First-Row Transition Metal Nanowires As Electrocatalysts for the Oxygen Reduction and Oxygen Evolution Reactions

Abstract

Platinum is an effective catalyst for the electrochemical reactions in fuel cells and sensors but its high cost and low abundance has prevented the wide-spread commercial use of these devices. As a result, it is critical to develop electrocatalysts with other abundant and catalytically active transition metals. First-row transition metals represent a promising alternative because of their low cost and high abundance, however they are not sufficiently stable to act as catalysts in acidic media. Recent advancements in membrane technology have enabled the creation of electrochemical devices that can operate in alkaline conditions, where first row transition metals and their oxides are stable. In this project, we use a solution-based synthetic method to prepare metal nanowires consisting of two or more first-row transition metals, wherein the composition can be easily and predictably controlled. The nanowires are characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The resulting nanowires are catalytically active toward the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in alkaline media. Our results indicate that the catalytic activity is highly dependent on the composition of the nanowires and the activity can be tuned to increase the ORR activity significantly beyond that of nanowires consisting of only a single element. In addition, Pt-free transition metal alloy nanowires display significantly enhanced performance beyond that of pure Pt when used as catalysts for OER.