8 Search Results

While nanoscale mimics of peroxidase have been extensively developed over the past decade or so, their catalytic efficiency as a key parameter has not been substantially improved in recent years. Herein, we report a class of highly efficient peroxidase mimic–nickel–platinum nanoparticles (Ni–Pt NPs) that consist of nickel-rich cores and platinum-rich shells. The Ni–Pt NPs exhibit a record high catalytic efficiency with a catalytic constant (K_cat) as high as 4.5 × 10⁷ s^–1, which is ~46- and 10⁴-fold greater than the K_cat values of conventional Pt nanoparticles and natural peroxidases, respectively. Density functional theory calculations reveal that the unique surface structuremore » of Ni–Pt NPs weakens the adsorption of key intermediates during catalysis, which boosts the catalytic efficiency. Furthermore, the Ni–Pt NPs were applied to an immunoassay of a carcinoembryonic antigen that achieved an ultralow detection limit of 1.1 pg/mL, hundreds of times lower than that of the conventional enzyme-based assay.« less

While various effects of physicochemical parameters (e.g., size, facet, composition, and internal structure) on the catalytic efficiency of nanozymes (i.e., nanoscale enzyme mimics) have been studied, the strain effect has never been reported and understood before. Herein, we demonstrate the strain effect in nanozymes by using Pd octahedra and icosahedra with peroxidase-like activities as a model system. Strained Pd icosahedra were found to display 2-fold higher peroxidase-like catalytic efficiency than unstrained Pd octahedra. Theoretical analysis suggests that tensile strain is more beneficial to OH radical (a key intermediate for the catalysis) generation than compressive strain. Pd icosahedra are more activemore » than Pd octahedra because icosahedra amplify the surface strain field. As a proof-of-concept demonstration, the strained Pd icosahedra were applied to immunoassay of biomarkers, outperforming both unstrained Pd octahedra and natural peroxidases. The findings in this research may serve as a strong foundation to guide the design of high-performance nanozymes.« less

Abstract Efficient electro‐oxidation of formic acid, methanol, and ethanol is challenging owing to the multiple chemical reaction steps required to accomplish full oxidation to CO ₂ . Herein, a ternary CoPtAu nanoparticle catalyst system is reported in which Co and Pt form an intermetallic L1 ₀ ‐structure and Au segregates on the surface to alloy with Pt. The L1 ₀ ‐structure stabilizes Co and significantly enhances the catalysis of the PtAu surface towards electro‐oxidation of ethanol, methanol, and formic acid, with mass activities of 1.55 A/mg _Pt , 1.49 A/mg _Pt , and 11.97 A/mg _Pt , respectively in 0.1  m HClO ₄more » . The L1 ₀ ‐CoPtAu catalyst is also stable, with negligible degradation in mass activities and no obvious Co/Pt/Au composition changes after 10 000 potential cycles. The in situ surface‐enhanced infrared absorption spectroscopy study indicates that the ternary catalyst activates the C−C bond more efficiently for ethanol oxidation.« less

Abstract Efficient electro‐oxidation of formic acid, methanol, and ethanol is challenging owing to the multiple chemical reaction steps required to accomplish full oxidation to CO ₂ . Herein, a ternary CoPtAu nanoparticle catalyst system is reported in which Co and Pt form an intermetallic L1 ₀ ‐structure and Au segregates on the surface to alloy with Pt. The L1 ₀ ‐structure stabilizes Co and significantly enhances the catalysis of the PtAu surface towards electro‐oxidation of ethanol, methanol, and formic acid, with mass activities of 1.55 A/mg _Pt , 1.49 A/mg _Pt , and 11.97 A/mg _Pt , respectively in 0.1  m HClO ₄more » . The L1 ₀ ‐CoPtAu catalyst is also stable, with negligible degradation in mass activities and no obvious Co/Pt/Au composition changes after 10 000 potential cycles. The in situ surface‐enhanced infrared absorption spectroscopy study indicates that the ternary catalyst activates the C−C bond more efficiently for ethanol oxidation.« less

We report in this article a detailed study on how to stabilize a first-row transition metal (M) in an intermetallic L1₀-MPt alloy nanoparticle (NP) structure and how to surround the L1₀-MPt with an atomic layer of Pt to enhance the electrocatalysis of Pt for oxygen reduction reaction (ORR) in fuel cell operation conditions. Using 8 nm FePt NPs as an example, we demonstrate that Fe can be stabilized more efficiently in a core/shell structured L1₀-FePt/Pt with a 5 Å Pt shell. The presence of Fe in the alloy core induces the desired compression of the thin Pt shell, especially themore » 2 atomic layers of Pt shell, further improving the ORR catalysis. This leads to much enhanced Pt catalysis for ORR in 0.1 M HClO₄ solution (both at room temperature and 60°C) and in the membrane electrode assembly (MEA) at 80°C. The L1₀-FePt/Pt catalyst has a mass activity of 0.7 A/mg_Pt from the half-cell ORR test and shows no obvious mass activity loss after 30,000 potential cycles between 0.6 V and 0.95 V at 80°C in the MEA, meeting the DOE 2020 target (<40% loss in mass activity). Here, we are extending the concept and preparing other L1₀-MPt/Pt NPs, such as L1₀-CoPt/Pt NPs, with reduced NP size as a highly efficient ORR catalyst for automotive fuel cell applications.« less

Stabilizing a 3d-transition metal component M from an MPd alloy structure in an acidic environment is key to the enhancement of MPd catalysis for various reactions. Here we show a strategy to stabilize Cu in 5 nm CuPd nanoparticles (NPs) by coupling the CuPd NPs with perovskite-type WO_2.72 nanorods (NRs). The CuPd NPs are prepared by controlled diffusion of Cu into Pd NPs and the coupled CuPd/WO_2.72 are synthesized by growing WO_2.72 NRs in the presence of CuPd NPs. The CuPd/WO_2.72 can stabilize Cu in 0.1 M HClO4 solution and, as a result, they show Cu, Pd composition dependent activitymore » for the electrochemical oxidation of formic acid in 0.1 M HClO₄ + 0.1 M HCOOH. Among three different CuPd/WO_2.72 studied, the Cu₄₈Pd₅₂/WO_2.72 is the most efficient catalyst with its mass activity reaching 2086 mA/mgPd in a broad potential range of 0.40 to 0.80 V (vs. RHE) and staying at this value after the 12 h chronoamperometry test at 0.40 V. The synthesis can be extended to obtain other MPd/WO_2.72 (M = Fe, Co, Ni), making it possible to study MPd-WO_2.72 interactions and MPd stabilization on enhancing MPd catalysis for various chemical reactions.« less

Here, we report an electrochemical method to deposit atomic scale Pt on a 5 nm Au nanoparticle (NP) surface in N₂-saturated 0.5 M H₂SO₄. Furthermore, Pt is provided by the Pt wire counter electrode via one-step Pt wire oxidation, dissolution, and deposition realized by controlled electrochemical scanning. Scanning from 0.6–1.0 V (vs. RHE) for 10 000 cycles gives Au_98.2Pt_1.8, which serves as an excellent catalyst for the formic acid oxidation reaction, showing 41 times higher specific activity (20.19 mA cm^-2) and 25 times higher mass activity (10.80 A mg_Pt^-1) with much better CO-tolerance and stability than commercial Pt. This workmore » demonstrates a unique strategy to minimize the use of Pt as a catalyst for electrochemical reactions.« less

In this work, we synthesize a new type of hybrid Pd/WO_2.72 structure with 5 nm Pd nanoparticles (NPs) anchored on 50 × 5 nm WO_2.72 nanorods. The strong Pd/WO_2.72 coupling results in the lattice expansion of Pd from 0.23 to 0.27 nm and the decrease of Pd surface electron density. As a result, the Pd/WO_2.72 shows much enhanced catalysis toward electrochemical oxidation of formic acid in 0.1 M HClO₄; it has a mass activity of ~1600 mA/mg_Pd in a broad potential range of 0.4–0.85 V (vs RHE) and shows no obvious activity loss after a 12 h chronoamperometry test atmore » 0.4 V. Our work demonstrates an important strategy to enhance Pd NP catalyst efficiency for energy conversion reactions.« less