Electronic Effects of Nitrogen Atoms of Supports on Pt–Ni Rhombic Dodecahedral Nanoframes for Oxygen Reduction

Abstract

Pt-based nanostructures immobilized on carbon supports have been widely used as electrocatalysts. Their catalytic activity can be improved by support modification including nitrogen doping and coating with nitrogen-containing polymers, where nitrogen atoms possibly interact with surface Pt atoms at a catalyst/support interface. To understand electronic effects of nitrogen-doped and polymer-coated carbon supports on the catalytic activity of Pt-based nanostructured catalysts, we prepared Pt 3 Ni nanoframes (NFs) supported on polybenzimidazole (PBI)-coated and uncoated carbon nanotubes for the oxygen reduction reaction (ORR), and then compared their catalytic activities and electronic properties with those of NFs immobilized on nitrogen-doped and undoped carbon supports. Although both PBI-coating and nitrogen-doping approaches improved the catalytic activity of NFs, ex situ X-ray photoelectron spectroscopy and in situ X-ray absorption spectroscopy revealed that nitrogen doping showed electronic effects on NFs, whereas PBI-coating showed almost no impact on the electronic state of NFs but stabilized Pt(OH) ad species under electrochemical conditions. Our studies demonstrate that difference in microscopic environments of nitrogen atoms at the catalyst/ support interface is highly sensitive to the electronic effects of supports on Pt-based electrocatalysts.

Impact of Heterometallic Cooperativity of Iron and Copper Active Sites on Electrocatalytic Oxygen Reduction Kinetics

“…Interestingly, the comparison between LSVs of (Cu,Fe)–N–CNT and Pt/C undergoing the negative sweep revealed that these E 1/2 values for the ORR were the almost same (Figure S7). Generally, E 1/2 values of LSVs for PGM-based ORR electrocatalysts including Pt/C highly depend on the potential sweep direction, and their LSVs undergoing the negative sweep tend to show more negative E 1/2 than those undergoing the positive sweep since the surface of PGM catalysts can be covered with metal oxide or hydroxide species (M–O­(H)) under oxidative conditions. , This is the reason why representative LSVs of Pt/C are usually shown in the positive-going sweep (Figure ). However, in practice, ORR catalysts with higher catalytic activity undergoing the negative-going sweep should be developed because PEFCs should provide the peak power for fuel cell vehicles during acceleration.…”

Catalyst overcoating engineering towards high-performance electrocatalysis

“…155,164,165 In addition to oxidative polymerization, an easy-handling process involving a simple mixing of the carbon support with an organic entity containing solution followed by a thorough rinsing step has been applied for overcoating with PyPBI, PBI and PVP. 78,[159][160][161][162][166][167][168] Moreover, by utilizing the amide reaction between the -COOH groups of carbon black and the -NH 2 groups of amine-terminated poly(N-isopropylacrylamide) (PNIPAM), Jung et al 169 demonstrated the covalent functionalization of the carbon support with polymers for efficient anchoring of metal species. Of note, since the polymer overlayer can strongly interact with the surface of carbon materials, the subsequent metal deposition and coordinating interactions with functional groups (such as N-containing groups) will be feasible.…”

“…As a result, PtCo/C-PNIPAM displayed higher ORR activity and degradation resistance, in comparison with PtCo/C without PNIPAM functionalization. However, it was recently demonstrated by Kato et al 167 that the PBI overlayer on the carbon support could not impose an effect on the electronic structure of PtNi nanoframes immobilized but, instead, tended to stabilize Pt-(OH) ad species under the ORR conditions for activity improvement. Indeed, they found the electronic effect from the corresponding N-doped carbon-supported PtNi catalyst.…”

Ultrafine platinum nanoparticles supported on N,S-codoped porous carbon nanofibers as efficient multifunctional materials for noticeable oxygen reduction reaction and water splitting performance

“…[40][41][42] The surface of carbon materials evenly and strongly attached to polybenzimidazole through p-p interactions, indicating that the high-dispersibility Pt NPs were immobilized by nitrogen atoms to achieve better catalytic performance for ORR. [43][44][45] Pt NPs have also been prepared by NaBH 4 and ethylene glycol methods. Pt NPs in Pt/MnO 2 -carbon nanobers were prepared using NaBH 4 , and the resultant catalysts exhibit excellent electrochemical properties.…”