Rh(Ⅲ)-catalyzed, chelation-assisted oxidative C-H imidation of arenes with N-H imide have been realized using PhI(OAc)2 as an oxidant. This transformation exhibits a broad substrate scope and tolerates various functi...Rh(Ⅲ)-catalyzed, chelation-assisted oxidative C-H imidation of arenes with N-H imide have been realized using PhI(OAc)2 as an oxidant. This transformation exhibits a broad substrate scope and tolerates various functional groups. The reaction proceeded via in situ generation of an iodine(Ⅲ) imido. DFT calculations suggest that this oxidative imidaton system proceeds via a Rh(Ⅲ)-Rh(Ⅴ)-Rh(Ⅲ) pathway.展开更多
The high cost of platinum(Pt)-group metal(PGM)-based catalysts used in proton-exchange membrane fuel cells(PEMFCs)poses a critical roadblock to their widespread adoption.Although using low PGM loading PEMFCs can large...The high cost of platinum(Pt)-group metal(PGM)-based catalysts used in proton-exchange membrane fuel cells(PEMFCs)poses a critical roadblock to their widespread adoption.Although using low PGM loading PEMFCs can largely address this challenge,high current density performance will be severely compromised consequently.To overcome this dilemma,we report the development of ultrathin platinum-cobalt nanowires(PtCoNWs)as the cathode catalysts for ultralow Pt loading and high-performance membrane electrode assembly(MEA).The Pt Co NWs delivered a record-high mass activity(MA)of 1.06±0.14 A mg_(Pt)^(-1) of Pt-alloy catalysts towards oxygen reduction reaction(ORR)in MEA,yielding an impressive total Pt utilization of 5.14 W_(rate)mg_(Pt)^(-1).The PtCoNWs retained a respectable endof-life MA of 0.45 Amg_(Pt)^(-1) after the 30,000 cycles square-wave accelerated stability test,which is still above the Department of Energy 2020 beginning-of-life target for catalysts.In-situ Xray absorption spectroscopy studies suggest that the high degree of alloying in the Pt Co NWs stabilizes the ultrathin structure and may contribute to the high ORR activity and power density performance in PEMFC.展开更多
文摘Rh(Ⅲ)-catalyzed, chelation-assisted oxidative C-H imidation of arenes with N-H imide have been realized using PhI(OAc)2 as an oxidant. This transformation exhibits a broad substrate scope and tolerates various functional groups. The reaction proceeded via in situ generation of an iodine(Ⅲ) imido. DFT calculations suggest that this oxidative imidaton system proceeds via a Rh(Ⅲ)-Rh(Ⅴ)-Rh(Ⅲ) pathway.
基金support from the Office of Naval Research(N000141812155)support from the National Science Foundation(DMREF 1437263)supported in part by the National Science Foundation through the UC Irvine Materials Research Science and Engineering Center(DMR-2011967)。
文摘The high cost of platinum(Pt)-group metal(PGM)-based catalysts used in proton-exchange membrane fuel cells(PEMFCs)poses a critical roadblock to their widespread adoption.Although using low PGM loading PEMFCs can largely address this challenge,high current density performance will be severely compromised consequently.To overcome this dilemma,we report the development of ultrathin platinum-cobalt nanowires(PtCoNWs)as the cathode catalysts for ultralow Pt loading and high-performance membrane electrode assembly(MEA).The Pt Co NWs delivered a record-high mass activity(MA)of 1.06±0.14 A mg_(Pt)^(-1) of Pt-alloy catalysts towards oxygen reduction reaction(ORR)in MEA,yielding an impressive total Pt utilization of 5.14 W_(rate)mg_(Pt)^(-1).The PtCoNWs retained a respectable endof-life MA of 0.45 Amg_(Pt)^(-1) after the 30,000 cycles square-wave accelerated stability test,which is still above the Department of Energy 2020 beginning-of-life target for catalysts.In-situ Xray absorption spectroscopy studies suggest that the high degree of alloying in the Pt Co NWs stabilizes the ultrathin structure and may contribute to the high ORR activity and power density performance in PEMFC.
