Electrochemical Performance of Galvanically Displaced Noble Metal Nanoparticles Onto Electrosprayed Graphene/CNT Electrodes for Energy Storage Applications

Advanced lithium-ion batteries (LIB) and fuel cells demonstrate promise as the next generation energy storage and conversion (ESC) technologies for high power and energy density applications such as wearables and electric vehicles. Although LIB dominate the battery market (>90%) due to its reliability, long cycle life, and market maturity, different and more innovative ways to improve the chemistry of the electrode structure must be discovered in order to reduce the cost of materials, dendritic issues at the solid-electrolyte interphase (SEI) layer, and improve upon the limited anode capacity (graphite theoretical capacity 372 mAh g^-1 ). Fuel cells are also promising renewable energy sources due to their high energy densities and scalability. However, both LIB and fuel cells are limited by the three-dimensional (3D) materials that enable their enhanced electrochemical properties and catalytic performance. Carbon nanostructures exhibit ideal conditions for catalytic support through their electrical conductivity, strength, and stability under wide-ranging mechanical, thermal, and chemical conditions. Here two such nanostructures, graphene oxide (GO) and oxidized carbon nanotubes (Ox-CNTs), are synthesized into a supporting 3D network for high surface-area noble-metal nanoparticles. GO and Ox-CNTs were mixed with polyacrylic acid (PAA) as a binding agent and synthesized via air-controlled electrospray. Aqueous noble metal salt solutions (HAuCl₄, K₂PtCl₄, and Na₂PdCl₄) galvanically displaced onto the graphene oxide carbon nanotube (GO-CNT) three-dimensional (3D) network. A 3-D structure of carbon-nanomaterials with noble metal nanoparticles performance was characterized with Scanning Electron Spectroscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), and Raman spectroscopy. Electrochemical catalytic performance of the galvanically displaced noble metal nanoparticles were evaluated using linear sweep voltammetry (LSV) to determine the on-set potential for oxygen reduction reaction (ORR), minimum overpotentials of the catalyst necessary to drive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Results demonstrate that these structures lend themselves as a cost-efficient and scalable alternative to existing catalytic electrodes used in energy storage technologies such as lithium ion batteries, lithium-air batteries, and fuel cells. Overall, we found that the high surface area intercalation electrodes is electrochemically and kinetically driven through the synergy between the noble metals and the 3D graphene supported structure.