Robust Superhydrophobic Graphene-Based Composite Coatings
with Self-Cleaning and Corrosion Barrier Properties
Md J. Nine, Martin A. Cole, Lucas Johnson, Diana N. H. Tran, and Dusan Losic*
School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5005, Australia
* S Supporting Information
ABSTRACT: Superhydrophobic surfaces for self-cleaning applications often suffer from mechanical instability and do not
function well after abrasion/scratching. To address this problem, we present a method to prepare graphene-based
superhydrophobic composite coatings with robust mechanical strength, self-cleaning, and barrier properties. A suspension has
been formulated that contains a mixture of reduced graphene oxide (rGO) and diatomaceous earth (DE) modified with
polydimethylsiloxane (PDMS) that can be applied on any surface using common coating methods such as spraying, brush
painting, and dip coating. Inclusion of TiO
2
nanoparticles to the formulation shows further increase in water contact angle
(WCA) from 159 ± 2° to 170 ± 2° due to the structural improvement with hierarchical surface roughness. Mechanical stability
and durability of the coatings has been achieved by using a commercial adhesive to bond the superhydrophobic “paint” to various
substrates. Excellent retention of superhydrophobicity was observed even after sandpaper abrasion and crosscut scratching. A
potentiodynamic polarization study revealed excellent corrosion resistance (96.78%) properties, and an acid was used to provide
further insight into coating barrier properties. The ease of application and remarkable properties of this graphene-based
composite coating show considerable potential for broad application as a self-cleaning and protective layer.
KEYWORDS: graphene, graphene coatings, superhydrophobic surface, self-cleaning, barrier coating, diatomaceous earth
1. INTRODUCTION
Engineered superhydrophobic surfaces (water contact angle
>150°), combining dual-scale roughness and hydrophobic
chemistry, have been studied for self-cleaning applications
since the group at Kao corporation
1
first demonstrated artificial
superhydrophobic surfaces.
1-3
Self-cleaning surfaces allow
water droplets to pick up and remove dust, viruses, and
bacteria during bouncing and rolling contact with the surface.
Superhydrophobic properties are desirable for many industrial
and biological applications including deicing
4
and self-cleaning
of antennas, windows, automobile windshields, and outdoor
textiles,
5
as well as for enhanced antibacterial
6
and antibiofoul-
ing
7
surfaces for medical and marine industries. However, a
common weakness of these surfaces is susceptibility to
mechanical abrasion that eliminates the self-cleaning function
due to destruction of roughness and removal of the layer.
8
Furthermore, existing deposition methods limit the size, shape,
and materials of targeted substrates. These fabrication methods
of superhydrophobic surfaces include template-based extru-
sion,
9
chemical vapor deposition (CVD),
10
electrospinning,
11
extrusion,
12
plasma etching,
13
self-assembly,
14
layer by layer
deposition,
15
sol-gel process,
16
and lithographic methods.
17
Polydimethylsiloxane (PDMS) is one of the most frequently
used surface modifiers to create superhydrophobic surfaces.
Introduction of different surface textures such as porous,
13
hierarchical structure,
14
or microsized replicated pillars
18
on
PDMS with different textured materials creates a suitable
chemistry/topography combination for facile fabrication of
superhydrophobic surfaces. To date, PDMS has been used as a
biomimicking template,
19
embossing platform,
18
precursor of
CVD,
20
and composite matrix
21
and as a hydrophobic modifier
and binding agent of different types of materials, such as
oligomeric silsesquioxane (POSS) nanoparticles,
11
polytetra-
fluoroethylene (PTFE) particles,
13
tetraethyl orthosilicate
(TEOS),
16
candle soot,
20
ZnO,
21
SiO
2
/TiO
2
composite,
22
and CaCO
3
/SiO
2
composite.
23
Many of these methods and
techniques shows very good results in terms of super-
hydrophobicity and self-cleaning properties, but their scal-
ability, robustness, or cost limit their potential for industrial
application. In this regard, durable, cost-effective, easy to apply
superhydrophobic coatings with multifunctional properties are
required in order to realize benefits across many industries
where protective coatings can improve function.
Received: October 9, 2015
Accepted: December 3, 2015
Published: December 3, 2015
Research Article
www.acsami.org
© 2015 American Chemical Society 28482 DOI: 10.1021/acsami.5b09611
ACS Appl. Mater. Interfaces 2015, 7, 28482-28493