Simultaneously Achieving High Activity and Selectivity toward Two-Electron O2 Electroreduction: The Power of Single-Atom Catalysts

On-site production of hydrogen peroxide (H2O2) using electrochemical methods could be more efficient than the current industrial process. However, due to the existence of scaling relations for the adsorption of reaction intermediates, there is a long established trade-off between the activity and selectivity of the catalysts, as the enhancement of catalytic activity is typically accompanied by a four-electron O2 reduction reaction (ORR), leading to the reduced selectivity for the H2O2 production. Herein, by means of density functional theory (DFT) computations, we reported the feasibility of several classes of important and representative experimentally achievable single-atom catalysts (SACs) toward two-electron ORR, paying attention to their stability, selectivity, and activity at the acidic medium. Starting from 210 two-dimensional (2D) SACs, we demonstrated that 31 SACs have the potential to break the metal-based scaling relations and simultaneously achieve high activity and selectivity toward H2O2 production and screened out 7 SACs with higher activity than the PtHg4 in acidic media. Especially, a noble metal-free SAC, namely, a single Zn atom centered phthalocyanine (Zn@Pc-N4), has a remarkable activity improvement with a small overpotential of 0.15 V. Moreover, using multivariable analysis and machine-learning techniques, we provided a comprehensive understanding of the underlying origin of the selectivity and activity of SACs and unveiled the intrinsic correlations between structure and catalytic performance. This work may pave a way to the design and discovery of more promising materials for H2O2 production.