Synthesis of Nanocatalysts with Non-Precious Metals for Efficient Oxygen Evolution Reaction (OER) Catalysis

Abstract

Efficient ways to perform electrolysis of water to form hydrogen and oxygen gas has far reaching consequences regarding in the energy sector. Hydrogen is considered to be fuel alternative to fossil fuels and electrolysis is regarded as a large-scale storage option for renewable energy as chemical fuels from sources such as wind and solar. In the electrolysis of water, the oxygen evolution reaction (OER) is the rate-limiting step and thus provides multiple opportunities to improve overall performance. Development of electrocatalysts with low overpotential, low Tafel slope, high mass activity, and high turn-over frequency (TOF) in alkaline medium that will expedite the reaction is crucial. Non precious metals such as iron, nickel, and cobalt may be the solution to the slow kinetics of the OER. In recent literature, bimetallic nanowires with these three metals have shown promising results. Nanowires can be synthesized using a simple hydrothermal process which is amenable to large scale production. Yang et al. have synthesized NiCoO2 nanowires with a small overpotential (~0.303 V) at a current density of 10mA cm-2 and low Tafel slope (~57 mV dec- 1).1 Fang et al. have synthesized NiCoS2 nanowires with small overpotential (~0.27V) to afford a current density of 10mA cm-2 and a low Tafel slope (~119mV dec-1).2 Recent work on bimetallic layered double hydroxide (LDH) nanoparticles have also yielded positive results. Zhu et al. fabricated a novel NiFe-LDH/nanocarbon hybrid with small overpotential (~0.35V) at a current density of 10mA cm-2 and a low Tafel slope (~54mV dec-1).3 Li et al. developed NiFe-LDH array with a small overpotential of (~0.224V) at a current density of 10mA cm-2.4 This research will build on these recent published work with a focus on synthesizing nanoparticles and nanowires with an optimal ratio of metals, as the ratio of metals in a multimetallic nanostructure is likely to factor heavily in the electrochemical activity. Our research will also attempt to identify preferred nanocatalyst candidates for electrocatalyst performance in alkaline solution. In this presentation, we will report on our work thus far in comparing the electrochemical performance and material characterization of nanocatalysts synthesized with different metal compositions, as well as comparing nanoparticle morphology to nanowire morphology. Imaging techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) will be used to study the morphology of the particles. Elemental analysis and characterization of nanocatalyst phase and surface chemistry will be performed using energy dispersive x-ray spectroscopy (EDX), x-ray photoelectron spectroscopy (XPS), and powder x-ray diffraction (XRD). Electrochemical analysis using cyclic voltammetry will also be performed on the bimetallic nanomaterials. Experiments on the stability of the materials will also be conducted using chronoamperometry.