Correlation between the TiO 2 encapsulation layer on Pt and its electrochemical behavior

Zhang

et al. 2022

J. Phys. Chem. Lett.

Stability and antipoisoning effects are the main challenges for the application of commercial Pt/C catalysts. Herein, we soaked and adsorbed polydopamine to coat Pt particles on commercial Pt/C and subsequently converted the coatings to few-layer N-doped graphene by calcination to produce Pt/C@NC. The coatings effectively block the direct contact of Pt nanoparticles and electrolyte, thus enhancing the catalyst stability by avoiding Ostwald ripening and suppressing the competitive adsorption of toxicants, contributing to the enhancement of the antipoisoning ability. More importantly, the coatings do not hurt the oxygen reduction reaction (ORR) activity of commercial Pt/C, which exhibits a half wave potential of 0.84 V in an acidic electrolyte. The spectroscopic and theoretical results confirmed that the coatings originate from a strong Pt bonding to pyridinic N of N-doped graphene and that the high ORR activity results from the coordinately unsaturated carbon atoms, as the real ORR active sites, to strongly capture electrons from Pt.

mentioning

confidence: 99%

N-Doped Graphene-Coated Commercial Pt/C Catalysts toward High-Stability and Antipoisoning in Oxygen Reduction Reaction

Zhang

et al. 2022

J. Phys. Chem. Lett.

“…Another steric protection strategy lies in encapsulating the active catalyst using a thin conductive (oxide) layer. Specifically, TiO 2 has been targeted and demonstrated to be effective in protecting platinum particles from agglomeration. , Increasing the metal–support interaction and the use of confinement strategies lead to a decrease in particle agglomeration.…”

Section: What Are the Dominant Degradation Pathways In Aqueous Electr...mentioning

confidence: 99%

“…Specifically, TiO 2 has been targeted and demonstrated to be effective in protecting platinum particles from agglomeration. 141,142 Increasing the metal− support interaction and the use of confinement strategies lead to a decrease in particle agglomeration.…”

Section: What Are the Dominant Degradation Pathways In Aqueous Electr...mentioning

confidence: 99%

Catalyst Stability in Aqueous Electrochemistry

2022

Self Cite

The main challenges in catalysis are high activity, selectivity, cost efficiency, and stability. In industrial processes, stability in particular is of pressing concern, and its importance has become more and more acknowledged in academia. At the same time, the need for alternatives to replace fossil raw materials is omnipresent, and the electrification of synthetic processes is picking up in speed. New processes are being developed and novel materials are being tested, while assessing the stability of emerging catalysts can be time-consuming and frustrating but, at the same time, highly important. This problem is exacerbated by a clear lack of realistic stability measurements of new catalysts and an understanding of the key driving forces for the specific degradation pathway. In this perspective, deactivation processes in aqueous electrochemistry are selectively discussed and mitigation strategies are presented. A special focus is placed on the intrinsic material properties that react to the surrounding environment. The applied conditions not only predefine the product spectrum and activity of the catalytic material but also strongly influence the catalyst’s stability. We review various concepts to increase the stability, for instance, by tailoring the coordination environment around the active center, and highlight the importance of the support material. The presented concepts together with stability descriptors serve as important guidelines toward stable and sustainable catalyst systems.

“…Its hydrogen adsorption peak was larger than the hydrogen desorption peak, which is known as a hydrogen spillover from Pt to the TiO 2 support. [58][59][60] Hydrogen spillover effect can occur when the TiO 2 support possesses rich and deficient oxygen vacancies 59 and Pt nanoparticles are covered with TiO 2 . 60 In the present experiments, Pt was deposited by coaxial APD to form Pt/Nb-Ti 4 O 7 in which the generated Pt ions are accelerated by a strong magnetic field induced in the coaxial arc plasma gun and are ejected toward the target substrate under vacuum.…”

Section: Physical Characterization Of Pt/nb-ti 4 O 7 Catalystsmentioning

confidence: 99%

“…[58][59][60] Hydrogen spillover effect can occur when the TiO 2 support possesses rich and deficient oxygen vacancies 59 and Pt nanoparticles are covered with TiO 2 . 60 In the present experiments, Pt was deposited by coaxial APD to form Pt/Nb-Ti 4 O 7 in which the generated Pt ions are accelerated by a strong magnetic field induced in the coaxial arc plasma gun and are ejected toward the target substrate under vacuum. Miyazaki et al employed STEM-electron energy loss spectroscopy analysis and determined that a GC substrate irradiated by Pt ions was damaged to depths of approximately 15-17 nm from the substrate surface.…”

Section: Physical Characterization Of Pt/nb-ti 4 O 7 Catalystsmentioning

confidence: 99%

Degradation Analysis of Pt/Nb–Ti4O7 as PEFC Cathode Catalysts with Controlled Arc Plasma-deposited Platinum Content

KAJIMA

Shimasaki

et al. 2022

Electrochemistry

For polymer electrolyte fuel cell cathodes, highly durable supports are required to prevent catalyst degradation in supports. In this study, as model Pt catalysts, 2-10 wt% Pt was deposited on Magnéli-phase niobium-doped macroporous Ti 4 O 7 (Nb-Ti 4 O 7 ) mounted on glassy carbon rods using the coaxial arc plasma deposition method. The morphologies of 2, 5, and 10 wt% Pt catalysts showed the hemisphere fine particles, islands with ca. 1.4 nm diameter and ca. 2.4 nm thickness, and films with ca. 3.3 nm thickness, respectively. During start/stop accelerated durability tests (ADTs) of 5000 cycles following the Fuel Cell Commercialization Conference of Japan protocol, Pt was slightly agglomerated; consequently, the morphologies of the 2, 5, and 10 wt% Pt catalysts were island-like with 3.5 nm thickness, chain bead-like with 4 nm thickness, and film-like with 4 nm thickness, respectively. This slight agglomeration led to good durability during the ADTs. Herein, the oxygen reduction reaction (ORR) mass activity (MA) values at 0.9 V vs. reversible hydrogen electrode (RHE) of the 2, 5, and 10 wt% Pt catalysts were 79, 60, and 36 A g À1 Pt after 5000 cycles ADT, respectively, which had declining ratios after 5000 cycles were 32 %, 17 %, and 0 %, respectively. The island-like and film-like Pt/Nb-Ti 4 O 7 presented activity and durability comparable to a Pt/C catalyst, which was 42 A g À1 Pt (0.9 V vs. RHE) with a 12 % of declining ratio after the ADTs. The durability of the MA suggested that the different affinity caused by different crystal faces led to the slight agglomeration of 2, 5, and 10 wt%_Pt/Nb-Ti 4 O 7 catalysts. These catalysts showed electrochemical surface areas (ECSAs) of 36, 27, and 29 m 2 g −1 after the ADTs, with declining ratios as low as 20 %, 6 %, and 0 %, respectively. All Pt/Nb-Ti 4 O 7 catalysts showed higher durability of the ECSAs than the Pt/C catalyst, which was 68 m 2 g −1 with a 30 % declining ratio after the ADT. Different from common Pt nanoparticle catalysts, which agglomerate into large spherical Pt particles, the slight agglomeration was caused by the interconnection of the deposits and supplemented by a limited increase in the diameter or thickness. The island-like morphology of Pt with a limited thickness presented both high durability and activity among the Pt/Oxide catalysts.