Metal-Free N, P-Codoped Carbon for Syngas Production with Tunable Composition via CO Electrolysis: Addressing the Competition Between CO Reduction and H Evolution.

Electroreduction of carbon dioxide into value-added fine chemicals is a promising technique to realize the carbon cycle. Recently, metal-free heteroatom doped carbons are proposed as promising cost-effective electrocatalysts for CO reduction reaction (CORR). However, the lack of understanding of the active site prevents the realization of a high-performance electrocatalyst for the CORR. Herein, we synthesized metal-free N, P co-doped carbons (NPCs) for producing syngas, which is composed of H and CO, by CO electrolysis using inexpensive bio-based raw materials via simple pyrolysis. The syngas ratio (H/CO) can be controlled within the high demand range (0.3-4) at low potentials using NPCs by tuning the N and P contents. In comparison with only N doping or P doping, N and P co-doping has a positive impact on improving CORR activity. Experimental analysis and density functional theory (DFT) calculations revealed that negatively charged C atoms adjacent to N and P atoms are the most favorable active sites for CO-to-CO conversion compared to pyridinic N on N, P co-doped carbon. Introducing N atoms generates the preferable CO adsorption site, and P atoms contribute to decreasing the Gibbs free energy barrier for key *COOH intermediates adsorbed on the negatively charged C atoms.