Selectivity trends in two-electron oxygen reduction: insights from two-dimensional materials

Abstract

Advancing the discovery of novel materials for electrosynthesis of hydrogen peroxide (H₂O₂) via the two-electron oxygen reduction reaction (2e-ORR) while rationalizing and quantifying selectivity trends has been an ambitious objective. A recently introduced selectivity descriptor, ΔΔG, published in Chem Catal. 2023, 3(3), 100568, utilizes thermodynamic analysis of adsorption free energies of key ORR intermediates (ΔG_OOH* and ΔG_O*) along with the free energy of H₂O₂ to quantify selectivity and establish trends. This model has been successfully applied to a large database of binary alloys, demonstrating strong potential for predicting selective materials Angew. Chem. Int. Ed. 2024, 63, e202404677. In this study, we systematically explore a diverse range of active sites in carbon-based structures, boron nitrides, and single atom catalysts, emerging classes of materials for 2e-ORR. We assess the effectiveness of ΔΔG in capturing selectivity trends and distinguishing sites that are both catalytically active and highly selective. Our findings highlight that not all active sites in carbon-based materials reported with high activity inherently exhibit high selectivity, with only a small fraction meeting both criteria. This work highlights the importance of ΔΔG as a predictive tool, providing valuable insights for designing selective and active two-dimensional materials.