Sorbitol electro-oxidation reaction on sub<10 nm PtAu bimetallic nanoparticles

Single atom alloys aggregation in the presence of ligands

Single atom alloys (SAAs) have gained tremendous attention as promising materials with unique physicochemical properties, particularly in catalysis. The stability of SAAs relies on the formation of a single active dopant on the surface of a metal host, quantified by the surface segregation and aggregation energy. Previous studies have investigated the surface segregation of non-ligated and ligated SAAs to reveal the driving forces underlying such phenomena. In this work we address another key factor dictating the stability in non-ligated and ligated SAAs: the aggregation energy (Eagg) of dopants. Specifically, we examine how thiols and amines, commonly found ligands in colloidal bimetallic nanoparticle synthesis, affect the aggregation of dopants (forming dimers and trimers) on the surface of a metal host. Utilizing Density Functional Theory (DFT) and machine learning (ML), we explore the stability patterns of SAAs through the energetics of low-index surfaces, such as (111) and (100), consisting of d8-(Pt, Pd, Ni) and d9-(Ag, Au, Cu) metals, both in the presence and absence of ligands. Collecting rich and accurate DFT data, we developed a four-feature support vector regression using the radial basis function (SVR RBF) to predict the Eagg. The model revealed important and easily accessible (tabulated) thermodynamic stability features that drive metal aggregation in SAAs, such as the bulk cohesive energy of the metal considering the exposed coordination environment on the surface, the charge transfer represented by the difference in electron affinities of metals and the radii of the metals describing strain effects. Additional incorporated features include adsorbate properties, such as the binding energy of the ligand on a single atom considering the coordination environment of the adsorbate. Through our study, we have revealed that stable SAAs are formed in Ni-, Pd-, Pt-based SAAs in the presence of ligands, while Ag-, Au-, Cu- doped with Ni-, Pd-, Pt- lead to aggregation. Finally, we tested our model against several experimental studies and demonstrated its robustness in predicting the formation of SAAs, enabling rapid screening across the vast materials space of SAAs. Additionally, we suggest criteria for stabilization of SAAs, guiding experimental efforts. Overall, our study advances the understanding of thermodynamic stability of colloidal SAAs, paving the way for rational SAA design.

Electrochemical and Non-Electrochemical Pathways in the Electrocatalytic Oxidation of Monosaccharides and Related Sugar Alcohols into Valuable Products

In this contribution, we review the electrochemical upgrading of saccharides (e.g., glucose) and sugar alcohols (e.g., glycerol) on metal and metal-oxide electrodes by drawing conclusions on common trends and differences between these two important classes of biobased compounds. For this purpose, we critically review the literature on the electrocatalytic oxidation of saccharides and sugar alcohols, seeking trends in the effect of reaction conditions and electrocatalyst design on the selectivity for the oxidation of specific functional groups toward value-added compounds. Importantly, we highlight and discuss the competition between electrochemical and non-electrochemical pathways. This is a crucial and yet often neglected aspect that should be taken into account and optimized for achieving the efficient electrocatalytic conversion of monosaccharides and related sugar alcohols into valuable products, which is a target of growing interest in the context of the electrification of the chemical industry combined with the utilization of renewable feedstock.

A Smartphone Colorimetric Sensor Based on Pt@Au Nanozyme for Visual and Quantitative Detection of Omethoate

A smartphone colorimetric sensor based on the Pt@Au nanozyme was successfully developed for the visual and quantitative detection of omethoate in fruit and vegetables. The anti-omethoate antibody was conjugated on the surface of the Pt@Au nanozyme as a catalytic functional signal probe, and coating antigen conjugated on the surface of magnetic polystyrene microspheres (MPMs) was used as a separation capture probe. In the sensing system, when the catalytic functional signal probe was combined with a separation capture probe containing no omethoate, the visible blue color appeared with the addition of tetramethylbenzidine (TMB) chromogenic solution, and the maximum B value of the sensing system was obtained via the smartphone. With increasing concentrations of omethoate, the visualization of the sensing system decreased, and the B-value obtained via the smartphone dropped. Under optimal detection conditions, the omethoate could be detected in a linear range of 0.5–50 μg/L (R² = 0.9965), with a detection limit of 0.01 μg/L. The accuracy and reliability of the detection results of this colorimetric sensor were successfully confirmed by enzyme linked immunosorbent assay (ELISA) and gas chromatography. This colorimetric sensor provides a technical reference and potential strategy for the immunoassay of hazard factors in resource-scarce laboratories.

Core@shell PtAuAg@PtAg Hollow Nanodendrites as Effective Electrocatalysts for Methanol and Ethylene Glycol Oxidation

Pt-based catalysts with core@shell structures are widely used in alcohol oxidations due to their excellent catalytic performance. In this work, we synthesized a series of core@shell PtAuAg@PtAg hollow nanodendrites (HNDs) with different compositions by a simple seed-mediated method. The PtAuAg@PtAg HNDs with a hollow core and dendritic shell exhibit excellent catalytic performance for ethylene glycol oxidation reaction (EGOR) and methanol oxidation reaction (MOR). Among these, Pt₃₈Au₂₉Ag₃₃ HNDs have the highest mass activity (12364.0 mA mg_Pt^-1/3278.0 mA mg_Pt^-1) for EGOR and MOR, which is 4.2 times and 5.3 times higher than that of commercial Pt/C (2941.0 mA mg_Pt^-1/617.6 mA mg_Pt^-1), respectively. More importantly, after successive cyclic voltammetry tests, the retained mass activities of Pt₃₈Au₂₉Ag₃₃ HNDs are 3913.8 mA mg_Pt^-1 and 348.3 mA mg_Pt^-1, which are much higher than that of commercial Pt/C as well. The excellent catalytic performance of PtAuAg@PtAg HNDs can be attributed to the structure of HNDs, which can greatly increase the surface area and active sites, as well as the electronic and synergistic effects among Pt, Au, and Ag. This research may provide new ideas for the development of high-efficiency hollow catalytic materials for EGOR and MOR.