Au-Based MOFs as Anodic Electrocatalysts for Direct Borohydride Fuel Cells

Abstract

Researchers are exploring direct liquid fuel cells (DLFCs) as alternatives to proton-exchange membrane fuel cells because of their higher energy density and ease of storing and transporting the fuel. Direct borohydride fuel cells (DBFCs) are of particular interest as they offer a sustainable energy source with their high-power density output and the use of a highly alkaline NaBH4 medium [1]. Ensuring efficient and cost-effective catalysts for DBFCs is crucial for their commercial viability. Metal-organic frameworks (MOFs) have demonstrated significant potential as anodic electrocatalysts for BOR in DBFCs [2]. However, research should explore various modifications to MOFs, such as the incorporation of alternative metal ions or functional groups, to improve their catalytic efficiency and reduce cost. This study evaluated the performance of newly developed MOF-based electrocatalysts for DBFCs. Specifically, six MOF-based materials were synthesized and analyzed for their ability to facilitate borohydride oxidation (BOR) using cyclic voltammetry and chronoamperometry in alkaline media. MIL-101_Au@NH2 and MOF-808_Au@NH2 were found to be highly effective for BOR. The kinetic parameters for BOR with MOF-based electrocatalysts, including activation energy, reaction order, exchanged electrons, and anodic charge transfer coefficient, were determined. The activation energy for BOR was found to be 13.6 kJ mol−1 and 15.3 kJ mol−1 for MIL-101_Au@NH2 and MOF-808_Au@NH2, respectively. The number of transferred electrons, n, was found to be 7.0 and 3.1 for MIL-101_Au@NH2 and MOF-808_Au@NH2, respectively. This study demonstrates that MOF-based electrocatalysts can enhance DBFCs' performance, while offering insight into the potential usage of MOFs in other fuel cell technologies.[1] B. Šljukić, D.M.F. Santos, "Direct borohydride fuel cells", in: "Direct Liquid Fuel Cells: Fundamentals, Advances, and Future", 1st ed., R.G. Akay, A.B. Yurtcan (eds.), Academic Press, USA, 203-232 (2021)[2] G. Backovic, B. Šljukić, G.S. Kanberoglu, M. Yurderi, A. Bulut, M. Zahmakiran, D.M.F. Santos, Ruthenium (0) nanoparticles stabilized by the metal-organic framework as an efficient electrocatalyst for borohydride oxidation reaction, International Journal of Hydrogen Energy, 45, 27056-27066 (2020).