Next generation catalysts for the oxygen reduction reaction aim to minimize precious metal loading while circumventing performance limitations imposed by the Sabatier volcano plot. Catalytic architectures have evolved from using Pt-alloys, to monolayered Pt films supported on carbides/nitrides and single metal atom catalysts embedded in carbon supports. Using density functional theory calculations, we demonstrate how tailoring catalytic environments beyond the binding site for supported metal catalysts and single-site catalysts boosts their performance for the 2e- and 4e- oxygen reduction reaction. We first elucidate how the electronic metal support interaction between the carbide/nitride support and metal monolayers enhances the binding energies of oxygenate species. These interactions lead to exquisitely tunable binding strengths of catalytic descriptors like OH*, through changes in the support composition or the support termination. These metal-support interactions result in Ag and Au monolayers supported on carbides/nitrides having lower overpotentials than Pt (111), thus expanding the range of metals to compositions beyond Pt. Using theoretical constructs like scaling relations between adsorption energies, we elucidate how the design principles for the oxygen reduction reaction are different for supported metal catalysts as compared to the more traditional unsupported metal systems. By screening over 200+ metal overlayers on carbides and nitrides, we find 10+ overlayers that yield a lower overpotential than Pt (111), while being thermodynamically stable under electrochemical conditions. These systems include Ag/N-terminated NiN (111), Au/C-terminated VN (111), and Pt/Ni-terminated NiN (111). In a second study, we describe how tuning non-covalent interactions beyond the binding site increases the selectivity for the two-electron oxygen reduction reaction to H2O2. Experimental results indicate that aminoanthraquinone adsorbed on single site catalysts embedded in nitrogen doped carbon supports increases the faradaic efficiency to H2O2. First principles calculations reveal that this increase in faradaic efficiency is caused by weakened adsorption of oxygenate species within a 3.5 A nanochannel between aminoanthraquinone and the carbon supports. Taken together, these two studies illustrate how modulating charge transfer and tuning non-covalent interactions beyond the binding site enhances reactivity metrics of the oxygen reduction reaction.

Enhancing the selectivity of oxygen reduction electrocatalysts by tailoring catalytic environments beyond the binding site

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