Computational design of single-atom catalysts embedded on reduced graphitic carbon nitride monolayers

The design of efficient single-atom catalysts (SACs) with optimal activity and selectivity for sustainable energy and environmental applications remains a challenge. In this work, comprehensive first-principles calculations are performed to validate the feasibility of single TM atoms (3d, 4d, and 5d series) embedded in two different conformations of graphitic carbon nitride (g-C3N4) monolayers. Additionally, we investigate the effect of nitrogen vacancies in the g-C3N4 monolayers on the absorption of SACs considering three potential absorption scenarios that correspond to different experimental conditions. Our results point to the most stable configurations with the lowest formation energies and indicate that the absorption of single TM atoms on-vacancy and on-center sites are more favorable than via-substitution. In addition to the thermodynamic stability, electrochemical stability is also investigated through the calculation of the dissolution potential of the SACs. Within the scenarios considered in this study, we find that Pt, Pd, Rh, Au, Ru, Ir, Cu, Co, Fe, and Ni will produce the most robust SACs on both (edge and bridge) N vacancy site of reduced g-C3N4. Our findings provide guidance for the design and development of g-C3N4 sheets decorated with single TM atoms for technological applications such as pollutant degradation, CO2 reduction, N2 fixation, selective oxidation, water splitting, and metal ion-based batteries.