The urgent need for artificially fixing CO calls for catalysts of high efficiency. The transition metal functionalized porphyrin (TMP) is one of the most important types of organic catalysts for CO reduction. However, the catalytic mechanisms of TMP in CO reduction still remain controversial. Starting from the previously neglected catalyst self-protonation model, we uncover a new CO reduction mechanism on cobalt-porphine, which involves an indirect proton transfer step occurring at the beginning of the reduction cycle. Based on this protonation mechanism, we demonstrate the different correlations between producing rate and pH for the formation of CO and methane, in good agreement with available experimental observations. Our results reveal how pH and potential affect the CO reduction process, providing important clues and insights for further optimization of TMP catalysts.

We propose an effective method to accurately determine the defect formation energy E f and charge transition level ε of the point defects using exclusively cohesive energy E coh and the fundamental band gap E g of pristine host materials. We find that E f of the point defects can be effectively separated into geometric and electronic contributions with a functional form: E f = χE coh + λE g , where χ and λ are dictated by the geometric and electronic factors of the point defects (χ and λ are defect dependent). Such a linear combination of E coh and E g reproduces E f with an accuracy better than 5% for electronic structure methods ranging from hybrid densityfunctional theory (DFT) to many-body random-phase approximation (RPA) and experiments. Accordingly, ε is also determined by E coh /E g and the defect geometric/electronic factors. The identified correlation is rather general for monovacancies and interstitials, which holds in a wide variety of semiconductors covering Si, Ge, phosphorenes, ZnO, GaAs, and InP, and enables one to obtain reliable values of E f and ε of the point defects for RPA and experiments based on semilocal DFT calculations.