PTL titanium is a porous transport layer, which is located between the bipolar plate and the anode catalyst layer. It plays the role of water transport (reaction water inflow), exhaust (oxygen bubble discharge), heat conduction (heat output), and electrical conduction in the anode oxygen evolution reaction.
The anode porous transport layer has gone through the titanium mesh → titanium particle sintered plate → titanium fiber sintered felt (referred to as titanium felt) and other structures. Titanium felt is currently a common choice for porous transport layers at home and abroad because of its simple manufacturing process and high porosity.
The anode porous transport layer is an integration of the four-phase field of gas, liquid, electricity, and heat.
① PTL is the intersection of gas and liquid. The reaction water comes in through PTL, and the generated oxygen bubbles go out through PTL. It is necessary to make the two-way flow of water and gas smoother and reduce convection resistance as much as possible; the traditional titanium felt structure is disordered, and its internal pore structure is randomly distributed, resulting in a large transmission resistance of reaction water and oxygen bubbles inside it.
②PTL needs to assume the function of conducting electricity, and needs to increase the contact surface with the catalyst layer as much as possible; the contact between titanium felt and the catalyst layer is line contact, and the contact surface is small, resulting in fewer electrochemical reaction sites at the junction of gas, liquid and solid phases, and higher impedance.
③The structure of PTL will affect the membrane electrode in contact with it; the pore sizes on the surface of titanium felt vary, with a large standard deviation, and the largest pore size may even exceed 100 microns. Under the pressure difference between the anode and cathode (3.5MPa), the membrane electrode is easily "squeezed" into the pores, resulting in "bulging" of the membrane electrode; at the same time, the larger pore size is more prone to reaction and more loss, and the "short board effect" will shorten the overall life of the membrane electrode.
In view of the shortcomings of the titanium felt structure, the industry has developed a new straight-through pore structure porous transport layer (SP-PTL, Straight Pore-PTL for short).
From the first principle, the straight-through pore structure porous transport layer
① The pores are straight up and down, and the water inlet and oxygen outlet are smoother, and the advantages are more obvious under high current density;
② It is in surface contact with the catalyst layer, which greatly reduces the contact surface resistance;
③ The pore size is smaller than the thickness of the mainstream PEM membrane, and the pore size is uniform and the standard deviation is small, which is not easy to cause membrane electrode bulging and uneven reaction problems. For a 1MW PEM electrolyzer, the cost of unplatinized titanium felt is 230,000 yuan, and the cost of unplatinized straight-through pore structure is only 90,000 yuan, a 60% reduction in cost.
In addition, the structural characteristics of titanium felt determine that its most suitable coating method is water electroplating, and it is not suitable for PVD physical vapor deposition, which saves more precious metals. The internal conduction of the titanium felt structure is through the sintering points of the titanium wires. In the environment of strong anodic oxidation and strong acid, it is usually necessary to immerse all the sintering points of the titanium wires inside the titanium felt in the electroplating solution and plate them with a platinum protective layer to ensure the service life.
Our company has many years of experience in producing PTL titanium felt. Welcome to consult us.
Nicole
Company: Baoji Jimiyun Dynamic Co., Ltd
Country:China
Add:Baoti road,Jintai,Baoji city,Shaanxi,China
Cel:+86 13369210920
Gmail:nicole@jmyunti.com
Website:www.jm-titanium.com
