Simultaneously Achieving High Activity and Selectivity toward Two-Electron O 2 Electroreduction: The Power of Single-Atom Catalysts

On-site production of hydrogen peroxide (H 2 O 2 ) 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 O 2 reduction reaction (ORR), leading to the reduced selectivity for the H 2 O 2 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 H 2 O 2 production and screened out 7 SACs with higher activity than the PtHg 4 in acidic media. Especially, a noble metal-free SAC, namely, a single Zn atom centered phthalocyanine (Zn@Pc-N 4 ), 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 H 2 O 2 production.