Element Distributions in Bimetallic Aerogels

Uncovering the electrocatalytic potential of two-dimensional Pt-Ni bimetallic aerogels

Metal aerogels have established themselves as promising materials for various applications across diverse fields, from sensing to soft neural implants. Since they emerged as a distinct class of materials in 2009, catalysis has been one of their most common application areas. However, even after a decade of research on metal aerogels for catalytic purposes, there remains room for improvement. The rising costs associated with production, driven by expensive drying techniques and costly metal precursors, have motivated the scientific community to explore alternative approaches and materials. This work investigates a film-like 2D Pt-Ni aerogel as a potential alternative for the methanol oxidation reaction (MOR). This aerogel was fabricated using a recently reported phase-boundary gelation, which requires a low quantity of metal precursors and avoids the need for special drying techniques. Comparative studies of the 2D and 3D aerogels confirm their structural integrity and the characteristic high porosity. The 2D Pt-Ni aerogel demonstrates a reproducibly high electrochemically active surface area of approximately 50.6 m2 g-1 and an excellent mass activity for MOR of around 1.8 A mg-1, surpassing the 3D Pt-Ni aerogel.

Multi-metal MOF-on-MOF metal-organic gel-based visual sensing platform for ultrasensitive detection of chlortetracycline and D-penicillamine

The widespread presence of antibiotic residues in the environment and food represents a significant threat to human health. In this study, a novel MOF-on-MOF (FCZE) gel with excellent peroxidase activity and strong fluorescence properties successfully synthesized by using Polyvinyl pyrrolidone (PVP) as a cross-linker and H₄BTEC as a ligand. Based on the energy transfer from the FCZE ligand to Eu luminescence, an ultrasensitive fluorescence method was developed for the detection of chlortetracycline (CTC), achieving a limit of detection (LOD) as low as 0.43 nM. Furthermore, the combination of FCZE with the 3,3',5,5'-tetramethylbenzidine (TMB)-hydrogen peroxide (H2O2) system enabled sensitive colorimetric detection of D-penicillamine (D-PA) with an LOD of 8.66 nM. Theoretical calculations reveal that the fluorescence quenching of FCZE by CTC is attributed to the inner filter effect of CTC and its suppression of the H4BTEC excited-state return to the ground state. Furthermore, Fukui function was employed for the first time to clarify the role of D-PA in scavenging free radicals and reducing oxidized TMB (oxTMB), providing a comprehensive understanding of the colorimetric detection mechanism. Additionally, a smartphone-assisted visual detection platform based on FCZE was developed for the detection of CTC and D-PA, with LODs of 0.71 μM and 0.13 μM, respectively. This study highlights the potential of nanomaterials for the simultaneous detection of multiple antibiotics, offering a novel strategy for the rapid and efficient monitoring of antibiotic residues in environmental samples.

Molecularly Woven Polymer Aerogels

Aerogels with abundant nanopores and large specific surface areas have extensive potential in various applications but are constrained by fragility and difficulty in degradation. Currently, the exploration of adaptive and reprocessing aerogels has become increasingly urgent, as the demand for intelligent and sustainable materials intensifies. Here, we present a molecular weaving strategy to construct molecularly woven polymer aerogels (WPAs) via catalyst-free aldimine condensation between prewoven aldehyde-functionalized Cu(I) bisphenanthroline (Cu(PBD)2) and flexible 4,4'-diaminodibenzyl (DB). The key feature of this system consists entirely of dense woven nodes that can be readily activated by external stimuli, where Cu(I) ions can also be reversibly removed as needed, while preserving porous structures. Consequently, we achieve adjustable mechanical properties of WPAs, with a 10-fold enhancement in elasticity after removing Cu(I) ions. Moreover, the destroyed WPAs demonstrate a straightforward reprocessing capacity rather than tedious monomer recovery due to the dissociation of Cu(I)-coordination bonds, the activation of sequential polymer thread motions, and the accelerated imine bond exchange enabled by adjacent Cu(I) ions. This work offers a new perspective on designing customizable and sustainable aerogels and verifies the feasibility of the emergent molecularly woven technique in a more complex functional material system.

Mussel-inspired self-assembly of silver nanoclusters into multifunctional silver aerogels for enhanced catalytic and bactericidal applications

Silver nanoclusters (AgNCs) have shown broad application prospects in catalysis, sensing, and biological fields. However, the limited stability of AgNCs has become the main challenge restricting their practical application in complex environments. Herein, a mussel-inspired, dopamine-assisted self-assembly approach is reported to fabricate 3D AgNC aerogels (PDA/AgNCs), which possess significantly enhanced structural stability and synergistic functional properties. The prepared AgNC aerogels display a hierarchical network structure with an ultrafine ligament size of 10.3 ± 1.2 nm and a high specific surface area of 50.7 m2 g-1. The gelation mechanism is elucidated by in-depth characterization and time-lapse monitoring of the gelation process vis spectroscopic and microscopic approaches. Owing to the distinct features of aerogels and the synergistic effect of AgNCs and PDA, the fabricated aerogels can not only efficiently decolorize dyes with a faster kinetic than individual AgNCs, but also exhibit remarkable broad-spectrum antimicrobial activity. Consequently, a conceptual water-treatment device is established by depositing PDA/AgNC aerogels on the cotton substrate, which shows good performance in both catalytic dye degradation and bacterial killing in the flowing system. This mussel-inspired self-assembly strategy has great potential in developing robust AgNC-based functional materials, which also provides a new guideline for designing sophisticated materials with integrated functions and synergistic properties.

Ligand Effect of PdRu on Pt-Enriched Surface for Glucose Complete Electro-Oxidation to Carbon Dioxide and Abiotic Direct Glucose Fuel Cells

The development of advanced electrocatalysts for the abiotic direct glucose fuel cells (ADGFCs) is critical in the implantable devices in living organisms. The ligand effect in the Pt shell-alloy core nanocatalysts is known to influence the electrocatalytic reaction in interfacial structure. Herein, we reported the synthesis of ternary Pt@PdRu nanoalloy aerogels with ligand effect of PdRu on Pt-enriched surface through electrochemical cycling. Pt@PdRu aerogels with optimized Pt surface electronic structure exhibited high mass activity and specific activity of Pt@PdRu about 450 mA mgPt -1 and 1.09 mA cm-2, which were 1.4 and 1.6 times than that of commercial Pt/C. Meanwhile, Pt@PdRu aerogels have higher electrochemical stability comparable to commercial Pt/C. In-situ FTIR spectra results proved that the glucose oxidation reaction on Pt@PdRu aerogels followed the CO-free direct pathway reaction mechanism and part of the products are CO2 by completed oxidation. Furthermore, the ADGFC with Pt@PdRu ultrathin anode catalyst layer showed a much higher power density of 6.2 mW cm-2 than commercial Pt/C (3.8 Mw cm-2). To simulate the blood fuel cell, the Pt@PdRu integrated membrane electrode assembly was exposed to glucose solution and a steady-state open circuit of approximately 0.6 V was achieved by optimizing the glucose concentration in cell system.

Structural Regulation of Au-Pt Bimetallic Aerogels for Catalyzing the Glucose Cascade Reaction

Bimetallic nanostructures are promising candidates for the development of enzyme-mimics, yet the deciphering of the structural impact on their catalytic properties poses significant challenges. By leveraging the structural versatility of nanocrystal aerogels, this study reports a precise control of Au-Pt bimetallic structures in three representative structural configurations, including segregated, alloy, and core-shell structures. Benefiting from a synergistic effect, these bimetallic aerogels demonstrate improved peroxidase- and glucose oxidase-like catalytic performances compared to their monometallic counterparts, unleashing tremendous potential in catalyzing the glucose cascade reaction. Notably, the segregated Au-Pt aerogel shows optimal catalytic activity, which is 2.80 and 3.35 times higher than that of the alloy and core-shell variants, respectively. This enhanced activity is attributed to the high-density Au-Pt interface boundaries within the segregated structure, which foster greater substrate affinity and superior catalytic efficiency. This work not only sheds light on the structure-property relationship of bimetallic catalysts but also broadens the application scope of aerogels in biosensing and biological detections.

Strain Effects in Ru-Au Bimetallic Aerogels Boost Electrocatalytic Hydrogen Evolution

To improve the sluggish kinetics of the hydrogen evolution reaction (HER), a key component in water-splitting applications, there is an urgent desire to develop efficient, cost-effective, and stable electrocatalysts. Strain engineering is proving an efficient strategy for increasing the catalytic activity of electrocatalysts. This work presents the development of Ru-Au bimetallic aerogels by a simple one-step in situ reduction-gelation approach, which exhibits strain effects and electron transfer to create a remarkable HER activity and stability in an alkaline environment. The surface strain induced by the bimetallic segregated structure shifts the d-band center downward, enhancing catalysis by balancing the processes of water dissociation, OH* adsorption, and H* adsorption. Specifically, the optimized catalyst shows low overpotentials of only 24.1 mV at a current density of 10 mA cm-2 in alkaline electrolytes, surpassing commercial Pt/C. This study can contribute to the understanding of strain engineering in bimetallic electrocatalysts for HER at the atomic scale.

Structural investigations of Au-Ni aerogels: morphology and element distribution

The physical properties of nanomaterials are determined by their structural features, making accurate structural control indispensable. This carries over to future applications. In the case of metal aerogels, highly porous networks of aggregated metal nanoparticles, such precise tuning is still largely pending. Although recent improvements in controlling synthesis parameters like electrolytes, reductants, or mechanical stirring, the focus has always been on one particular morphology at a time. Meanwhile, complex factors, such as morphology and element distributions, are studied rather sparsely. We demonstrate the capabilities of precise morphology design by deploying Au-Ni, a novel element combination for metal aerogels in itself, as a model system to combine common aerogel morphologies under one system for the first time. Au-Ni aerogels were synthesized via modified one- and two-step gelation, partially combined with galvanic replacement, to obtain aerogels with alloyed, heterostructural (novel metal aerogel structure of interconnected nanoparticles and nanochains), and hollow spherical building blocks. These differences in morphology are directly reflected in the physisorption behavior, linking the isotherm shape and pore size distribution to the structural features of the aerogels, including a broad-ranging specific surface area (35-65 m2 g-1). The aerogels were optimized regarding metal concentration, destabilization, and composition, revealing some delicate structural trends regarding the ligament size and hollow sphere character. Hence, this work significantly improves the structural tailoring of metal aerogels and possible up-scaling. Lastly, preliminary ethanol oxidation tests demonstrated that morphology design extends to the catalytic performance. All in all, this work emphasizes the strengths of morphology design to obtain optimal structures, properties, and (performances) for any material application.