<p>Composites synthesized through the deposition of Mn<sub>3</sub>O<sub>4</sub>
on graphene, carbon nanotube and other carbon based materials have attracted
much attention recently as potential electrode materials for different
electrochemical applications such as pseudocapacitor; Lithium-ion battery; and catalysis. The primary reason Mn<sub>3</sub>O<sub>4</sub>
is grown on these substrates in spite of having high charge storage capacity as pseudocapacitor or Lithium-ion battery electrodes on its own is to enhance its electrical conductivity and/or to impart flexibility to the electrode, which is
difficult for a fully metallic electrode. Higher electrical conductivity
prolongs the cycle life of an electrode. In addition, the substrate contributes
capacity and thus, enhances the overall energy density of an electrode. Mn<sub>3</sub>O<sub>4
</sub>acts as a spacer and keeps graphene nanosheets separated when used as the
substrate for capacitor electrode fabrication. This helps retain the high
surface area of graphene nanosheets in the electrode which contributes
additional capacitance. Mn<sub>3</sub>O<sub>4 </sub>supported on graphene and
other carbon substrates have recently been investigated as catalyst for
methanol electro-oxidation in alkaline media; CO oxidation; and
Oxygen reduction reaction (ORR). High surface area substrate uniformly
distributes metal particles and prevents their agglomeration and dissolution
during catalytic process. In addition, high electrical conductivity of graphene
and carbon substrates enhances the electronic conductivity of Mn<sub>3</sub>O<sub>4</sub>
which is of importance for superior catalytic activity. Composite of Mn<sub>3</sub>O<sub>4</sub>
combined with carbon based substrate has also found non-electrochemical
application such as the removal of Pb and Cu ions from aqueous solution because
of their adsorptive behaviour.<b></b></p>
<p>A myriad of procedures have been adopted for the synthesis
of Mn<sub>3</sub>O<sub>4</sub> on graphene or other carbonaceous substrates. All of these methods
involve one or more of the following factors that complicate the process, such
as: long synthesis time; high synthesis temperature; use of hazardous/toxic
chemicals; multistep process and the requirement for sophisticated device or
highly controlled environment. In fact, the complicacies associated with the
synthesis of Mn<sub>3</sub>O<sub>4</sub> have already been acknowledged and
investigations have been directed at finding relatively simpler route such as
the use of microwave technique. <b></b></p>
<p>In this research, we report the synthesis of clusters of
nearly octahedral shapedn Mn<sub>3</sub>O<sub>4</sub> nanoparticles on few-layer
graphene nanoplatalet (GnP) surface through a simple, wet-chemical,
polyethyleneimine (PEI) mediated route. Few-layer graphene nanoplatelets are
ultrathin particles of graphite prepared through proprietary intercalation and
exfoliation method (XG Sciences, Inc., Lansing, MI, USA). The components
involved in this synthesis method are manganese salts (KMnO<sub>4</sub> and MnSO<sub>4</sub>.H<sub>2</sub>O); water; PEI; and GnP as the substrate. The
synthesis is carried out at a temperature of 80°C only and in open air. Highly
crystallized Mn<sub>3</sub>O<sub>4</sub> particles, as observed by X-Ray
Diffraction (XRD), can be synthesized on GnP surface. It has also been observed
that PEI acts as a reducing agent and as a capping agent on a continuous
network of ribbon-like Birnessite-MnO<sub>2</sub> (IV) to produce a nearly
octahedral shaped nanoparticles of Mn<sub>3</sub>O<sub>4</sub> (II, III). It
has already been mentioned that composites of Mn<sub>3</sub>O<sub>4</sub> on
graphene or other carbonaceous substrates find a myriad of applications. Thus,
our research findings to synthesize GnP-Mn<sub>3</sub>O<sub>4</sub> composite
through a simple method should be of interest to a broad group of researchers.
In this research, we have investigated the performance of this composite system
as a Lithium-ion battery anode only. Our preliminary investigations reveal that
the Mn<sub>3</sub>O<sub>4</sub> composite synthesized through this method has
just as much potential as the ones prepared through other alternative methods.</p>
Green Synthesis of Clean Edge Graphene Nanosheets Using Natural Precursor
