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Summary: The extension of low‐expense and stable electrocatalysts for oxygen reduction reaction (ORR) is of importance to improve the performance of metal‐air batteries and fuel cells. In this work, we unravel the ORR electrocatalytical mechanisms on a series of transition metal atom‐doped on the defect graphene (TM@sv‐graphene) by carrying out spin‐polarized first‐principles computations. The formation energy of the TM@sv‐graphene, which is related to its stability, along with the binding energy of O2, OOH, 2OH, OH, and O species are evaluated. The calculations of Gibbs free energy show that two different pathways, O* mechanism and 2OH* mechanism, of ORR compete with each other based on the structures of intermediates (OOH, 2OH, OH and O). It is found that Co, Rh, Ir, Pt, and Mn@sv‐graphene favor the O* mechanism while Ag, Au, Cd, Cu, Zn, Fe, Ni, Pd, Sc, Cr, Ti, Zr, and V@sv‐graphene strongly promote the 2OH* mechanism. The overpotential (η) of the ORR is predicted and can be a valid descriptor that manifests the catalytic activity of different TM@sv‐graphene. Among these catalysts, the Pd@sv‐graphene (η = 1.20 V) exhibits the best activity for the ORR. The results provide new insight into electrochemical mechanism of ORR for novel single‐atom electrocatalyst. [ABSTRACT FROM AUTHOR]

We performed a systematic study of carbon monoxide oxidation on the nitrogen-doped penta-graphene by utilizing spin-polarized density functional theory calculations. The possible reaction pathways via both Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms were illustrated. The results manifest that the nitrogen-doped penta-graphene displays very high catalytic activity and is more competitive with many metal-based and carbon-based catalysts for low-temperature CO oxidation by reason of the very small energy barrier of the rate-limiting step (there is no activation energy for the ER mechanism and only 0.33 eV for the LH mechanism). This study opens a new avenue for the design of 2-D graphene-based materials and provides valuable clues for developing catalytic activity carbon materials for low-temperature CO oxidations. [ABSTRACT FROM AUTHOR]

We systematically investigate electrocatalytic activity and NH 3 selectivity of a single-atom catalyst supported on graphitic carbon nitride for nitrate reduction reaction (NO 3 RR) using first-principles calculations. Our results reveal Ti/g-C 3 N 4 , V/g-C 3 N 4 , and Nb/g-C 3 N 4 serve as the most promising NO 3 RR catalysts, as they exhibit excellent activity, high selectivity, and low limiting potential. [Display omitted] • Electrocatalytic activity and NH 3 selectivity of single-atom catalysts for nitrate reduction reaction has been explained. • This work reveals the structure dependence of NO 3 RR reaction pathways in single-atom catalysts. • Ti/g-C 3 N 4 , V/g-C 3 N 4 , and Nb/g-C 3 N 4 serve as the most promising NO 3 RR catalysts with excellent activity, high selectivity and low limiting potential. Electroreduction of water-pollutant nitrate to valuable ammonia provides a green and efficient route for low-temperature NH 3 production instead of the convention Haber-Bosch process. However, finding robust catalysts for achieving nitrate to ammonia conversion remains a challenge due to the lack of a mechanistic view on the highly complex nitrate reduction and NH 3 selectivity. Herein, we systematically investigate electrocatalytic activity and NH 3 selectivity of a single-atom catalyst supported on graphitic carbon nitride (TM/g-C 3 N 4) for nitrate reduction reaction (NO 3 RR) using first-principles calculations. Our results reveal that Ti/g-C 3 N 4 , V/g-C 3 N 4 , and Nb/g-C 3 N 4 serve as the most promising NO 3 RR catalysts, as they exhibit stability, excellent activity, high selectivity (Faradaic efficiency of ∼ 100%), and low limiting potential (−0.42, −0.25, and −0.40 V for Ti/g-C 3 N 4 , V/g-C 3 N 4 , and Nb/g-C 3 N 4, respectively). In addition, considerable potential energy barriers are found in the formation of byproducts NO 2 , NO, and N 2 O, validating their high selectivity. Nitrate to ammonia conversion is more competitive than hydrogen evolution reaction on TM/g-C 3 N 4 owning to a lower limiting potential. This work reveals the structure dependence of NO 3 RR reaction pathways in single-atom catalysts and opens a new avenue for designing more efficient catalysts for NO 3 RR under ambient conditions. [ABSTRACT FROM AUTHOR]