A novel tetragonal T-CN supported transition metal atoms as superior bifunctional catalysts for OER/ORR: From coordination environment to rational design.

Single-atom catalysts with particular electronic structures and precisely regulated coordination environments delivering excellent activity for oxygen-evolution reaction (OER) and oxygen-reduction reaction (ORR) are highly desirable for renewable energy applications. In this work, a novel tetragonal carbon nitride T-CN monolayer with remarkable stability was predicted by using the RG method. Inspired by the well-defined atomic structures and just right N aperture of T-CN substrate, the electrocatalytic performance of a series of transition metal single-atoms anchored on porous T-CN matrix (TM@CN) have been systematically investigated. In addition, machine learning (ML) method was employed with the gradient boosting regression GBR model to deeply explore the complex controlling factors and offer direct guidance for rational discovery of desirable catalysts. On this basis, the coordination environment of the central TM active sites has been tailored by incorporating heteroatoms. Impressively, the Co@CN/B-C, Rh@CN/SC and Rh@CN/SN exhibit significantly enhanced OER/ORR activity with notably low η/η of 0.39/0.32, 0.26/0.35 and 0.37/0.27 V, respectively. Our work provides insights into the rational design, data-driven, performance regulation, mechanism analysis and practical application of TMNC catalysts. Such a systematic theoretical framework can also be expanded to many other kinds of catalysts for energy storage and conversion.