**4. C1+ hydrocarbon selective electrocatalyst**

The production of hydrocarbons through electrochemical reduction of CO2 (a carbon-neutral fuel alternative to fossil fuels) is of interest because the infrastructure to store, transport and use methane and other hydrocarbons as fuel is already well established [64]. The major challenge for these products is to find the selective electrocatalysts to manage to reduce the CO2 molecule with 8 and 12 electrons (methane and ethane). Considering the stability of the CO2 molecule and the multielectron-coupled-proton pathways, high energy barriers are needed to overcome for the formation of the intermediates and final product [48].

According to major reports, Cu-based materials are the main type of electrocatalysts that can produce hydrocarbon compounds including CH4 and thus become the object under the most intensive study [65].

#### **4.1 Cu alloys**

Hirunsit et al. examined Cu3X alloys by using computational methods to examine the electrochemical reduction to CH4 [66]. In an important report, Kenis and co-workers recently reported the differences between ordered, disordered, and phase-separated Cu@Pd nanoparticles with respect to product selectivity [67]. Gewirth and co-workers showed that Cu-Ag alloys from additive-controlled electrodeposition exhibited ~60% FE for C2H4 in an alkaline flow electrolyzer. In this case, by tuning the Ag-loading an optimized C2H4 selectivity can be achieved. The Ag sites were believed to play the role of a promoter for CO formation during electrochemical CO2 reduction [68].
