Electrochemical Kinetics and Performance Characterization of Graphene Oxide-Carbon Nanotube-Noble Metal Custer Electrodes for Energy Storage Applications

As the consumer electronics, renewable energy, and electric vehicle markets have become integral to society, so have the energy store and conversion (ESC) technologies that enable them. The most versatile of these applications are lithium-ion batteries (LIBs) and hydrogen fuel cells (HFCs). The former of which have become ubiquitous due to their energy density, reliability, and cycle life while the latter deliver scalable and sustainable power with high energy density. Despite this, the need for further for high power and energy density drive demand for improvements in the materials chemistry in both technologies. However, the kinetics of the reactions that drive HFCs are limited by the chemistry and structure of the catalyst material. Moreover, LIBs suffer from dendrite formation in the solid-electrolyte interface layer and electrode materials with relatively low specific capacity (graphite anodes with specific capacity of 372 mAh g^-) in widespread usage. Structured carbon nanomaterials offer an alternative with ideal 3D properties for catalysis, improvements in battery performance, mechanical, chemical, and thermal stability. However, their synthesis is often lengthy, expensive and difficult to scale. Here, graphene oxide (GO) and oxidized Carbon nanotubes (ox-CNTs) are synthesized into a 3D carbon network. Then, mixed with 5 wt % polyacrylic acid (PAA) as a binder, they are air-controlled electrosprayed onto copper foil. High surface area noble metal (NM) nanoclusters are nucleated through the 3D carbon structure utilizing a spontaneous galvanic reduction reaction with NM salt solutions (K₂PtCl₄, and Na₂PdCl₄). The resulting 3D electrode structure of the GO/CNT-NM materials were characterized using Raman Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive X-Ray Spectroscopy. The on-set potential of the material as a catalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in hydrogen fuel cells were determined using linear sweep voltammetry (LSV). The electrochemical surface area and the redox potentials were verified using cyclic voltammetry (CV). Further, GO/CNT-NM electrodes were assembled into coin cell LIB half cells and characterized via electronic impedance spectroscopy (EIS). The GO/CNT-NM materials function as bifunctional catalytic electrodes, showcasing efficacy for catalysis in HFCs and improved specific capacity in LIBs. This improvement in kinetics and electrochemical performance is attributed to the coaction between the noble metal nanoclusters and the 3D GO/CNT network.