PtCu Nanoframes Research Articles

Structural evolution of PtCu nanoframe for efficient oxygen reduction reactions

• Synthesis of high-active PtCu nanoframes for oxygen reduction reaction. • Synergistic interaction of PtCu nanoframes has excellent electrocatalytic performance. • The etched PtCu nanoframes shows high stability in durability tests. Advances in proton exchange membrane fuel cells require Pt-based catalysts with high catalytic activity and stability. However, due to the expensiveness of Pt, scholars are mainly finding ways to improve the catalytic performance and decrease Pt usage. In this paper, the synthesis of high-active PtCu alloy nanoframes is reported. The nanoframes are prepared by the electric displacement reaction between the Cu nanoplate (Cu NP) template and the Pt precursor, and the high-active PtCu alloy nanoframes are obtained by further etching. The synergistic effect of alloy PtCu nanoframes shows excellent electrocatalytic performance for oxygen reduction reactions, with PtCu high-active nanoframes(PtCu HNF) having approximately 1.4 times the mass activity of commercial Pt/C and exhibiting high stability and tolerance in acidic ORR. Due to the increase in the number of surface active sites and the synergistic effect of bimetals, the activity and stability of the catalyst are significantly improved.

Concave octahedral PtCu nanoframes mediated synergetic photothermal and chemodynamic tumor therapy

Hypoxia regulation by drug delivery nanocargo is an unprecedented strategy for overcoming the inherent vices of traditional tumor treatments. Particularly, stimuli-responsive nanomaterials which are sensitive to external physical stimuli (light, ultrasound, magnetic field, etc.) are greatly desired to realize controllable drug release at tumor lesions and to avoid undesirable drug leakage during the delivery process. Herein, a photothermal mediated ROS self-enhanced CDT nanoplatform is developed as anti-tumor nanoagents by Vitamin C (VC) loaded concave octahedral PtCu nanoframes (COPtCu-Ns). Typically, VC has been proved to be a promising pro-oxidant for the generation of H2O2 and causing selective toxicity to tumor cells rather than normal cells. Simultaneously, the COPtCu-Ns possess Fenton-like catalytic activity in the acidic tumor microenvironment and generate the advanced ROS substance (hydroxyl radical, •OH) subsequently, which causes more serious damage to tumor cells. The as-designed system shows good biocompatibility and bloodcompatibility, quick elimination, and no obvious tissue toxicity both in vitro and in vivo for synergistic PTT and CDT tumor therapy.

Concave Octahedral Ptcu Nanoframes Mediated Synergetic Photothermal and Chemodynamic Tumor Therapy

Concave Octahedral Ptcu Nanoframes Mediated Synergetic Photothermal and Chemodynamic Tumor Therapy

Surface Composition Engineering of PtCu Nanoframe Catalyst to Improve Electrochemical Stability for Oxygen Reduction Reaction

Alloy nanoframes have drawn wide attention in the field of electrocatalysis because of their high specific surface area, molecule accessible 3D pore structure, and excellent catalytic performance. However, due to abundant edges and corners, nanoframes are easy to collapse during the catalytic process, especially for oxygen reduction reaction. Herein, PtCu nanoframes are prepared through wet-chemical method and modified with Mo (Mo-PtCu NF) on the surface to improve the structural stability. Fully open nanoframe catalyst (A-Mo-PtCu NF/C) is finally obtained by selective etching excess Cu in Mo-PtCu NFs. Due to the synergistic effect of Cu and Mo, the electronic structure of Pt in A-Mo-PtCu NF/C is optimized to weaken the oxygen affinity. Meanwhile, the highly open structure of A-Mo-PtCu NF/C provides a large electrochemically active area. Therefore, the as-prepared nanoframe catalysts show enhancements in both mass activity and specific activity compared to the commercial Pt/C catalyst. Moreover, Mo-doping also stabilizes the structure and composition of the nanoframes, enhancing the stability for oxygen reduction reaction. Our research provides an effective strategy to improve the stability of highly active alloy nanoframes.

Structure evolution of PtCu nanoframes from disordered to ordered for the oxygen reduction reaction

Crystal structure engineering of platinum (Pt) based disordered alloys to chemically ordered intermetallics has triggered increasing attention in promoting their performance towards the oxygen reduction reaction (ORR). However, a systematic experiment of comparing the catalytic performance in different crystal structures is rarely reported. Herein, the widely-watched PtCu nanoframes (atomically disordered) are firstly synthesised to investigate their structure-properties relationship. Subsequently, rhombohedral PtCu intermetallics (L11 structured, atomically ordered) which were rarely reported before are fabricated by appropriate high temperature treatment. The L11-PtCu delivers significantly enhanced durability (only 15 % attenuation after 30,000 cycles) while decreased initial activity (0.44 A mgPt−1) for ORR compared with their disordered counterpart. In virtue of in-situ STEM experiment assisted by the state-of-the-art 3D tomography, we reveal that the ordering process improves the resistance against Cu leaching meanwhile results in the collapse and aggregation of the NFs. This work provides a visual understanding of Pt based electrocatalyst in different crystal structures for proton exchange membrane fuel cells in the future.

Intermetallic PtCu Nanoframes as Efficient Oxygen Reduction Electrocatalysts.

Nanoframe alloy structures represent a class of high-performance catalysts for the oxygen reduction reaction (ORR), owing to their high active surface area, efficient molecular accessibility, and nanoconfinement effect. However, structural and chemical instabilities of nanoframes remain an important challenge. Here, we report the synthesis of PtCu nanoframes constructed with an atomically ordered intermetallic structure (O-PtCuNF/C) showing high ORR activity, durability, and chemical stability. We rationally designed the O-PtCuNF/C catalyst by combining theoretical composition predictions with a silica-coating-mediated synthesis. The O-PtCuNF/C combines intensified strain and ligand effects from the intermetallic PtCu L11 structure and advantages of the nanoframes, resulting in superior ORR activity to disordered alloy PtCu nanoframes (D-PtCuNF/C) and commercial Pt/C catalysts. Importantly, the O-PtCuNF/C showed the highest ORR mass activity among PtCu-based catalysts. Furthermore, the O-PtCuNF/C exhibited higher ORR durability and far less etching of constituent atoms than D-PtCuNF/C and Pt/C, attesting to the chemically stable nature of the intermetallic structure.

Paper-based electrochemiluminescence determination of streptavidin using reticular DNA-functionalized PtCu nanoframes and analyte-triggered DNA walker.

A paper-based electrochemiluminescence (ECL) biosensor characterized by the signal amplification of reticular DNA-functionalized PtCu nanoframes (DNA-PtCuTNFs) and analyte-triggered DNA walker was developed for sensitive streptavidin assay. Silver microflower functionalized paper-based sensing platform was prepared to fix the hairpin strand (S1). With addition of the streptavidin, plenty of DNA walkers consisting of the walking strands (S2) labeled with biotin and streptavidin were established, which protected S2 from digestion via theterminal protection mechanism. The sequential introduction of the DNA walker and capture probe initiated the hairpin structure opening of S1 and strand displacement reaction (SDR) happening, causing the S2 release. Subsequently, S1 hybridized with S3. The free S2 furtherhybridized with adjacent S1 to trigger the next cycle. After multiple cycles, the DNA-PtCuTNFs, the fire-new signal enhancer, with remarkable peroxidase activity, were successfully attached onto the paper electrode via metal-catalyst-free click chemistry. Based on the SDR of the DNA walker and the catalysis of DNA-PtCuTNFs, a significantly boosted ECL signal of luminol was obtained. Under the optimal conditions, the developed sensor for streptavidin assay exhibited a low detection limit of 33.4 fM with a linear range from 0.1 pM to 0.1μM. Graphical abstract.

In-Situ Heating and TEM Characterization of Pt-Cu Nanoframes

Increasing the atomic utilization and catalytic activity of Pt is an effective way to promote the commercial application of fuel cells. In this paper, platinum-copper nanoframes (Pt-Cu NFs) were prepared by a simple solvothermal method. For electrocatalytic activity, the Pt-Cu NFs exhibit enhanced oxygen reduction activity due to the unique open structure, electronic effect and geometric effect regulation. However, the dissolution of the transition metal Cu leads to a rapid decay of its stability, which is unable to adapt to long-term operation. Further improvement of its stability is highly desired. Thus, we have attempted to prepare Pt-Cu intermetallic compounds to achieve the phase transition from disordered alloys to ordered intermetallic to enhance their catalytic stability. The results show that the high temperature treatment can achieve its transformation into an ordered phase, and the stability is improved to a large extent, but the activity is reduced because of the aggregation during the high temperature treatment thus the structure was difficult to maintain. In order to explore the structural evolution in the process of ordering, in-situ electron microscopy is used to characterize the structural change trend in the heating process, and it is expected to provide guidance and help for the follow-up works. Figure 1 is here. Figure 1. In-situ TEM observation of Pt-Cu NFs during heating treatment. Keywords: Oxygen Reduction Reaction, Pt-Cu Nanoframes, Intermetallics, In-situ heating

PtCu nanoframes as ultra-high performance electrocatalysts for methanol oxidation

Despite tremendous progress has been achieved in the past two decades, the lack of high-performance catalysts suitable for long-term operation remains a great challenge in realizing the commercial application of direct methanol fuel cell technology. Here, we reported a simple approach for one-pot synthesis of PtCu alloy nanoframes along with their exciting electro-catalytic performance for methanol oxidation. PtCu alloys with highly-open nanoframe structures have been achieved in presence of a structure-directing agent like polyvinyl pyrrolidone (PVP) and reducing solvent like sodium borohydride. Such PtCu alloy nanoframes show tremendous improvement in the methanol electrooxidation with a highest mass activity of 1.64 A mgPt−1 (much lower onset potential compared to Pt alone), which is believed to be much higher compared to that of the commercial Pt/C catalyst and most of the literature reports, indicating a better alloy formation and highly active sites created by highly open nanoframes structures.

L-proline assisted solvothermal preparation of Cu-rich rhombic dodecahedral PtCu nanoframes as advanced electrocatalysts for oxygen reduction and hydrogen evolution reactions

Alloying Pt with earth-abundant metal (e.g. Cu, Ni and Co) can largely improve catalytic activity of Pt-based alloyed nanocrystals by down-shifting the Pt d-band center and modulating the final size, morphology and structure. Herein, Cu-rich rhombic dodecahedral PtCu nanoframes (NFs) were obtained via a one-pot solvothermal route with l-proline and cetyltrimethylammonium chloride (CTAC) as co-structure-directing and stabilizing agents, along with OAm as the reductant. The as-prepared Pt24Cu76 NFs were identified as bifunctional catalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in alkaline electrolyte. Specifically, the catalyst showed excellent catalytic activity and durability for ORR with positive half-wave potential at 0.95 V, outperforming that of commercial Pt/C (20 wt%, 0.88 V). Besides, it exhibited dramatically enhanced HER activity with the more positive potential at 10 mA cm−2 and smaller Tafel slope (−18 mV, 52 mV dec−1) relative to those of Pt/C (−63 mV, 69 mV dec−1). All the results demonstrate the practical applications of robust PtCu electrocatalysts in energy conversion and storage.

Galvanic replacement mediated 3D porous PtCu nano-frames for enhanced ethylene glycol oxidation.

Three dimensional (3D) porous PtCu nano-frames with a unique hollow structure were obtained after a galvanic replacement reaction, exhibiting a high normalized mass activity of 23.1 A m-2 μg-1 towards ethylene glycol oxidation with excellent stability. The morphological evolution and catalytic mechanism were detailed.

A novel electrochemical immunosensor for highly sensitive detection of prostate-specific antigen using 3D open-structured PtCu nanoframes for signal amplification

Herein, a novel electrochemical ultrasensitive immunosensor was designed for detecting prostate-specific antigen (PSA) with three-dimensional (3D) PtCu hollow nanoframes (PtCu HNFs) as signal amplification. The highly opened PtCu HNFs were synthesized by a one-pot solvothermal method with cetyltrimethylammonium chloride (CTAC) and trishydroxymethyl aminomethane (Tris) as co-structuring directors. The architectures enlarged the loading of prostate specific antibodies (Ab) and efficiently catalyzed hydrogen peroxide (H2O2) reaction, ultimately amplifying the signals. And polylysine was used to disperse PtCu HNFs, improve the biocompatibility and bind the Ab on the electrode surface. The fabricated immunosensor exhibited lower detection limit (0.003 ng mL–1, S/N = 3), and wider linear range (0.01–100.0 ng mL–1), along with the improved reproducibility, selectivity and stability for the assay of PSA. Thus, it is a desirable platform for PSA detection in clinical diagnosis and practical applications.

Two-step etching fabrication of tunable ternary rhombic dodecahedral nanoframes for enhanced oxygen reduction electrocatalysis

The shape-tunable PtCuNi rhombic dodecahedra nanoframe is achieved via modified solvothermal and two-step etching, the first step is PtCuNi concave rhombic dodecahedra synthetized due to oxidation etching, and the second step is PtCuNi nanoframes obtained through the acid etching. The PtCuNi solid rhombic dodecahedra as an intermediate product can be well controlled by adjusting the amount of reaction time and Ni precursor. Based on the formation mechanism of PtCu nanoframes, the morphological evolution process of ternary nanoframe is precisely investigated according to the changes of morphology, atomic ratio and average particle size. In addition, shape-tunable PtCuNi nanoframes catalyst shows enhanced mass activity of 0.86 A mg−1Pt at 0.9 V versus reversible hydrogen electrode towards oxygen reduction reaction, which is 6 times as well as that of the commercial Pt/C catalyst. Remarkably, there is a more positive onset potential of PtCuNi nanoframes compared to other catalysts. More importantly, this synthetic method opens a promising door towards development and applications of Pt based catalysts.

Photoelectrochemical biosensor for HEN1 RNA methyltransferase detection using peroxidase mimics PtCu NFs and poly(U) polymerase-mediated RNA extension

2′-O-methyl group on the 3′ terminal nucleotide in plant microRNAs, as one kind of RNA methylations, is caused by HEN1 RNA methyltransferase (HENMT1), which is thought to be crucial for ribosome biogenesis and function. Herein, a simple and label-free PEC biosensing method was proposed for assay of HENMT1 activity and inhibitor screening based on peroxidase mimic PtCu nanoframes (PtCu NFs) catalytic signal amplification. In this work, MoS2@Graphene quantum dots/Phosphorus-doped rodlike carbon nitride (MoS2@GQDs/P-RCN) heterojunction was used as photoactive materials. With the doping of GQDs and the formation of heterojunction, the photoactivity of MoS2 is greatly improved. After the double-stranded RNA (dsRNA) with 2 nt 3′ overhangs was treated with HENMT1 in the presence of S-adenosyl-L-methionine, the 3′ terminal nucleotide of the unmethylated dsRNA could be extended under the catalysis of the poly(U) polymerase in the existence of UTP. Poly(A) nucleotide chain modified with carboxyl group was captured on the electrode surface through hybridization reaction and acted as a bridge for the immobilization of reticular DNA-functionalized PtCu NFs (PtCu@DNA). Under the catalysis effect of peroxidase mimics PtCu@DNA towards hydrogen peroxide, O2- was in situ generated as electron donor and a strong photocurrent was obtained. The proposed PEC bioassay exhibited high selectivity and low detection limit of 3.36ng/mL for HENMT1 activity assay. Furthermore, the inhibition research indicated that chlorpyrifos could inhibit the HENMT1 activity with the IC50 value of 48.32nM.

Concave Platinum-Copper Octopod Nanoframes Bounded with Multiple High-Index Facets for Efficient Electrooxidation Catalysis.

Multimetallic nanoframes with three-dimensional (3D) catalytic surfaces represent an emerging class of efficient nanocatalysts. However, it still remains a challenge in engineering nanoframes via simple and economical methods. Herein, we report a facile one-pot synthetic strategy to synthesize Pt-Cu nanoframes bounded with multiple high-index facets as highly active electrooxidation catalysts. Two distinct octopod nanoframes, namely, concave PtCu2 octopod nanoframes (PtCu2 CONFs) and ultrathin PtCu octopod nanoframes (PtCu UONFs) were successfully synthesized by simply changing the feeding Pt and Cu precursors. Interestingly, the PtCu2 CONFs are constructed by eight symmetric feet with sharp tips, which are enclosed by high-index facets of n (111)-(111), such as {553}, {331}, and {221}. Benefiting from their 3D accessible surfaces and multiple high-index facets, the self-supported PtCu2 CONFs catalysts exhibit excellent electrocatalytic performance and superior CO-tolerant ability. For methanol oxidation reaction, the PtCu2 CONFs catalysts exhibit more than 7-fold increase in activities, 205 mV lower in the onset potential compared with commercial Pt/C. More importantly, when facing harsh electrochemical reaction conditions, the PtCu2 CONFs are well-preserved in the catalytic activities, architectural features, and stepped surfaces. The PtCu UONFs with 12 ultrathin edges, however, suffer from breakdown. The present work provides guidelines for the rational design and synthesis of nanoframe catalysts with both high activity and stability.

One-Pot Synthesis of Highly Anisotropic Five-Fold-Twinned PtCu Nanoframes Used as a Bifunctional Electrocatalyst for Oxygen Reduction and Methanol Oxidation.

Five-fold-twinned PtCu nanoframes (NFs) with nanothorns protruding from their edges are synthesized by a facile one-pot method. Compared to commercial Pt/C catalyst, the obtained highly anisotropic five-fold-twinned PtCu NFs show enhanced electrocatalytic performance toward the oxygen reduction reaction and methanol oxidation reaction under alkaline conditions.

Platinum-Copper Nanoframes: One-Pot Synthesis and Enhanced Electrocatalytic Activity.

Platinum-copper nanoframes were produced from copper nanoparticles by a one-pot synthesis method. The growth mechanism was thoroughly studied by experiment and theoretical calculations. Owing to the unique structure, Pt-Cu nanoframes exhibited significantly enhanced catalytic activity toward the electro-oxidation of methanol compared to commercial Pt black.

Highly open rhombic dodecahedral PtCu nanoframes.

Herein, we report a facile strategy that allows one-pot preparation of highly open rhombic dodecahedral PtCu alloy nanoframes. Due to the highly open structures, the PtCu nanoframes exhibit enhanced catalytic performance in methanol electrooxidation, showing a new strategy to create highly active catalysts.