TY  - JOUR
AU  - Kumar, Rohit
AU  - Mooste, Marek
AU  - Ahmed, Zubair
AU  - Akula, Srinu
AU  - Zekker, Ivar
AU  - Marandi, Margus
AU  - Käärik, Maike
AU  - Leis, Jaan
AU  - Kikas, Arvo
AU  - Treshchalov, Alexey
AU  - Otsus, Markus
AU  - Aruväli, Jaan
AU  - Kisand, Vambola
AU  - Tamm, Aile
AU  - Tammeveski, Kaido
PY  - 2023
TI  - Highly active ZIF-8@CNT composite catalysts as cathode materials for anion exchange membrane fuel cells
JO  - Industrial Chemistry & Materials
SN  - 2755-2608
SP  - 526
EP  - 541
VL  - 1
IS  - 4
AB  - Developing non-precious metal-based inexpensive and highly active electrocatalysts for the oxygen reduction reaction (ORR) in alkaline media is important for fuel cell applications. Herein, we report a simple and effective synthesis of transition-metal-doped zeolitic imidazolate framework-8 (ZIF-8) and carbon nanotube (CNT) composite catalysts (ZIF-8@CNT) prepared via high-temperature pyrolysis at 900 ℃. The catalysts were characterized using different physicochemical techniques and employed as cathode materials in anion exchange membrane fuel cells (AEMFC). The prepared metal-free (ZNT-900), single-metal-doped (Fe-ZNT-900, Co-ZNT-900) and binary-metal-doped (Fe1Co1-ZNT-900, Fe1Co2-ZNT-900) catalysts had a sufficient amount of N-doping with the presence of FeCo moieties in the carbon skeleton of the latter two materials. N2 adsorption–desorption isotherms showed that all the prepared catalysts possess a sufficient Brunauer–Emmett–Teller surface area with more micropores present in ZNT-900, while a combined micro–mesoporous structure was obtained for transition-metal-doped catalysts. Binary-metal-doped catalysts showed the highest number of ORR-active sites (pyridinic-N, pyrrolic-N, graphitic-N, M–Nx) and exhibited a half-wave potential (E1/2) of 0.846 and 0.847 V vs. RHE for Fe1Co1-ZNT-900 and Fe1Co2-ZNT-900, respectively, which surpassed that of the commercial Pt/C catalyst (E1/2 = 0.834 V). In H2–O2 AEMFCs, the Fe1Co2-ZNT-900 catalyst delivered a maximum power density (Pmax) of 0.171 W cm−2 and current density at 0.5 V (j0.5) of 0.326 A cm−2, which is very close to that of the Pt/C catalyst (Pmax = 0.215 W cm−2 and j0.5 = 0.359 A cm−2). The prepared ZIF-8@CNT catalysts showed remarkable electrocatalytic ORR activity in 0.1 M KOH solution and fuel cell performance comparable to that of the benchmark Pt/C catalyst.
UR  - https://doi.org/10.1039/d3im00081h
DO  - 10.1039/d3im00081h