Overcoming Site Heterogeneity In Search of Metal Nanocatalysts.

Site heterogeneity of metal nanocatalysts poses grand challenges for catalyst design from first principles. To accelerate catalyst discovery, it is of pivotal importance to develop an approach that efficiently maps catalytic activity of nanoparticles onto geometry-based descriptors while considering the geometric strain and metal ligand of an active site. We demonstrate that there exist linear correlations between orbitalwise coordination numbers CNα and free formation energies of oxygen species (e.g., *OH and *OOH) at Pt sites. Kinetic analysis along with herein developed structure-activity relationships accurately predicts the activity trend of pure Pt nanoparticles (∼1-7 nm) toward oxygen reduction. Application of the approach to a search of Pt nanoalloys leads to several Pt monolayer core-shell nanostructures with enhanced oxygen reduction activity and reduced cost. The approach presented here facilitates a transition from traditional single-crystal models to nanoparticles in theory-guided catalyst discovery.

Unifying the 2e(-) and 4e(-) Reduction of Oxygen on Metal Surfaces.

Understanding trends in selectivity is of paramount importance for multi-electron electrochemical reactions. The goal of this work is to address the issue of 2e(-) versus 4e(-) reduction of oxygen on metal surfaces. Using a detailed thermodynamic analysis based on density functional theory calculations, we show that to a first approximation an activity descriptor, ΔGOH*, the free energy of adsorbed OH*, can be used to describe trends for the 2e(-) and 4e(-) reduction of oxygen. While the weak binding of OOH* on Au(111) makes it an unsuitable catalyst for the 4e(-) reduction, this weak binding is optimal for the 2e(-) reduction to H2O2. We find quite a remarkable agreement between the predictions of the model and experimental results spanning nearly 30 years.