(390g) Ni-Fe Layered Double Hydroxides and Ni-Sulfide Electrocatalyst Foams for Electrochemical Energy Storage and Conversion Devices

Enoch A. Nagelli^1,2*, Caspar Yi^1,2, F. John Burpo^1,2, Sean P. Rogers¹, Matthew DiBiase¹, Jiangtian Li³, Rongzhong Jiang³, Deryn Chu^3*

¹Department of Chemistry & Life Science, Chemical Engineering Program, United States Military Academy, West Point, New York 10996

²Photonics Research Center, United States Military Academy, United States Military Academy, West Point, New York 10996

³U.S. Army Combat Capabilities Development Command, Army Research Laboratory, Sensors and Electron Directorate, 2800 Powder Mill Rd., Adelphi, MD 20783-1107

Electronic conductivity of porous electrodes by Faradaic and non-Faradaic charge transfer processes impact the energy and power densities and overall performance of electrochemical energy storage and conversion devices. Advances in three-dimensional (3D) porous electrode materials design offers a selection of cost-effective non-precious metal porous electrodes such as nickel for electrochemical energy applications. These alternative catalysts include nickel foams with high surface area and surface-to-volume ratio are promising materials to reduce kinetic losses and enhance mass transfer rates, respectively. Electrochemical devices such as fuel cells rely on electrolysis to produce hydrogen and oxygen gases with expensive porous catalysts. Supercapacitor performance is impacted by slow ion diffusion and lower conductivity through the porous electrodes. Transition metal layered hydroxides have been demonstrated to be conductive and feasible supercapacitor electrode materials with enhanced double-layer capacitance, as well as high performing fuel cell electrocatalysts [1-3]. In this study, we investigate the role of surface morphology, elemental composition, and crystal structure of Ni-Fe layered double hydroxide (LDH) and Ni-S based foams produced from electrodeposition and hydrothermal synthesis techniques on electrocatalysis for electrochemical anodic and cathodic water splitting reactions (hydrogen evolution reaction/HER and oxygen evolution reaction/OER). Electrocatalytic performance of the Ni-Fe LDH and Ni-S based 3D foams was evaluated using linear sweep voltammetry to determine the minimum overpotentials of the catalyst necessary to drive HER and OER. Moreover, galvanostatic charge-discharge cycling of the NiFe-LDH and Ni-S foams was conducted to determine the capacitance and overall performance as supercapacitor electrodes. Electrochemical impedance spectroscopy was used to determine the electronic and ionic conductivity of the hierarchical porous foams. Material characterization techniques such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and x-ray diffractometry (XRD) were used to characterize the surface morphology, surface elemental composition, and crystallinity, respectively.

KEYWORDS: Fuel Cells, Supercapacitors, 3D Foams, Electrocatalysis, Oxygen Evolution Reaction, Hydrogen Evolution Reaction, Electrochemical Engineering, Energy Storage

Corresponding Authors: Enoch A. Nagelli, Email: enoch.nagelli@westpoint.edu Deryn Chu, Email: deryn.d.chu.civ@mail.mil

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