In-situ electrochemical transformations of high-performance iron-nickel nanocarbide electrocatalysts for the oxygen evolution reaction

Amanda J. Ritz, Isabella A. Bertini, Julian A. Bazo, Samuel F. Wenzel, Geoffrey F. Strouse, Robert A. Lazenby

Florida State University

Iron-nickel (oxy)hydroxides (FeNiOOH) have recently emerged as some of the best candidates of electrocatalysts for alkaline water electrotrolysis, and therefore as means of efficient hydrogen generation. Less well-known non-oxide-based Fe-Ni catalysts can undergo electrochemical transformations that result in oxides or hydroxides on the nanoparticle surface, and leading to enhanced intrinsic activity. The dynamic surface reconstruction of non-oxide-based catalysts demands a greater understanding for detection of (metal hydroxide/(oxy)hydroxide) active sites. Herein, we rationally fabricated Fe_xNi_1-xC_y nanocarbides that were synthesized from a single-source precursor Prussian blue analogue (PBA), in which the molar proportion of Fe to Ni was controlled, allowing us to study the effect of Fe incorporation on the oxygen evolution reaction (OER) activity. High surface area metal carbides have precedence of exhibiting favorable bulk and surface properties, such as high conductivity, stability, and corrosion resistance, which are advantageous for in situ electrochemical tuning of an electrocatalyst. The effects of Fe incorporation and surface (oxy)hydroxide reconstruction for Fe_xNi_1-xC_y nanocarbides were investigated by determination of electronic properties, OER activity, and surface oxide species using x-ray photoelectron spectroscopy, voltammetric techniques, and Raman spectroscopy. Measurements of OER activity revealed amounts of Fe as low as 1% (in FeNiC) achieved a 200 mV reduction in overpotential. Our results have significant implications for enhanced understanding of the role of Fe and reconstructed surface oxide species for the rational design of highly active FeNi carbide (and non-oxide) OER electrocatalysts.