The CO₂ valorization, i.e. its use in various electrochemical processes resulting in the production of carbon-based fuels and value-added chemicals, is of critical importance. Hence, the CO₂ reduction reaction (CO₂RR) has been widely investigated on electrocatalysts ranging from Cu-based nanostructures to carbonaceous materials. The latter often consist of carbon with atomically dispersed nitrogen and metals atoms (M-N-C, see Figure 1c). Such materials have been discussed in the literature, mostly using Fe as the metallic element ¹ (but also Mn, Ni, Co and Cu ^2–4), thus providing insights onto this family of electrocatalysts reactivity. But most of those electrocatalysts, as a result of their synthesis process, presents unwanted metallic contaminants ². Here, we synthesized M-N-C electrocatalysts (with M = Cr, Mn, Fe, Co, Ni, Cu & Zn) using the sacrificial support method, that resulted into non-contaminated M-N-C materials. We then combined electrochemistry and density functional theory to separate the electrocatalysts in several categories, based on their CO_ads binding strength. The strong CO_ads binder electrocatalysts (e.g. Cr, Mn and Fe-N-C) achieved a Faradaic efficiency up to 50% at 0.35 V vs. RHE (at pH = 7.5, in 0.1 M phosphate buffer), as well as a metal-free electrocatalyst synthesized by the same method. This phenomenon was further investigated using near-ambient pressure XPS, which evidenced that the preferential adsorption site for CO₂ was dependent of the metallic element nature: for Fe-N-C, the CO₂ preferentially adsorb on pyridinic and hydrogenated (pyrrolic) nitrogen moieties (see Figure 1), hence evidencing the key role played by said moieties in the reactivity of the M-N-C electrocatalysts for the CO₂RR.

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