Electrochemical supermolecular templating of mesoporous Rh films

Mesoporous Gold Film with Surface Sulfur Modification to Enable Dendrite-Free Lithium Plating/Stripping for Long-Life Lithium Metal Anodes

The formation of a lithiophilic phase is an effective method to inhibit the growth of lithium dendrites and obtain high-performance Li metal anodes (LMAs). Nonetheless, previous studies have overlooked the underlying mechanistic studies that modulate the structure of the lithiophilic phase as well as lithiophilicity. A self-supporting sulfur-modified mesoporous gold film on nickel foam (SMGF@NF) for LMAs is created with mesoporous structure, which can provide sufficient active sites for uniform lithium deposition. The synergistic promotion of lithiophilic gold and sulfur leads to uniform lithium nucleation and induces consistent lithium removal during lithium stripping. The doping of S promotes the decomposition of bistrifluoromethanesulfonimide lithium salt to generate lithium fluorde, thus forming a more stable solid electrolyte interface. Combining the multifaceted advantages of SMGF@NF, its lithium-plated electrode can achieve ultralong cycle life in symmetrical batteries (over 1000 h at 0.5 mA cm^-2 and 1 mAh cm^-2 ) and ultralow overpotential (≈10 mV). Meanwhile, the Li-SMGF@NF||LiFePO₄ full cell achieves a high cycling performance and rate capability (92.4% capacity retention after 1000 cycles at 5 C). The study probes into the composite electrode surface composition and structure, revealing the mechanism of high-performance LMAs.

Porous Noble Metal Electrocatalysts: Synthesis, Performance, and Development

Active sites (intrinsic activity, quantity, and distribution), electron transfer, and mass diffusion are three important factors affecting the performance of electrocatalysts. Composed of highly active components which are built into various network structures, porous noble metal is an inherently promising electrocatalysts. In recent years, great efforts have been made to explore new efficient synthesis methods and establish structural-performance relationships in the field of porous noble metal electrocatalysis. In this review, the very recent progress in strategies for preparing porous noble metal, including innovation and deeper understanding of traditional methods is summarized. A discussion of relationship between porous noble metal structure and electrocatalytic performance, such as accessibility of active sites, connectivity of skeleton structures, channels dimensions, and hierarchical structures, is provided.

Mesoporous gold-silver alloy films towards amplification-free ultra-sensitive microRNA detection

Herein, we report the preparation of mesoporous gold (Au)-silver (Ag) alloy films through the electrochemical micelle assembly process and their applications as microRNA (miRNA) sensors. Following electrochemical deposition and subsequent removal of the templates, the polymeric micelles can create uniformly sized mesoporous architectures with high surface areas. The resulting mesoporous Au-Ag alloy films show high current densities (electrocatalytic activities) towards the redox reaction between potassium ferrocyanide and potassium ferricyanide. Following magnetic isolation and purification, the target miRNA is adsorbed directly on the mesoporous Au-Ag film. Electrochemical detection is then enabled by differential pulse voltammetry (DPV) using the [Fe(CN)6]3-/4- redox system (the faradaic current for the miRNA-adsorbed Au-Ag film decreases compared to the bare film). The films demonstrate great advantages towards miRNA sensing platforms to enhance the detection limit down to attomolar levels of miR-21 (limit of detection (LOD) = 100 aM, s/n = 3). The developed enzymatic amplification-free miniaturized analytical sensor has promising potential for RNA-based diagnosis of diseases.

Highly Active Hollow RhCu Nanoboxes toward Ethylene Glycol Electrooxidation

The efficient electrocatalysts toward the ethylene glycol oxidation reaction (EGOR) are highly desirable for direct ethylene glycol fuel cells because of the sluggish kinetics of anodic EGOR. Herein, porous RhCu nanoboxes are successfully prepared through facile galvanic replacement reaction and succedent sodium borohydride reduction strategy. Benefiting from hierarchical pore structure, RhCu nanoboxes display excellent electrocatalytic performance toward the EGOR in alkaline medium with a mass activity of 775.1 A g_Rh ^-1 , which is 2.8 times as large as that of commercial Rh nanocrystals. Moreover, the long-term stability of RhCu nanoboxes is better than that of commercial Rh nanocrystals. Furthermore, the theoretical calculations demonstrate that RhCu nanoboxes possess lower adsorption energy of CO and lower reaction barrier (0.27 eV) for the CO_ads oxidation with aid of the adsorbed OH_ads species, resulting in the outstanding electrocatalytic performance toward the EGOR. This work provides a meaningful reference for developing highly effective electrocatalysts toward the EGOR.

Bimetallic mesoporous RhRu film for electrocatalytic nitrogen reduction to ammonia

Bimetallic mesoporous RhRu film on Ni foam has been prepared for the efficient electrosynthesis of ammonia.

Effective electrocatalytic methanol oxidation of Pd-based metallic glass nanofilms

Compared to their conventional polycrystalline Pd counterparts, Pd79Au9Si12 (at%) - metallic glass (MG) nanofilm (NF) electrocatalysts offer better methanol oxidation reaction (MOR) in alkaline medium, CO poisoning tolerance and catalyst stability even at high scan rates or high methanol concentrations owing to their amorphous structure without grain boundaries. This study evaluates the influence of scan rate and methanol concentration by cyclic voltammetry, frequency-dependent electrochemical impedance spectroscopy and a related equivalent circuit model at different potentials in Pd-Au-Si amorphous NFs. Structural and compositional differences for the NFs are assessed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray (EDX) mapping and X-ray diffraction (XRD). The ratio of the forward to reverse peak current density ipf/ipb for the MG NFs is ∼2.2 times higher than for polycrystalline Pd NFs, evidencing better oxidation of methanol to carbon dioxide in the forward scan and less poisoning of the electrocatalysts by carbonaceous (e.g. CO, HCO) species. Moreover, the electrochemical circuit model obtained from EIS measurements reveals that the MOR occurring around -100 mV increases the capacitance without any significant change in oxidation resistance, whereas CO2 formation towards lower potentials results in a sharp increase in the capacitance of the Faradaic MOR at the catalyst interface and a slight decrease in the corresponding resistance. These results, together with the high ipf/ipb = 3.37 yielding the minimum amount of carbonaceous species deposited on the thin film during cyclic voltammetry and stability in the alkaline environment, can potentially make these amorphous thin films potential candidates for fuel-cell applications.

A universal approach for the synthesis of mesoporous gold, palladium and platinum films for applications in electrocatalysis

High-surface-area mesoporous materials expose abundant functional sites for improved performance in applications such as gas storage/separation, catalysis, and sensing. Recently, soft templates composed of amphiphilic surfactants and block copolymers have been used to introduce mesoporosity in various materials, including metals, metal oxides and carbonaceous compounds. In particular, mesoporous metals are attractive in electrocatalysis because their porous networks expose numerous unsaturated atoms on high-index facets that are highly active in catalysis. In this protocol, we describe how to create mesoporous metal films composed of gold, palladium, or platinum using block copolymer micelle templates. The amphiphilic block copolymer micelles are the sacrificial templates and generate uniform structures with tunable pore sizes in electrodeposited metal films. The procedure describes the electrodeposition in detail, including parameters such as micelle diameters, deposition potentials, and deposition times to ensure reproducibility. The micelle diameters can be controlled by swelling the micelles with different solvent mixtures or by using block copolymer micelles with different molecular weights. The deposition potentials and deposition times allow further control of the mesoporous structure and its thickness, respectively. Procedures for example applications are included: glucose oxidation, ethanol oxidation and methanol oxidation reactions. The synthetic methods for preparation of mesoporous metal films will take ~4 h; the subsequent electrochemical tests will take ~5 h for glucose sensing and ~3 h for alcohol oxidation reaction.

Electrochemical Synthesis of Mesoporous Architectured Ru Films Using Supramolecular Templates

The electrochemical synthesis of mesoporous ruthenium (Ru) films using sacrificial self-assembled block polymer micelles templates, and its electrochemical surface oxidation to RuO_x is described. Unlike standard methods such as thermal oxidation, the electrochemical oxidation method described here retains the mesoporous structure. Ru oxide materials serve as high-performance supercapacitor electrodes due to their excellent pseudocapacitive behavior. The mesoporous architectured film shows superior specific capacitance (467 F g^-1_Ru ) versus a nonporous Ru/RuO_x electrode (28 F g^-1_Ru ) that is prepared via the same method but omitting the pore-directing polymer. Ultrahigh surface area materials will play an essential role in increasing the capacitance of this class of energy storage devices because the pseudocapacitive redox reaction occurs on the surface of electrodes.

Self-assembly of block copolymers towards mesoporous materials for energy storage and conversion systems

This paper reviews the progress in the field of block copolymer-templated mesoporous materials, including synthetic methods, morphological and pore size control and their potential applications in energy storage and conversion devices.

Clean rhodium nanoparticles prepared by laser ablation in liquid for high performance electrocatalysis of the hydrogen evolution reaction

Rhodium nanoparticles (NPs) were prepared by a one-step, green and facile procedure consisting in laser ablation of a bulk Rh target immersed in pure water (W-Rh-NPs) or ethanol (E-Rh-NPs). When embedded in mesoporous carbon based inks, both W-Rh-NPs and E-Rh-NPs show excellent activity towards the hydrogen evolution reaction in acidic media, operating close to the thermodynamic potential with 85-97% faradaic yields and low Tafel slopes of 50-54 mV per decade in the low overpotential region (η < 20 mV). A superior activity of W-Rh-NPs with respect to E-Rh-NPs is ascribed to the absence of surface carbon reducible species derived from the synthesis in organic solvent, and thus confirms the importance of the use of water as the preferred medium for laser synthesis of clean nanocrystals in liquid environment. These results provide an important contribution to the impelling need for the preparation of nano-catalysts based on energy critical materials by clean, sustainable and low cost routes.