Introduction - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 6

performance and high cost of Pt-based electrocatalysts. In addition, efficient
hydrogen storage is also critical for the commercialization of hydrogen-powered
fuel cells. In the chapter by Wei Chen et al., the development of one-dimensional
(1D) palladium (Pd)-based nanomaterials as efficient electrocatalysts for fuel cells is
presented. Among all Pt-free catalysts, Pd has been found to be a promising sub-
stitute owing to its excellent catalytic properties and lower material cost compared
to Pt. Moreover, Pd-based materials exhibit high hydrogen storage capability which
is desirable for hydrogen-powered fuel cells. This chapter reviews the most recent
progress in the synthesis of 1D Pd-based nanomaterials for fuel cell applications.
Areas addressed include controllable synthesis of Pd-based nanostructures through
various synthetic routes, their high catalytic performance for electro-oxidation of
small organic molecules and oxygen reduction reaction (ORR), and the high
capacities for hydrogen storage exhibited in 1D Pd-based nanomaterials.
In another chapter on fuel cells contributed by Kumar and Pillai, the development
of low-cost nanomaterials for high performance polymer electrolyte fuel cells is
reviewed. Proton exchange membrane fuel cells (PEMFCs) utilize a polymer
electrolyte membrane to transport protons from the anode to the cathode and restrict
electrons from directly going to cathode from anode. They have garnered great
interest due to their easy start-up and flexible design. A typical PEMFC consists of
several critical components: Pt electrocatalysts, catalyst support (e.g., carbon), gas
diffusion layer or backing layer, bipolar plate, and polymer electrolyte membrane.
The successful operation of PEMFCs relies on the formation of effective triple phase
boundary (reactant gases, electrocatalysts, and polymer electrolyte membrane) to
facilitate efficient electrochemical reactions at both anode and cathode. However,
the commercialization of PEMFCs is facing obstacles due to the high materials cost
associated with Pt electrocatalysts and the poor performance of existing polymer
electrolyte membranes. This chapter provides the most recent progress on the
development of nanomaterials for PEMFCs in both fundamental and technological
aspects with special emphasis on carbon-based nanostructures such as carbon
nanotubes, graphene, nanostructured Pt electrocatalysts, and bio-inspired catalysts
development, followed by a sound conclusion and perspective on the future activ-
ities in developing low-cost, high performance PEMFCs.

5 Batteries

Electrochemical energy storage (EES) technologies, including flow redox batter-
ies, super capacitors, and rechargeable batteries (Pb-acid, Ni-Cd, Na-S, and Li-
ion batteries, etc.), have demonstrated significant advantages including high effi-
ciency, low-cost, and flexibility. Li-ion batteries in particular are currently con-
sidered as one of the most promising technologies due to their long lifetime and
high energy density. However, for widespread EES applications, there is an
increasing concern about the costs and the limitations of natural lithium reserves.
As

a result, efforts have been made to explore low-cost and reliable EES