Anode Catalysts for Direct Hydrazine Fuel Cells: From Laboratory Test to an Electric Vehicle

Abstract

Novel highly active electrocatalysts for hydrazine hydrate fuel cell application were developed, synthesized and integrated into an operation vehicle prototype. The materials show in both rotating disc electrode (RDE) and membrane electrode assembly (MEA) tests the world highest activity with peak current density of 16 000 A g À1 (RDE) and 450 mW cm À2 operated in air (MEA).The automotive world will be changed in 2015, when leading manufacturers will publicly introduce their first generation of commercial fuel cell vehicles. It should be noticed, however, that these automobiles were developed with proton exchange membrane (PEM) technology and membrane electrode assemblies (MEAs) in fuel stacks containing platinum catalysts for both hydrogen oxidation and oxygen reduction.There are several drawbacks of PEM-based technology, including: the high cost of fuel cell membranes, the extremely high cost of platinum, and the absence of a developed hydrogen infrastructure. Further, the use of hydrogen requires a high-pressure tank, which requires a full redesign of the automobile frame. These factors result in a high-cost commercial vehicle with a low driving range and safety issues.In contrast to PEM hydrogen fueled vehicles development, researchers from Daihatsu Motor Co. have introduced the idea of anion-exchange membrane fuel cell with liquid fuels. [1][2][3][4][5][6][7][8][9][10][11] Switching from acidic proton exchange to alkaline, anion-exchange membranes has many benefits, including: 1) fast fuel oxidation and oxygen reduction and 2) possible use of cheaper non-platinum group metal catalysts as anode and cathode material for both sides of the MEA. The liquid fuel of choice was hydrazine hydrate, which has no carbon atoms and thus will not contribute to increased CO 2 levels, the theoretical electromotive force is 1.56 Vand it can be oxidized by number of cheap catalysts. [12] To meet the power output requirements of a stack with limited size, the anode material should provide the highest power density, be stable, and selective toward the production of water and nitrogen with no ammonia (NH 3 ) generation. Up to now, catalysts reported had a low activity with operation in air (real vehicles operation conditions).Herein we report the synthesis of novel Ni-based supported catalysts by a completely solvent-free method. The method is based on a mechanochemical approach and is scalable to hundreds of kilograms of catalyst and can be considered a "green" synthesis method compared with conventional synthesis, which requires the use of solvents. These catalysts show high activity in both rotating disc electrode (RDE) and MEA tests, with real vehicles operation conditions. The effects of catalysts loading and carbon addition on hydrazine electrooxidation were studied on nickel-based materials for the first time.These electrocatalysts for hydrazine electrooxidation were synthesized by solvent-free impregnation of nickel and zinc precursors by using a high-energy mechanochemical approach. The synthesized materials were compreh...

Superaerophobic graphene nano-hills for direct hydrazine fuel cells

“…1 Hydrazine as a liquid fuel for direct liquid fuel cells outshines others not only because of its high theoretical cell voltage (+1.61 V) but also due to its greater energy and power density compared with other fuels, especially hydrogen, which has traditionally been a standard due to its widespread use in various fuel-cell technologies. 2 However, the practical energy conversion efficiencies of hydrazinebased direct liquid fuel cells are lower than their theoretical values, mostly due to the requirement of a substantial overpotential for hydrazine oxidation; hence, an electrocatalyst is normally needed. So far, platinum is considered to be the best electrocatalyst for hydrazine oxidation with the lowest onset potential, but its price and scarcity pose serious challenges for its widespread use in commercial applications.…”

Effects of Pd Nanoparticle Size and Solution Reducer Strength on Pd/C Electrocatalyst Stability in Alkaline Electrolyte

“…16,17 These two advantages reduce the economic impact of the DLAFC technology, as recently demonstrated for direct hydrazine hydrate fuel cells. [18][19][20] Nevertheless, research in DLAFC has mainly been carried out to satisfy the criteria of a high initial catalytic activity; 18,[20][21][22][23][24][25][26] as such, it has (unfortunately) not been followed by a significant effort in the characterization of the electrode materials stability in alkaline medium. In fact, a sort of implicit consensus does exist on the supposedly larger stability of the catalysts in alkaline medium compared to acidic conditions, which essentially originates from the wider potential stability window of most metal elements (or their oxides) at high than low pH, as predicted by Pourbaix.…”

High Performance Platinum Group Metal-Free Cathode Catalysts for Microbial Fuel Cell (MFC)

“…46,47 The catalysts were all prepared using sacrificial support method (SSM) technique in which highly porous open frame structure was formed. [48][49][50] Particularly, iron-aminoantipyrine (Fe-AAPyr) has been successfully used in double chamber MFC (DCMFC), 14 ceramic based MFC 44 and single chamber MFC. 45 Further advancements have been shown with the investigation of iron-based catalysts 52 In this present work, catalyst formulation and preparation was changed from previously reported studies, and no SSM was applied.…”