Carbon‐Supported NiZnO Nanoparticles for Electrochemical Reduction of CO 2 to Hydrocarbons

A compelling approach to close the carbon cycle is electrochemical CO 2 reduction. Recently, it was demonstrated that polarized Ni catalysts can form value‐added hydrocarbon products like ethylene in this reaction. However, the competing hydrogen evolution reaction significantly lowers their selectivity. We investigate the effects of ZnO on the catalytic performance of well‐defined carbon‐supported NiO nanoparticles of 5–6 nm. Adding small amounts of ZnO to the highly dispersed NiO nanoparticles (in 20:1 Ni:Zn ratio) initially improves the Faradaic efficiency to C 1−3 hydrocarbons from 4.6% to 5.7% at −1.1 V vs RHE, but adding more ZnO (10:1 Ni:Zn) favors the competing hydrogen evolution reaction. CO was detected only for the ZnO catalyst, suggesting electronic interaction between the nickel and zinc (oxide). After 2 h, the NiO catalyst outperforms the NiZnO catalysts in hydrocarbon selectivity. We attribute this to ZnO x promoting the hydrocarbon selectivity, whereas full ZnO reduction over time results in the formation of a NiZn alloy that favors hydrogen formation. Structural characterization after catalytic testing shows leaching of zinc but a high structural stability for the nickel nanoparticles. These results demonstrate that electronic promotion offers an interesting approach to modulate the catalytic performance of nickel toward long‐chain hydrocarbons.