Atomically Thin Film Platinum Supported Sub-Stoichiometric Titania: A Tunable Electrocatalyst for Fuel Cell Reactions

Abstract

Designing efficient catalyst for fuel cell devices has gained an increasing amount of attention over the last decade for chemical to electrical energy conversion. The widespread commercialization of fuel cells, such as proton exchange membrane fuel cells, are hindered by the sluggish kinetics of the cathodic oxygen reduction reaction, the costly platinum catalyst employed within the cell, along with long-term catalyst degradation. One approach aimed at simultaneously addressing these drawbacks is to synthesize atomically thin film platinum on a robust support. While many catalysts are being investigated for fuel cell reactions, Pt based catalysts are in high demand due to stability, high activity, and low overpotential. We demonstrate an unprecedented electrochemical deposition of Pt on graphene/sub-stoichiometric titania supports (Ti2O3 and Ti3O5).Ti2O3 and Ti3O5 films were deposited on silicon wafers via pulsed laser deposition. Four-point probe measurements, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), ultraviolet photoelectron spectroscopy (UPS), and Scanning Electron Microscopy (SEM) were used to examine the chemical, electrical, and morphological properties of the sub-stoichiometric supports. Chemical vapor deposited graphene on copper foil was transferred through a series of etchants to produce the Gr/TixO2x-1 (x=1 or 2) support. Incorporating a graphene interfacial layer between Pt and TixO2x-1 served as a platform for large-area, fully wetted growth of two-dimensional Pt films. Pt thin films were electrochemically co-deposited on Gr/TixO2x-1 supports in an aqueous solution consisting of Pt2+ and Cu2+.The chemical and morphological properties of the electrochemically deposited Pt films were investigated using XPS and SEM, respectively. Pt films were found to exist in a metallic state. The functionality of the synthesized catalyst was tested using major fuel cell reactions including, oxygen reduction, methanol oxidation, and ammonia oxidation reactions. Overall, varying the stoichiometry of the TixO2x-1 supports leads to reaction overpotential tunability as predicted by fluctuations in the work-function of the support. This study provides insights on the preparation of a novel Pt/Gr/TixO2x-1 catalyst aimed at developing clean energy devices.