High-Performance Core–Shell Catalyst with Nitride Nanoparticles as a Core: Well-Defined Titanium Copper Nitride Coated with an Atomic Pt Layer for the Oxygen Reduction Reaction

Abstract

A class of core-shell low-platinum catalyst, with well-dispersed inexpensive titanium copper nitride nanoparticles as cores and atomic platinum layers as shells exhibiting high activity and stability for the oxygen reduction reaction (ORR) is successfully developed. Using nitrided carbon nanotubes (NCNTs) as the support greatly improved the morphology and dispersion of the nitride nanoparticles, resulting in significant enhancement of the catalyst's performance. The optimized catalyst, Ti0.9Cu0.1N@Pt/NCNTs, has a Pt mass activity five times higher than that of commercial Pt/C, comparable to that of core-shell catalysts with precious metal nanoparticles as the core and much higher than the latter if we take into account the mass activity of all platinum-group metals. Furthermore, only a minimal loss of activity is observable after 10,000 potential cycles, demonstrating the catalyst's high stability. Atomic-scale elemental mapping confirmed that the core-shell structure of the catalyst remained intact after durability testing. The approach may open a pathway to design and prepare high performance inexpensive core-shell catalysts for a wide range of applications in energy-conversion processes.

Stable and Active Oxygen Reduction Catalysts with Reduced Noble Metal Loadings through Potential Triggered Support Passivation

“…In a previous study, imperfect Pt coverages on a non‐noble core material has led to fast and quantitative dissolution of the core revealing the need for material combinations that can withstand the harsh ORR conditions . Early transition metal carbides were reported to exhibit metallic conductivity, high corrosion resistance and are able to strongly bind to noble metals such as Pt anchoring it in place . Our own research revealed stabilization of tungsten carbide compared to bare tungsten, and we were able to identify the metal‐carbon bond enthalpy as stabilization criterion for various metal carbides .…”

“…While platinum (Pt) is the element with the highest specific activity towards the ORR, its scarcity is its major disadvantage . An interesting, yet not industrially established concept comprises the use of core‐shell structures with a cost‐efficient core material that supports a noble metal film with a thickness lying in the monolayer (ML) range . The main advantages of such a design over monometallic catalysts are enhanced SA, a drastic decrease in noble metal loading and significant cost benefits .…”

Core–Shell-Structured Low-Platinum Electrocatalysts for Fuel Cell Applications

“…And after 10,000 potential cycles, the TiN@Pt and TiNiN@Pt catalysts only degraded by a negative shift of 17 and 10 mV in its half-wave potential, respectively, whereas Pt/C showed a degradation of more than 25 mV (E 1/2 ), demonstrating the long-term stability of the resulting TiNiN@Pt catalyst. Other bimetallic nitride cores covered by Pt shells, such as PdNiN, TiWN, and TiCuN, have also been reported to display enhanced catalytic activities and stabilities for ORR [547][548][549] and these developments open up broad feasibilities for the design and synthesis of various TMN nanoparticle-based core-shell structures for applications in electrocatalysis. However, many problems still exist for TMN core applications.…”

Noble Metal-Based Nanocomposites for Fuel Cells

“…Adzic and co-workers have fabricated various core-shell electrocatalysts with monolayer and ultrathin Pt shell via Cu under potential deposition (UPD) and pulse electrodeposition (PED). The core materials contain intermetallics (PtPb, PdPb, PdFe) [70], core-shell (Pd@PdAu) [71], alloy (AuNi) [72] and transition metal nitride (TiCuN) [73]. As shown in Figure 3, in an UPD process, they prepared core first, then dropped onto a flat glassy electrode to form a thin film.…”