N/O coordinated s-block potassium atoms as highly active sites for electroreduction of CO2 to CO

Abstract

According to the d-band center theory of transition-metals, s-block main group metals with fewer valence electrons and delocalized s/p-orbitals are considered to exhibit poor electrocatalytic activity. Therefore, single-atom catalysts (SACs) for CO₂ electroreduction to CO primarily focus on transition metal and p-block main group metal atoms as active centers. Herein, we prepared a porous carbon material doped with N/O coordinated K atoms using a simple high-temperature solid-phase synthesis method. The synthesized K–N, O/C catalyst demonstrates remarkable CO selectivity with Faraday efficiency (FE) exceeding 90% over a wide potential window between −0.5 V and −0.9 V versus the reversible hydrogen electrode (vs. RHE). Moreover, the catalyst exhibits a maximum FE of 97.8% towards CO at −0.6 V vs. RHE. In situ attenuated total reflectance infrared spectroscopy (ATR-FTIR) confirms the formation of *COOH on the K–N, O/C catalysts. Through Density Functional Theory (DFT) calculations, we screen out the most possible coordination structures. The K–O₂ and K-pyrrolic-N₂ models show significantly high CO₂ reduction activity. Heteroatom doping induces partial overlap of the electronic states of the s and p orbitals of the K atom with the p orbitals of the coordinated O atom or N atom, thus modulating the electronic structure of the K atom into the catalytically active center for the conversion of CO₂ to CO.