Electrochemical cell catalyst layers
An electrochemical cell includes an anode, a cathode, and a membrane physically separating the anode from the cathode, the cathode having a cathode catalyst layer including an ionomer and an electrocatalyst support substrate forming an ionomer-support interface having a covalent bond between the substrate and the ionomer via a grafting compound, the substrate further having a plurality of terminated hydrophilic groups.
1 . An electrochemical cell comprising:
an anode;
a cathode; and
a membrane physically separating the anode from the cathode,
the cathode having a cathode catalyst layer comprising an ionomer and an electrocatalyst support substrate forming an ionomer-support interface having a covalent substrate-acetyl bond formed between the substrate and the ionomer via a grafting compound, the substrate further having a plurality of terminated hydrophilic groups.
2 . The cell of claim 1 , wherein the grafting compound decomposes to yield the covalent bond and includes diazonium, iodonium, carboxylic acid, acyl chloride, or anhydride.
3 . The cell of claim 1 , the interface further comprising a covalent bond between a reactive group of the grafting compound and an ionomer carbon atom adjacent to a hydrophilic group of the ionomer.
4 . The cell of claim 1 , wherein the substrate includes a carbon-based material.
5 . The cell of claim 1 , wherein the ionomer is homogenously dispersed.
6 . The cell of claim 1 , wherein the electrocatalyst support substrate further includes
a pore-free surface region;
a porous surface region having a plurality of pores;
first electrocatalyst particles adhered to the pore-free surface region; and
second electrocatalyst particles housed within the plurality of pores, the second electrocatalyst particles being different from the first electrocatalyst particles.
7 . The cell of claim 6 , wherein the plurality of pores housing the second electrocatalyst are mesopores.
8 . The cell of claim 6 , wherein at least some of the plurality of pores include an external edge and the second electrocatalyst particles are adhered to the external edge.
9 . The cell of claim 6 , wherein the second electrocatalyst is an alloy comprising a noble metal and a transition metal.
10 . The cell of claim 6 , wherein the first electrocatalyst has a different chemical composition than the second electrocatalyst.
11 . An electrochemical cell comprising:
an anode;
a cathode; and
a membrane physically separating the anode from the cathode,
the cathode having a cathode catalyst layer comprising an ionomer and an electrocatalyst support substrate forming an ionomer-support interface having a covalent bond between the substrate and the ionomer via a grafting compound including a benzeneiodonium group, the substrate further having a plurality of terminated hydrophilic groups.
12 . The cell of claim 11 , wherein the covalent bond is formed between a hydrophilic group of the substrate and the benzeneiodonium grafting compound that decomposes to yield a covalently bound aryl group during grafting.
13 . The cell of claim 11 , wherein the substrate includes a carbon-based material.
14 . The cell of claim 11 , wherein the grafting compound is a benzeneiodonium salt.
15 . The cell of claim 11 , wherein the electrocatalyst support substrate further includes a pore-free outer surface region and porous surface region having a plurality of pores, each of the plurality of pores having a cavity defined by a wall;
a first electrocatalyst; and
a second electrocatalyst being different from the first electrocatalyst.
16 . The cell of claim 15 , wherein the first electrocatalyst has a plurality of particles attached to the pore-free outer surface region and the second electrocatalyst has a plurality of particles housed within the cavities of the plurality of pores.
17 . The cathode catalyst layer of claim 15 , wherein at least some of the plurality of pores include an external edge and particles of the second electrocatalyst are adhered to the external edge.
18 . The cathode catalyst layer of claim 15 , wherein the first and second electrocatalysts are located directly adjacent to one another.
19 . An electrochemical cell comprising:
an anode;
a cathode; and
a membrane physically separating the anode from the cathode,
the cathode having a cathode catalyst layer comprising an ionomer and an electrocatalyst support substrate forming an ionomer-support interface having a covalent bond between the substrate and the ionomer via a grafting compound including oxygen atoms of an epoxy group, the substrate further having a plurality of terminated hydrophilic groups.
20 . The cell of claim 19 , wherein the epoxy group is derived from the grafting compound that reacts with a hydrophilic group of the substrate.
21 . The cell of claim 19 , wherein the substrate includes a carbon-based material.
22 . The cell of claim 19 , wherein the ionomer is homogenously dispersed.
23 . The cell of claim 19 , wherein the cathode catalyst layer further comprises a first electrocatalyst and a second electrocatalyst different than the first electrocatalyst, the first electrocatalyst located on a non-porous surface of the electrocatalyst support substrate and the second electrocatalyst located in porous cavities of the electrocatalyst support substrate.
24 . The cell of claim 23 , wherein the porous cavities are mesopores.
25 . The cell of claim 23 , wherein the second electrocatalyst is a platinum-based metal alloy.
26 . The cell of claim 23 , wherein a ratio of the first electrocatalyst:second electrocatalyst is about 1:1.