%0 Journal Article
%T Evaluation of CoBlast Coated Titanium Alloy as Proton Exchange Membrane Fuel Cell Bipolar Plates
%A Atinuke M. Oladoye
%A James G. Carton
%A Abdul G. Olabi
%J Journal of Materials
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/914817
%X We investigated the potential of graphite based coatings deposited on titanium V alloy by a low-cost powder based process for bipolar plate application. The coatings which were deposited from a mixture of graphite and alumina powders at ambient temperature, pressure of 90£¿psi, and speed of 20£¿mm were characterised and electrochemically polarised in 0.5£¿M H2SO4 + 2£¿ppm£¿HF bubbled with air and hydrogen gas to depict the cathode and anode PEM fuel cell environment, respectively. Surface conductivity and water contact angles were also evaluated. Corrosion current in the 1£¿¦ÌA/cm2 range in both cathodic and anodic environment at room temperature and showed negligible influence on the electrochemical behaviour of the bare alloy. Similar performance, which was attributed to the discontinuities in the coatings, was also observed when polarised at 0.6£¿V and £¿0.1£¿V with air and hydrogen bubbling at 70¡ãC respectively. At 140£¿N/cm2, the coated alloy exhibited contact resistance of 45.70£¿m¦¸¡¤cm2 which was lower than that of the bare alloy (66.50£¿m¦¸¡¤cm2) but twice that of graphite (21.29£¿m¦¸¡¤cm2). Similarly, the wettability test indicated that the coated layer exhibited higher contact angle of 99.63¡ã than that of the bare alloy (66.32¡ã). Over all, these results indicated need for improvement in the coating process to achieve a continuous layer. 1. Introduction Proton exchange membrane (PEM) fuel cells as shown in Figure 1 are energy conversion devices that generate clean electrical energy from the electrochemical reaction between hydrogen and oxygen via an electrocatalyst and a solid polymer membrane at temperatures between 60¡ãC and 80¡ãC. They are increasingly being targeted for transportation and stationary and portable power generation due to their low operating temperature, high power density, quick start-up capacity, and rapid response to varying load advantages over other types of fuel cells [1¨C4]. Nonetheless, the widespread utilisation of these clean power sources for such applications is limited by a number of challenges including cost and durability of PEM fuel cell stack components. Figure 1: Schematic of a single cell PEM fuel cell. A PEM fuel cell stack is made up of several single cells connected in series. Each single cell consists of a thin layered membrane electrode assembly (MEA) sandwiched between two bipolar plates as depicted in Figure 1. The MEA, which is composed of the gas diffusion layer (GDL), the catalyst layer, and the proton exchange membrane (PEM), performs critical roles that control the transport of protons, electrons, and reactant gases
%U http://www.hindawi.com/journals/jma/2014/914817/