Precisely Controlled Synthesis of Pt-Pd Octahedral Nanoframes as a Superior Catalyst towards Oxygen Reduction Reaction

Pt-based nanoframes represent a class of promising catalysts towards oxygen reduction reaction. Herein, we, for the first time, successfully prepared Pt-Pd octahedral nanoframes with ultrathin ridges less than 2 nm in thickness. The Pt-Pd octahedral nanoframes were obtained through site-selected deposition of Pt atoms onto the edge sites of Pd octahedral seeds, followed by selective removal of the Pd octahedral cores via chemical etching. Due to that a combination of three-dimensional opens geometrical structure and Pt-skin surface compositional structure, the Pt-Pd octahedral nanoframes/C catalyst shows a mass activity of 1.15 A/mgPt towards oxygen reduction reaction, 5.8 times enhancement in mass activity relative to commercial Pt/C catalyst （0.20 A/mgPt）. Moreover, even after 8000 cycles of accelerated durability test, the Pt-Pd octahedral nanoframes/C catalyst still exhibits a mass activity which is more than three times higher than that of pristine Pt/C catalyst.

Phase-transfer interface promoted corrosion from PtNi10 nanoctahedra to Pt4Ni nanoframes

A novel two-phase approach towards the corrosion of PtNil0 nanoctahedra has been developed. In this strategy, the active component of Ni in oil-soluble PtNil0 nanoctahedra which resided in the upper toluene phase, suffered from etching and was then transferred into a lower aqueous phase with coordination by ethylenediaminetetraacetate （EDTA）. Due to the existence of the phase-transfer interface promoted by EDTA, the corrosion reaction proceeded at an accelerated rate under the mild conditions. Specifically, the resultant products of octahedral Pt4Ni nanoframes were successfully fabricated for the first time, and PtNi4 porous octahedra could be obtained when the dosage of EDTA-2Na was reduced. After a systematic study of this two-phase system, a ＂synergetic corrosion＂ mechanism is proposed to account for the formation of octahedral Pt4Ni nanoframes, involving contributions from many species （i.e., O2, H2O, H＋, OAm, and EDTA^4-）. As a result of the fascinating three-dimensional geometry of Pt4Ni nanoframes and PtNi4 porous octahedra, both of the corroded nanocrystals showed superior activity over the pristine PtNi^o nanoctahedra for ethanol electrooxidation in alkaline media and hydrogenation of nitrobenzene.

Temperature-controlled fabrication of Co-Fe-based nanoframes for efficient oxygen evolution

Transition metal phosphides(TMPs)have emerged as promising electrocatalysts to enhance the slow kinetic process of oxygen evolution reaction(OER).Framelike hollow nanostructures(nanoframes,NFs)provide the open structure with more accessible active sites and sufficient channels into the interior volume.Here,we report the fabrication of bimetallic Co-Fe phosphide NFs(Co-Fe-P NFs)via an intriguing temperature-controlled strategy for the preparation of precursors followed by phosphidation.The precursors,Co-Fe Prussian blue analogues(Co-Fe PBAs)are prepared by a precipitation method with Co^(2+)and[Fe(CN)_(6)]^(3−),which experience a structural conversion from nanocubes to NFs by increasing the aging temperature from 5 to 35℃.The experimental results indicate that this conversion is attributable to the preferentially epitaxial growth on the edges and corners of nanocubes,triggered by intramolecular electron transfer at an elevated aging temperature.The as-prepared Co-Fe-P NFs catalyst shows remarkable catalytic activity toward OER with a low overpotential of 276 mV to obtain a current density of 10 mA cm^(−2),which is superior to the reference samples(Co-Fe-P nanocubes)and most of the recently reported TMPs-based electrocatalysts.The synthetic strategy can be extended to fabricate Co-Fe dichalcogenide NFs,thereby holding a great promise for the broad applications in energy storage and conversion systems.

Defect-density control of platinum-based nanoframes with high-index facets for enhanced electrochemical properties

Structure-engineered platinum-based nanoframes(NFs)at the atomic level can effectively improve the catalytic performance for fuel cells and other heterogeneous catalytic fields.We report herein,a microwave-assisted wet-chemical method for the preparation of platinum-copper-cobalt NFs with tunable defect density and architecture,which exhibit enhanced activity and durability towards the electro-oxidation reactions of methanol(MOR)and formic acid(FAOR).By altering the reduction/capping agents and thus the nucleation/growth kinetics,trimetallic platinum-copper-cobalt hexapod NFs with different density high-index facets are achieved.Especially,the rough hexapod nanoframes(rh-NFs)exhibit excellent specific activities towards MOR and FAOR,7.25 and 5.20 times higher than those of benchmark Pt/C,respectively,along with prolonged durability.The excellent activities of the rh-NFs are assigned to a synergistic effect,including high density of defects and high-index facets,suitable d-band center,and open-framework structure.This synergistic working mechanism opens up a new way for enhancing their electrocatalytic performances by increasing defect density and high-index facets in open-framework platinum-based NFs.

Peroxidase-like properties of Ruthenium nanoframes

This work reports the inherent peroxidase-like properties of Ruthenium （Ru） nanoframes. After templating with Palladium （Pd） seeds, Ru nanoframes with an octa- hedral shape, average edge length of 6.2 nm, and thickness of 1.8 nm were synthesized in high purity （〉95 %） and good uniformity. Using the oxidation of 3,3t,5,5＇-tetram- ethylbenzidine （TMB） by H202 as a model catalytic reac- tion, the Ru frames were demonstrated to be approximately three times more active than natural peroxidases in cat- alyzing the formation of colored products. As compared to their natural counterparts, Ru frames have a stronger binding affinity to TMB as well as a weaker binding affinity to hydrogen peroxide during the catalysis. The Ru frames as peroxidase mimics proved to be chemically and thermally stable. This work represents the first demonstration of Ru nanostructure-based peroxidase mimics and is therefore expected to inspire future research on bio-applications of Ru nanomaterials.

Facet-selective growth of MOF-on-MOF heterostructures enables etching-free synthesis of highly-open Co/N-doped carbon nanoframes for efficient catalysis

Highly-open nanoframe structures consisting of interconnected and exposed ridges are highly desirable for achieving efficient catalysis,but preparing them by a facile etching-free methodology is still a very daunting task.Herein,we propose a novel metal-organic framework(MOF)-assisted and etching-free strategy for the construction of Co/N-doped carbon nanoframes with highly-open and precisely-controllable structures.This strategy is based on the face-selective epitaxial growth of ZIF-67 on the 36{110}facets of 72-facet ZIF-8 to form an unprecedented anisotropic ZIF-67-on-ZIF-8 heterostructure,which is subsequently pyrolyzed under Ar atmosphere to realize a solid-to-frame transformation.The highly-open nanoframe structure enables the substrates to readily penetrate into the catalyst interior and thereby create additional exposed active sites,which together with the good mass transport,high atomic utilization and increased surface area are responsible for its remarkably enhanced catalytic activity for the biomass valorisation when compared with its solid and closed hollow counterparts.This study could shed valuable insights into the design and preparation of various highly-open nanoframes with abundant exposed active species by using an etching-free strategy for efficient catalysis and beyond.

Porous Pt nanoframes decorated with Bi(OH)3 as highly efficient and stable electrocatalyst for ethanol oxidation reaction

High-quality Pt-based catalysts are highly desirable for ethanol oxidation reaction(EOR),which is of critical importance for the commercial applications of direct ethanol fuel cells(DEFCs).However,most of the Pt-based catalysts have suffered from high cost and low operation durability.Herein a two-step method has been developed to synthesize porous Pt nanoframes decorated with Bi(OH)3,which show excellent catalytic activity and operation durability in both alkaline and acidic media.For example,the nanoframes show a mass activity of 6.87 A·mgPt−1 in alkaline media,which is 13.5-fold higher than that of commercial Pt/C.More importantly,the catalyst can be reactivated simply,which shows negligible activity loss after running for 180,000 s.Further in situ attenuated total reflection-infrared(ATR-IR)absorption spectroscopy and CO-stripping experiments indicate that surface Bi(OH)3 species can greatly facilitate the formation of adsorbed OH species and subsequently remove carbonaceous poison,resulting in a significantly enhanced stability towards EOR.This work may favor the tailoring of desired electrocatalysts with high activity and durability for future commercial application of DEFCs.

Construction of trace silver modified core@shell structured Pt-Ni nanoframe@CeO2 for semihydrogenation of phenylacetylene

The Pt-Ni nanoframe catalysts have attracted great interest owing to their unique electronic structure and excellent catalytic performance. However, the stability of the tenu ous edges of nano frame-structures is dissatisfactory and their un iversal applicati ons in catalytic market beyond electrocatalytic reactions are yet to be tapped and explored. Herein, we developed a new core@ shell structured Pt-Ni nanoframe@CeO2 (Pt-Ni NF@CeO2) composite via etching the Ni from inhomogeneous Pt-Ni rhombic dodecahedra (Pt-Ni RD) by cerium(lll) acetate hydrate (Ce(OAc)3). In this path, Pt-Ni RD was used as self-sacrificial 怕mplate, while the Ce(OAc)3 serves as the provider of the Ce3* source and OH' for the formation of CeO2 shell, etchant of Pt-Ni RD, and the surface modification agent. By this way, the etching of Pt-Ni RD and the formation of the CeO2 shell are simultaneously proceeded to form the final Pt-Ni NF@CeO2 in one step. The obtained Pt-Ni NF@CeO2 exhibits strong in terfacial charge tran sfer interactio n betwee n Pt-Ni NF core and CeO2 shell eve n without reductio n treatment, leading to enhan ced catalytic activity in the hydrogenation of phenylacetylene. After introduction of trace silver, the Pt-Ni-Ag4.9 NF@CeO2 achieves remarkable catalytic performa nee for the selective con versi on of phe ny lacetyle ne to styrene: high con version (100%), styre ne selectivity (86.5%), and good stability. It reveals that enc apsulatio n n oble metal nano frames into metal oxide to form core @ shell structured hybrids will in deed enhance their stability and catalytic properties. Particularly, this work expends the application of noble metal nanoframes materials to hydrogenation reacti ons.

Hierarchical iridium-based multimetallic alloy with double-core-shell architecture for efficient overall water splitting

The overall water splitting for hydrogen production is an effective strategy to resolve the environmental and energy crisis. Here, we report a facile approach to synthesize the Ir-based multimetallic, hierarchical, double-coreshelled architecture(HCSA) assisted by oil bath reaction for boosting overall water splitting in acidic environment. The Ir Ni Cu HCSA shows superior electrocatalytic activity for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER), which are comparable to commercial Pt/C and better than IrO2. The Ir Ni Cu HCSA exhibits remarkably catalytic efficiency as bifunctional catalyst for overall water splitting where a low cell voltage of 1.53 V is enough to drive a current density of 10 mA cm^-2 and maintains stable for at least 20 h. The presented work for the design and synthesis of novel Ir-based multimetallic architecture paves the way for highperformance overall water splitting catalysis.