(617gr) Au@MxOy Core-Shell Nanoparticles As Catalysts for the Oxygen Evolution Reaction

One of the most imperative challenges facing society today is the development of a sustainable energy economy. While renewable energy sources such as solar and wind can provide more than enough energy to meet current and projected global demand, the intermittency of these sources is problematic. A promising strategy to mitigate this intermittency issue is to convert and store energy in the form of chemical bonds. Electrochemical water splitting is one such promising method in which renewable energy is converted into a storable, high purity, carbon-free hydrogen fuel. Unfortunately, the anodic oxygen evolution reaction (OER) in electrolyzer devices suffers from slow kinetics. In alkaline conditions, first row transition metals have shown high activity and stability for the OER, however, high overpotentials are still required.[1] Therefore, before electrolyzers can become industrially feasible solutions, high activity, device-ready catalysts for the OER must first be developed.

Recently, Au has been found to have beneficial effects on the activity of transition metal catalysts for the OER. Firstly, Au can alter catalyst electronic structure and allow access to higher activity metal oxide phases as was observed for the Au/Mn-oxide system.[2] Additionally, it has been postulated that Au can reduce overpotential requirements for Mn and Co oxides by participating directly in the OER mechanism.[3] In a recent report, Au was also found to enhance the activity of NiCe based catalysts.[4] Lastly, as a high conductivity support, Au can increase the conductivity of insulating metal oxide materials whose high intrinsic activity is thwarted by poor electronic properties.[5] Capitalizing on these beneficial effects, the Au-core metal oxide-shell nanoparticle structure has the potential to achieve enhanced activity in a device-ready form. This nanostructure also provides an increased number of active sites and greater material utilization than thin films and can achieve higher metal loadings without hitting conductivity limitations.

Herein we present the synthesis, characterization and electrochemical performance of Au-core metal oxide-shell (Au@M_xO_y) nanoparticles as OER electrocatalysts. Single metal and alloy oxide nanoparticles with and without Au cores were synthesized with high uniformity via wet chemical methods. Particle morphology and composition were analyzed using transmission electron microscopy (TEM), scanning TEM energy dispersive spectroscopy (STEM-EDS), scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS). Electrochemical activity and stability were evaluated in a three electrode rotating disk arrangement in Fe-free conditions for non-Fe based catalysts.[6] The effect of the Au core is evaluated and catalyst performances are compared.