Apparatus comprising manganese-cobalt spinel oxide/carbon catalyst
Provided is an apparatus containing, as a cathode catalyst, a metal oxide/carbon catalyst composition. The metal oxide/carbon catalyst composition includes 40 to 95 wt % porous Mn—Co spinel oxide nanoparticles of the formula Mn x Co 3-x O 4 . The nanoparticles have an octahedral morphology, an average particle size of 5-100 nm, and average pore sizes of 1-5 nm (where x is the atomic fraction of manganese and 3-x is the atomic fraction of cobalt). The metal oxide nanoparticles are supported on a carbon substrate that contains at least 96 atomic % carbon.
1. An apparatus comprising an anode, a cathode, and a charge-passing material between the anode and the cathode, the apparatus being an anion-exchange membrane fuel cell (AEMFC) or a membrane electrode assembly (MEA), wherein the cathode comprises a metal oxide/carbon catalyst composition comprising:
40 to 95 wt % metal oxide, said metal oxide being porous Mn—Co spinel oxide nanoparticles of the formula Mn x Co 3-x O 4 , said nanoparticles having an octahedral morphology, an average particle size of 5-100 nm, and average pore sizes of 1-5 nm, and wherein x is the atomic fraction of manganese (Mn), 3-x is the atomic fraction of cobalt (Co), and 0<x<3; and
a carbon substrate comprising at least 96 atomic % carbon,
wherein the metal oxide nanoparticles are supported on the carbon substrate, and wherein said apparatus exhibits a peak power density of at least 0.8 W/cm 2 at a current density of 2.0 A/cm 2 .
2. The apparatus according to claim 1 , wherein the metal oxide/carbon catalyst composition comprises 40 to 90 wt % of the metal oxide nanoparticles.
3. The apparatus according to claim 1 , wherein the metal oxide/carbon catalyst composition comprises 50 to 85 wt % of the metal oxide nanoparticles.
4. The apparatus according to claim 1 , wherein the metal oxide/carbon catalyst composition comprises 60 to 80 wt % of the metal oxide nanoparticles.
5. The apparatus according to claim 1 , wherein the metal oxide is present as a single phase.
6. The apparatus according to claim 1 , wherein the metal oxide is selected from MnCo 2 O 4 , CoMn 2 O 4 , and Mn 1.5 Co 1.5 O 4 .
7. The apparatus according to claim 6 , wherein the metal oxide is MnCo 2 O 4 .
8. The apparatus according to claim 7 , wherein the MnCo 2 O 4 has a single-phase cubic spinel structure.
9. The apparatus according to claim 6 , wherein the metal oxide is CoMn 2 O 4 .
10. The apparatus according to claim 9 , wherein the CoMn 2 O 4 has a single-phase tetragonal spinel structure.
11. The apparatus according to claim 1 , wherein the carbon substrate is not doped.
12. The apparatus according to claim 1 , wherein the carbon substrate is selected from graphite, amorphous carbon, hard carbon, soft carbon, acetylene black, mesocarbon microbeads (MCMB), carbon black, mesoporous carbon, porous carbon matrix, carbon nanotubes, carbon nanofibers, and graphene.
13. The apparatus according to claim 1 , wherein the nanoparticles have an average particle size of 10 to 100 nm.
14. The apparatus according to claim 1 , wherein the apparatus is an AEMFC.
15. The apparatus according to claim 1 , wherein the apparatus is an MEA.
16. The apparatus according to claim 1 , wherein the cathode has a metal oxide loading of at least 0.6 mg metal oxide /cm 2 .
17. The apparatus according to claim 16 , wherein, when operating at 80° C. with 0.1 MPa back-pressure, the apparatus exhibits a peak power density of at least 1.0 W/cm 2 at a current density of 2.0 A/cm 2 .
18. The apparatus according to claim 17 , wherein the apparatus is an MEA, and wherein the MEA comprises a platinum-based (e.g., PtRu/C and Pt/C) anode and an alkaline polymer membrane.
19. The apparatus according to claim 1 , wherein said metal oxide/carbon catalyst composition is present in a catalyst layer having a thickness of 5 to 40 μm.
20. An electrocatalytic process comprising providing or operating an apparatus according to claim 1 , wherein said process comprises use of the metal oxide/carbon catalyst in the cathode to perform an oxygen reduction reaction (ORR).