Improved borohydride oxidation kinetics on Au-based MOFs and their suitability as anodes for borohydride fuel cells

Title : Improved borohydride oxidation kinetics on Au-based MOFs and their suitability as anodes for borohydride fuel cells

Abstract:

Researchers are investigating direct liquid fuel cells (DLFCs) as alternatives to typical proton-exchange membrane fuel cells because of their higher energy density and ease of storing and transporting liquid 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. 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 the borohydride oxidation reaction (BOR) in DBFCs. 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. The present study evaluated the performance of newly developed Au-MOF-based electrocatalysts with different functional groups for DBFCs. Specifically, six MOF-based materials were synthesized and analyzed for their catalytic activity for 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, suggesting the enhancement of the catalytic activity from the presence of the –NH₂ functional group. 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 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 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 DLFC types.

Biography:

Ines Belhaj is a Chemical Engineer with a master’s degree, currently pursuing a Ph.D. in the same field at IST, Lisbon University. She joined Prof. Diogo Santos and Vitor Geraldes’s group in 2022 to develop electrodes and membranes for direct liquid fuel cells. In addition, Ines has experience as a quality system analyst in the pharmaceutical industry, where she developed strong organizational skills, attention to detail, and team contribution abilities. Ines is highly motivated to excel in her work and continue learning and growing.