апрель 2017

Palladium based anode catalysts supported on conducting polymer/multi-walled carbon nanotubes composites for applications in environmentally-friendly direct formic acid fuel cells

Kupiec K. R. , Borodziński A. , Lin H.-M. , Chiou Y.-J. , Pięta P. , Mikołajczuk-Zychora A. , Kędzierzawski P. , Stobiński L.
Химия и современные технологии
Abstract / Full Text

Sustainable development requires that the energy sector constantly increase efficiency and shift to environmentally friendly energy systems. Clean energy carriers that do not contribute to environmental pollution are crucial. Fuel cell systems offer an effective option for improving sustainability mainly by supporting the use of renewable energy and by increasing efficiency of energy conversion. Fuel cells convert chemical energy directly into electricity through electrochemical reactions. PEM (Proton Exchange Membrane) fuel cells fed with H2 and DMFC (Direct Methanol Fuel Cell) fed with CH3OH have attracted considerable interest. Despite many years of intense research on mentioned above technologies essential drawbacks remain. PEM fuel cells fed with H2 are limited by hydrogen storage and safety issues. The main obstacle for adoption of DMFCs is the toxicity of CH3OH and risk of formation of harmful electrooxidation side products (formaldehyde). Furthermore, DMFCs exhibit significant fuel losses and decrease in fuel cell efficiency due to fuel crossover from anode to cathode via ionomer membranes.

The use of HCOOH as a fuel for fuel cells (DFAFC – Direct Formic Acid Fuel Cell) provides an option free of the obstacles coming from the use of H2 and CH3OH. Formic acid is completely biodegradable and easy to store and to distribute. A DFAFC is much more efficient than DMFCs and PEMs fed with H2.

In our research, palladium based catalysts were used instead of more expensive platinum based ones commonly used in DMFC and PEM. The proposed innovation involves the use of composites of conducting polymers and multi-walled carbon nanotubes (CP/MWCNTs) for supporting nanosized Pd particles in DFAFCs. A common choice for catalyst support material is carbon black. However, it does not exhibit sufficient resistance to corrosion caused by electrochemical oxidation and it is not permeable to gases and liquids. Additionally, carbon black does not conduct protons. These disadvantages limit the performance of the fuel cell. Among all conjugated heterocyclic conducting polymers, polyaniline (PANI) and polypyrrole (PPy) are the ones that our research is particularly focused on. PANI and PPy are permeable to gases and water, and show both electronic and ionic conductivity. The polymerization reactions were performed by both chemical and electrochemical methods. For the purpose of electropolymerization, a system was designed to enable polymer formation with its simultaneous deposition on carbon fabric coated with MWCNTs. Palladium was deposited by various chemical and electrochemical methods. The fuel cell test of palladium catalysts deposited on CP/MWCNTs composites showed promising activity and stability over time when compared to commercially available palladium supported on carbon black.

The potential uses of DFAFCs with our catalyst are in drones, yachts, as well as military and medical exoskeletons.

This work was supported by The National Centre for Research and Development, grant: NCBIR DKO/PL-TW1/1/2013