Local Structural Disorder Enhances the Oxygen Reduction Reaction Activity of Carbon-Supported Low Pt Loading CoPt Nanocatalysts

ACS Appl. Energy Mater.

Huang

Chang

et al. 2020

Self Cite

Hydrogen evolution reaction (HER) plays a key role in combating an ever-growing imbalance and adverse climatic issues. Thus far, Pt-based catalysts are treated as "the Holy Grail" for HER and none have surpassed them. However, as the reaction sites are present only on the catalyst surface, Pt utilization is severely hampered. Scaling down the catalyst nanoparticles is a vital approach to maximize the Pt utilization. To address this issue, we fabricated Pt x Pd y (x/y = 1/2, 1/1, and 2/1) bimetallic nanocatalysts (NCs) downsized up to ∼1.2 nm with ultralow metal loading (∼1−3 wt %) and remarkable catalytic performance via a deposition−precipitation method on a carbon support. In the optimum case, the NC with a x/y ratio of 1/1 (i.e., Pt 1 Pd 1 ) exhibits an outstanding mass activity (MA) of 9.57 A mg Pt −1 at 0.05 V versus normal hydrogen electrode in acidic medium (0.5 M H 2 SO 4 ) in HER. This result is 7.4-times enhanced compared to that of the Pt/C NC. Moreover, the Pt 1 Pd 1 NC retains 81% of its MA (7.74 A mg Pt −1 ) when operated in the chronoamperometric stability test (while 39% decay in MA is observed for the Pt/ C NC) up to 12 h. By screening the results of electron microscopy, X-ray spectroscopy, and electrochemical analysis, we revealed that such a substantial improvement is resulted from the decoration of the Pt trimer with high surface coverage and local structure ordering in the Pd crystal. Results of Pt x Pd y with different atomic Pt sizes are compared as a reference for rationalizing the development of ultralow-noble metal loading PtPd NCs in HER.

Section: Resultsmentioning

confidence: 80%

High-Performance and Stable Hydrogen Evolution Reaction Achieved by Pt Trimer Decoration on Ultralow-Metal Loading Bimetallic PtPd Nanocatalysts

ACS Appl. Energy Mater.

Huang

Chang

et al. 2020

Self Cite

“…The electron gun is a LaB6 model and is operated at an accelerating voltage of 200 kV. Details of sample preparation and analysis were reported in a previous study 49 . The crystal structure of the NCs were determined by using X-ray diffraction (XRD) analysis.…”

Section: Physical Characterizationmentioning

confidence: 99%

CO-Reductive and O2-Oxidative Annealing Assisted Surface Restructure and Corresponding Formic Acid Oxidation Performance of PdPt and PdRuPt Nanocatalysts

Huang

Chou

et al. 2020

Sci Rep

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Formic acid oxidation reaction (FAOR) at anode counterpart incurs at substantial high overpotential, limiting the power output efficiency of direct formic acid fuel cells (DFAFCs). Despite intense research, the lack of high-performance nanocatalysts (NCs) for FAOR remains a challenge in realizing DFAFC technologies. To surmount the overpotential losses, it is desirable to have NCs to trigger the FAOR as close to the reversible conditions (i.e. with over-potential loss as close to zero as possible). Herein, Pd-based binary and ternary NCs consisting of PdPt and PdRuPt have been synthesized via the polyol reduction method on the carbon support. As prepared PdPt and PdRuPt NCs were further subjected to heat treatment (annealed) in CO (namely PdPt-CO and PdRuPt-CO) and O2 (namely PdPt-O2 and PdRuPt-O2) atmosphere at 473 K temperature. By cross-referencing results of electron microscopy and X-ray spectroscopy together with electrochemical analysis, the effects of heat treatment under CO-reductive and O2-oxidative conditions towards FAOR were schematically elucidated. Of special relevance, the mass activity (MA) of PdPt-CO, PdPt-O2, PdRuPt-CO, and PdRuPt-O2 NCs is 1.7/2.0, 1.3/2.2, 1.1/5.5, and 0.9/4.7 Amg−1 in the anodic/cathodic scan, respectively, which is 2~4-folds improved comparative to of as-prepared PdPt (1.0/1.9 Amg−1 in anodic/cathodic scan, respectively) and PdRuPt (0.9/1.4 Amg−1 in anodic/cathodic scan, respectively) NCs. Meanwhile, after chronoamperometric (CA) stability test up to 2000 s, PdPt-CO (72 mAmg−1) and PdRuPt-CO (213 mAmg−1) NCs exhibit higher MA compared to as-prepared PdPt (54 mAmg−1) and PdRuPt (62 mAmg−1) NCs, which is attributed to the increase of surface Pt composition, especially for PdRuPt-CO NC. Besides, the stability of PdPt-O2 (15 mAmg−1) and PdRuPt-O2 (22 mAmg−1) NCs is deteriorated as compared to that of as-prepared NCs due to severe oxidation in O2 atmosphere. Of utmost importance, we developed a ternary PdRuPt catalyst with ultra-low Pt content (~2 wt.%) and significantly improved FAOR performance than pure Pt catalysts. Moreover, we demonstrated that the FAOR performance can be further enhanced by more than 30% via a unique CO annealing treatment.

“…Homogeneous alloy and core–shell structures are common designs combining the bifunctional mechanism, ligand effects, and lattice strain in heterogeneous NCs. , In the consideration of fabrication cost and performance, both designs were extensively studied on bimetallic NCs in long-range ordered and random distributed atomic structures as well as the transition metal core capping by a few monolayers of Pt atoms. Effective strategies by adopting Co, Fe, and Cu as the second element were proposed in the previous reports; however, an improvement in the ORR performance is limited due to the competition of intermediate species (O*, OH – *, and H 2 O*) between reaction sites with identical chemical activity and selectivity on the NC surface. − In addition, the Pt loading is limited to the formation of a monolayer over the core-crystal underneath.…”

Section: Introductionmentioning

confidence: 99%

Pt-Mediated Interface Engineering Boosts the Oxygen Reduction Reaction Performance of Ni Hydroxide-Supported Pd Nanoparticles

ACS Appl. Mater. Interfaces

Yan

Hiraoka

et al. 2023

Self Cite

Fuel cells are considered potential energy conversion devices for utopia; nevertheless, finding a highly efficacious and economical electrocatalyst for the oxygen reduction reaction (ORR) is of great interest. By keeping this in view, we have proposed a novel design of a trimetallic nanocatalyst (NC) comprising atomic Pt clusters at the heterogeneous Ni(OH) 2 -to-Pd interface (denoted NPP-70). The as-prepared material surpasses the commercial J.M.-Pt/C (20 wt %) catalyst by ∼ 166 and ∼19 times with exceptionally high specific and mass activities of 16.11 mA cm −2 and 484.8 mA mg Pt −1 at 0.90 V versus reversible hydrogen electrode (RHE) in alkaline ORR (0.1 M KOH), respectively. On top of that, NPP-70 NC retains nearly 100% performance after 10k accelerated durability test (ADT) cycles. The results of physical characterization and electrochemical analysis confirm that atomicscale Pt clusters induce strong lattice strain (compressive) at the Ni(OH) 2 -to-Pd interface, which triggers the electron relocation from Ni to Pt atoms. Such charge localization is vital for O 2 splitting on surface Pt atoms, followed by the relocation of OH − ions from the Pd surface. Besides, a sharp fall down in ORR performance (mass activity is 37 mA mg Pt −1 at 0.90 V versus RHE) is observed when the Pt clusters are decorated on the surface of NiO x and Pd (denoted NPP-RT). In situ partial fluorescence yield mode X-ray absorption spectroscopy (PFY-XAS) was employed to reveal the ORR pathways on both configurations. The obtained results demonstrate that interface engineering can be a potential approach to boost the electrocatalytic activity of metal hydroxide/ oxide-supported Pd nanoparticles and in turn allow Pd to be a promising alternative for commercial Pt catalysts.