Coordination environments build up and tune a superior synergistic genome toward novel trifunctional (TM-NxO4-x)@g-C16N3-H3: High-throughput inspection of ultra-high activity for water splitting and oxygen reduction reactions

Emerging as a prominent area of focus in energy conversion and storage technologies, the development of highly active metal based single-atom catalysts (SACs) holds great significance in searching alternatives to replace precious metals toward the efficient, stable, and low-cost hydrogen evolution reaction (HER), as well as the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Combining the tremendous tunability of ligand and coordination environment with rich metal-based electrocatalysts can create breakthrough opportunities for achieving both high stability and activity. Herein, we propose a novel and stable holey graphene-like carbon nitride monolayer g-C16N5 (N-4@g-C16N3) stoichiometries interestingly behaving as a natural substrate for constructing SACs ((TM-N-4)@g-C16N3), whose evenly distributed holes map rich and uniform nitrogen coordination positions with electron-rich lone pairs for anchoring transition metal (TM) atoms. Then, we employed density functional theory (DFT) calculations to systematically investigate the electrocatalytic activity of (TM-N-4)@g-C16N3 toward HER/OER/ORR, meanwhile considering the synergistic modulation of H-loading and O-coordination ((TM-NXO4-X)@g-C16N3-H-3, X = 0-4). Together a four-step procedure screening mechanism with the first-principles high-throughput calculations, we find that (Rh-N-4) and (Ir-N2O2-II) distributed on g-C16N3-H-3 can modulate the adsorption strength of the adsorbates, thus achieving the best HER/OER/ORR performance among 216 candidates, and the lowest overpotential of 0.098/0.3/0.46 V and 0.06/0.48/0.45 V, respectively. Additionally, the d-band center, crystal orbital Hamilton population (COHP), and molecular orbitals are used to reveal the OER/ORR activity source. Particularly, the Rh/Ir-d orbital is dramatically hybridized with the O-p orbital of the oxygenated adsorbates, so that the lone-electrons incipiently locate at the antibonding orbital pair up and populate the downward bonding orbital, allowing oxygenated intermediates to be adsorbed onto (TM-N-4)@g-C16N3 -H-3 appropriately.

Automated summary

This study proposes a novel and stable holey graphene-like carbon nitride monolayer as a natural substrate for constructing highly active metal-based single-atom catalysts (SACs). Through density functional theory (DFT) calculations, the electrocatalytic activity of the SACs towards hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is systematically investigated. The study identifies specific catalysts that exhibit the best performance among 216 candidates, with the lowest overpotential.