Synthesis of Ordered Pt Nanocube Arrays Directed by Block Copolymer Nanotemplate and Their Potential on Ethanol Oxidation Reaction

Advanced Energy Materials

Qing

et al. 2021

101

are more convenient and secure to be transported and stored. However, the conversion efficiencies of these AORs are commonly inferior to hydrogen oxidation. This is partially due to the sluggish kinetics of multielectrons' transferred processes inside alcohols (e.g., methanol, ethanol, ethylene glycol, and glycerol). [7][8][9][10][11] In this regard, various catalysts of both noble and non-noble metals have been designed and synthesized to boost such sluggish AORs. Although noble metal catalysts (e.g., Pd, Pt, and Rh) are more expensive than non-noble metals (e.g., Ni, Co, and Mn), their more negative AOR onset potentials make them superior for the construction of DAFCs, [4,5,11] originating from their unique electronic structures. Among reported noble-based catalysts, those based on the Pt metal are regarded as the star electrocatalysts for the AORs in terms of their oxidation overpotentials and Tafel slopes. [12,13] Notably, their alloys with other metals (e.g., Ru, Ni, Co, Pd, Rh, and Au) exhibit strong adsorption capability toward OH species or a so-called bifunctional mechanism, leading to improved AOR performance. [14][15][16][17] On the other hand, the serious poisoning effect of the carbonaceous intermediates (especially CO) hinders dramatically the activity of the used catalysts (especially the Pt catalysts) and eventually leads to much reduced conversion efficiencies of the AORs. [18,19] In this context, the screwlike PdPt alloy nanowires [19] and PdPt alloy nanoparticles [20] have been employed to replace single metallic Pt catalysts for methanol electro-oxidation reaction (MOR). Originating from varied electronic structures that are induced by the addition of Pd atoms, these PdPt alloys have been confirmed as commendable MOR catalysts. Although the sizes and compositions of these catalysts have been tuned and the AOR performance on these catalysts has been explored, the performance of these bimetallic heterostructures/catalysts is still far away for their commercial applications. The catalysts featuring superior AOR performance over those reported are still highly demanded for the construction of high-performance DAFCs.It has been well known that the optimization of these noble-metallic heterostructures/catalysts with respect to their morphologies and exposed facets is helpful to enhance their catalytic performance. [21][22][23][24] Among various heterostructures, a catalyst with a core-shell structure has been attracted special attention. [25][26][27][28][29][30] Its structure and its catalytic activity of the shell are revealed to be highly dependent on the used core. [31][32][33][34] This is because the strain effect (expansion or compression) can be Direct alcohol fuel cells (DAFCs) utilize alcohol electro-oxidation reactions (AORs) to provide electricity, where catalysts with optimal electronic structures are required to accelerate sluggish AORs. Herein, an electrocatalyst with an Au-nanorod core and a PdPt-alloy shell is designed. Its electronic structures are modulated through epitaxial growth ...

Section: Introductionmentioning

confidence: 99%

Modulating Electronic Structure of an Au‐Nanorod‐Core–PdPt‐Alloy‐Shell Catalyst for Efficient Alcohol Electro‐Oxidation

Advanced Energy Materials

Qing

et al. 2021

101

“…The SEM image of a PtCo/BCP nodule is provided in Figure b, which shows that the higher PtCo core is surrounded by the lower flat polymer domains. Subsequently, the polymer can be removed and the PtCo alloys will be simultaneously reduced under the H 2 /Ar plasma. , The center-to-center distance and the average diameter are ∼43 and ∼22 nm, respectively (Figure c). Note that the hexagonally arranged PtCo NPs (in Figure c) are consistent with the parent PtCo/BCP nodules (in Figure a), indicating that the self-assembly of the BCP directs the PtCo NPs into ordered nanoarrays.…”

Section: Resultsmentioning

confidence: 99%

“…Integrating with other metals to prepare Pt–M alloys is one feasible way to address these difficulties for the Pt-based catalysts. − Core–shell structure NPs with Pt as shells attract much attention for the low Pt loading and the promotion on ORR activity. − However, most of the core–shell NPs are prepared by solution-phase synthesis requiring complicated conditions. − The template- and scaffold-assisted fabrication of NP arrays through block copolymers (BCPs) interests researchers with the large-scale morphologies in controllable distributions, shapes, and sizes. − The microphase segregation of BCP blocks can compartmentalize the NPs into the interfaces between the different polymer chains or the microdomains of the polymers. − As a result, the BCP approach is capable of fabricating highly ordered metal NP arrays fulfilling the requirements for a variety of practical applications. − …”

Section: Introductionmentioning

confidence: 99%

Highly Ordered Pt-Based Nanoparticles Directed by the Self-Assembly of Block Copolymers for the Oxygen Reduction Reaction

Mai

ACS Appl. Mater. Interfaces

et al. 2021

Self Cite

Designing Pt-based nanoparticle (NP) catalysts is of great interest for the lowering of Pt usage and the enhancement of catalytic activity on the proton-exchange membrane fuel cells (PEMFCs). However, it is still challenging to develop well-arrayed catalyst NPs on supports over multiple-length scales. Herein, we presented a facile strategy of producing well-ordered Pt-based NPs toward oxygen reduction reaction (ORR) catalysts assisted by the self-assembly of block copolymers. In contrast to the conventional Pt/C ORR catalysts with a random dispersion on carbon, the as-prepared Pt, PtCo, and PtCo@Pt NPs in our work were hexagonally arranged with a uniform quasi-spherical shape and ordered distribution. The systematic study related to their ORR activities revealed that the PtCo@Pt core−shell NP arrays were more active and more durable than PtCo, Pt, and the commercial Pt/C catalyst. In the rotating-disk electrode test, a half-wave potential (E 1/2 ) of 0.86 V versus RHE and a 4-e ORR mechanism were found for PtCo@Pt. Single-cell performance showed that the current density and the peak power density of PtCo@Pt achieved 0.86 A/cm 2 @0.7 V and 1.05 W/cm 2 , respectively, with a Pt loading of ∼0.15 mg/cm 2 on the cathode. Also, they held 81.4 and 82.9% retention, respectively, after the durability test in the single-cell test. Density functional theory calculation results revealed that PtCo@Pt NPs had a lower dband center and a weaker oxygen binding energy compared to Pt and PtCo, which contributed to the enhancement of the ORR activity.

“…29 For example, it has been reported that hexagonally arranged Pt nanocubes could be generated and that they demonstrate improved electrochemical activities towards ethanol oxidation reduction. 30 In most cases, a single kind of metallic NP was employed with precise control over the size and the shape of the resulting structures as well as the periodicity and symmetry of the structural patterns. 31…”

Section: Introductionmentioning

confidence: 99%

A three-dimensional ordered honeycomb nanostructure anchored with Pt–N active sites via self-assembly of a block copolymer: an efficient electrocatalyst towards the oxygen reduction reaction in fuel cells

et al. 2022

J. Mater. Chem. A

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