO2 reduction

254th National Meeting (2017)

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