Low-Cost Nanomaterials for High-Performance Polymer Electrolyte Fuel Cells (PEMFCs) - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 354

graphite bipolar plate and perfluorosulphonic acid (PFSA) membranes makes the
system very expensive, preventing its commercial applications. For example, the
state-of-the-art PEMFC stacks use a Pt loading of 0.3 mg cm -2 which is too
expensive for commercialization while US Department of Energy (DOE) target for
2015 lie at 0.03 mg cm -2 [ 24 , 25 ]. Further, the use of PFSA membranes limits
the operating temperature below 100 C that necessitates the use of ultrapure
hydrogen as the fuel which further increases the system cost. The net cost of a
transportation fuel cell system (2010 technology) for high volume manufacturing
(500,000 units per year) is $51/kW (Fig. 1 ). This is a reduction of more than 80 %
since 2002 and approaches the target of $30/kW established for 2015. Research
and development efforts appear to be on track to achieve cost-competitiveness with
ICEs within the next few years.
Further, the PFSA-based PEMs have many drawbacks such as dependence on
humidity for conductivity, high reactant permeability, tendency to disintegrate in
the presence of hydroxyl radicals (an intermediate in the cathode reaction) and
moderate mechanical, chemical stability. The use of carbon as the catalyst support
and Pt as the electrocatalyst induce durability-related issues since Vulcan XC-72
carbon materials are reported to corrode after 150 h of continuous operation [ 27 ].
Similarly, other components that are used in fuel cells such as bipolar plates also
have many restrictions related to fragility and affordability and therefore to realize
a commercially feasible fuel cell many of these barriers should be surmounted
using inexpensive options.
5 Nanoscale PEMFC Materials and Their Significant
Properties
We will now describe recent developments in both fundamental and technological
aspects of PEMFCs with a special emphasis on individual nanoscale materials as
well as their assembling process into a single cell and subsequently stack fabri-
cation. This is mainly due to the fact that recent synthesis of a gamut of
nanomaterials with their unique properties have made a tremendous impact on
many thrust areas like energy, electronics, biology and health care [ 28 , 29 ]. For
instance, few non-noble nanomaterials have been claimed to replace expensive
electrocatalysts like Pt and Ru with similar electrocatalytic activity and nano-
composite polymer electrolytes offer several intrinsic advantages like increased
thermal and chemical stability, enhanced mechanical strength and improved ion
transport [ 30 - 32 ]. The section on individual nanoscale components particularly
focuses on novel carbon supports and functionalized surfaces, electrocatalysts of
Pt and non-Pt metals, composite polymer electrolyte membranes with tailor-made
properties, bio-inspired electrocatalysts and composite bipolar plates. This section
also deals with the development of both components and engineering process as
well.