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Precisely modulating the Ru-O covalency in RuOx for enhanced stability in proton exchange membrane water electrolysis is highly desired. However, transition metals with d-valence electrons, which were doped into or alloyed with RuOx, are inherently susceptible to the influence of coordination environment, making it challenging to modulate the Ru-O covalency in a precise and continuous manner. Here, we first deduce that the introduction of lanthanide with gradually changing electronic configurations can continuously modulate the Ru-O covalency owing to the shielding effect of 5s/5p orbitals. Theoretical calculations confirm that the durability of Ln-RuOx following a volcanic trend as a function of Ru-O covalency. Among various Ln-RuOx, Er-RuOx is identified as the optimal catalyst and possesses a stability 35.5 times higher than that of RuO2. Particularly, the Er-RuOx-based device requires only 1.837 V to reach 3 A cm−2 and shows a long-term stability at 500 mA cm−2 for 100 h with a degradation rate of mere 37 μV h−1. Lack of stability in RuO2-based catalysts at industrial currents impedes their use in green hydrogen production. Here, the authors show that incorporating lanthanide elements into RuOx shields against external factors, enabling fine-tuned Ru-O covalency for durable oxygen evolution reaction electrocatalysis. [ABSTRACT FROM AUTHOR]

The precise structural integration of single-atom and high-entropy-alloy features for energy electrocatalysis is highly appealing for energy conversion, yet remains a grand challenge. Herein, we report a class of single-atom Mo-tailored PdPtNiCuZn high-entropy-alloy nanosheets with dilute Pt-Pt ensembles and intrinsic tensile strain (Mo1-PdPtNiCuZn) as efficient electrocatalysts for enhancing the methanol oxidation reaction catalysis. The as-made Mo1-PdPtNiCuZn delivers an extraordinary mass activity of 24.55 A mgPt−1 and 11.62 A mgPd+Pt−1, along with impressive long-term durability. The planted oxophilic Mo single atoms as promoters modify the electronic structure of isolated Pt sites in the high-entropy-alloy host, suppressing the formation of CO adsorbates and steering the reaction towards the formate pathway. Meanwhile, Mo promoters and tensile strain synergistically optimize the adsorption behaviour of intermediates to achieve a more energetically favourable pathway and minimize the methanol oxidation reaction barrier. This work advances the design of atomically precise catalytic sites by creating a new paradigm of single atom-tailored high-entropy alloys, opening an encouraging pathway to the design of CO-tolerance electrocatalysts. Atomically precise modification of high-entropy alloys is highly appealing for electrocatalysis. Here, the authors design single-atom Mo-tailored high-entropy alloy nanosheets with dilute Pt-Pt ensembles and intrinsic tensile strain for promoting methanol electro-oxidation towards formate. [ABSTRACT FROM AUTHOR]

Palladium (Pd)‐based materials have attracted increasing attentions as a kind of novel candidate catalysts for many electrocatalytic reactions to replace classic platinum (Pt) catalysts, especially in the fuel cell‐related electrocatalysis. However, the requirement of high activity and stability toward further practical applications makes the development of Pd‐based catalysts cease to advance. Combining alloying and structure‐controlled strategies has well addressed this challenge by optimizing the adsorption/desorption behaviors toward reaction intermediates. Herein, the recent advances of rational structural designs in terms of tuning the dimensionalities of Pd‐based nanoalloys are overviewed. To further enhance the intrinsic electrocatalytic activity, several advanced strategies, including intermetallics, doping, defects, surface, and interface engineering, are presented to engineer the electronic and/or physical properties of Pd‐based electrocatalysts. Using typical electrocatalytic reactions as probes, the significance of structural regulation of Pd‐based nanocrystals on the enhanced electrocatalysis is demonstrated. Finally, several possible trends and challenges for future advanced research directions are presented. It is anticipated that the rational structural regulation can make promising Pd‐based catalysts touch the ceiling of electrocatalytic activity and stability. [ABSTRACT FROM AUTHOR]

Ultrathin nanosheet catalysts deliver great potential in catalyzing the oxygen reduction reaction (ORR), but encounter the ceiling of the surface atomic utilizations, thus presenting a challenge associated with further boosting catalytic activity. Herein, a kind of PdPtCu ultrathin nanorings with increased numbers of electrocatalytically active sites is reported, with the purpose of breaking the activity ceiling of conventional catalysts. The as‐made PdPtCu nanorings possess abundant high‐index facets at the edge of both the exterior and interior surfaces. An ultrahigh electrochemical active surface area of 92.2 m2 g–1PGM is achieved on this novel catalyst, much higher than that of the commercial Pt/C catalyst. The optimized Pd39Pt33Cu28/C shows a great enhanced ORR activity with a specific activity of 2.39 mA cm–2 and a mass activity of 1.97 A mg–1PGM at 0.9 V (versus RHE), as well as superior durability within 30 000 cycles. Density function theory calculations reveal that the high‐index facets and alloying Cu atoms can optimize the oxygen adsorption energy, explaining the enhanced ORR activity. Overcoming a key technical barrier in sub‐nanometer electrocatalysts, this work successfully introduces the hollow structures into the ultrathin nanosheets, heralding the exciting prospects of high‐performance ORR catalysts in fuel cells. [ABSTRACT FROM AUTHOR]

Core/shell nanocatalysts are a class of promising materials, which achieve the enhanced catalytic activities through the synergy between ligand effect and strain effect. However, it has been challenging to disentangle the contributions from the two effects, which hinders the rational design of superior core/shell nanocatalysts. Herein, we report precise synthesis of PdCu/Ir core/shell nanocrystals, which can significantly boost oxygen evolution reaction (OER) via the exclusive strain effect. The heteroepitaxial coating of four Ir atomic layers onto PdCu nanoparticle gives a relatively thick Ir shell eliminating the ligand effect, but creates a compressive strain of ca. 3.60%. The strained PdCu/Ir catalysts can deliver a low OER overpotential and a high mass activity. Density functional theory (DFT) calculations reveal that the compressive strain in Ir shell downshifts the d‐band center and weakens the binding of the intermediates, causing the enhanced OER activity. The compressive strain also boosts hydrogen evolution reaction (HER) activity and the strained nanocrystals can be served as excellent catalysts for both anode and cathode in overall water‐splitting electrocatalysis. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a pivotal element of electrochemical water splitting which is able to produce clean hydrogen as an alternative to fossil fuel. Developing efficient Pt‐based electrocatalysts for the HER to work at all pHs is highly desirable, however, still a significant challenge, especially in alkaline conditions due to sluggish water dissociation and OHad transfer. Here, a new strategy for making a class of amorphous WOx‐surface decorated PtNi@Pt dendritic nanowires (WOx‐PtNi@Pt DNWs) to achieve highly efficient pH‐universal HER electrocatalysis is reported. The as‐made WOx‐PtNi@Pt DNWs display superior HER performance with the overpotentials of 24, 5, and 22 mV in 0.1 m KOH, 0.1 m HClO4, and 0.5 m phosphate‐buffered saline, respectively, at a current density of 10 mA cm−2. The mass activity of WOx‐PtNi@Pt DNWs in alkaline conditions is 3.3 mA μgPt−1 at an overpotential of 70 mV, among the best in all the reported materials. Theoretical calculations confirm the introduction of WOx to the PtNi DNWs plays a pivotal role in promoting the efficient electron transfer for the alkaline and acidic HER. The activation of the PtNi region within the PtNiWO interface is achieved by the WOx induced strain effect, which guarantees the superior performance in the HER. [ABSTRACT FROM AUTHOR]

Hydrogen production through proton exchange membrane water electrolyzers (PEMWE) requires more active and stable electrocatalysts in acidic media. Herein, a class of Ir‐based alloys is reported with flower‐like structure as excellent electrocatalysts both for hydrogen and oxygen generation in acid. Specially, the IrNi alloy nanoflowers (IrNi NFs) present the best hydrogen evolution reaction (HER) performance, revealed by a low Tafel slope and overpotential at current density of 10 mA cm−2, exceeding the commercial Pt/C. It is discovered that alloying Ir with Ni can decrease the hydrogen binding energy (HBE) of Ir metal, resulting in almost 2.5 times increase in the HER intrinsic activity of IrNi NFs than Ir NFs. The IrNi NFs catalyst is also highly efficient in oxygen evolution reaction with mass activity of 379 A g−1 Ir at 1.51 V versus reversible hydrogen electrode. Furthermore, the overall water‐splitting devices using the IrNi NFs as catalysts for both cathode and anode show a low cell voltage of 1.60 V at 10 mA cm−2 and long‐term stability within 1000 cycles. This work uncovers that HBE optimization is the key of enhancing HER activity on Ir‐based alloys and these Ir‐based NFs hold great promise in future application in the PEMWE. [ABSTRACT FROM AUTHOR]

Metal‐organic frameworks (MOFs) and MOF‐derived materials have attracted great attention as alternatives to noble‐metal based electrocatalysts owing to their intriguing structure properties, especially for high efficiency and stable oxygen reduction reaction (ORR). Herein, we employed a one‐pot reaction to make a multimetal (Fe, Co, Cu, and Zn) mixed zeolitic imidazolate framework (MM‐ZIF) via adopting a simple in situ redox reaction. Further pyrolysis of the target MM‐ZIF, a highly porous carbon polyhedron (FC‐C@NC) grafted with abundant carbon nanotubes was obtained, in which ultrasmall Co nanoparticles with partial lattice sites substituted by Fe and Cu were embedded. The obtained FC‐C@NC possessed large surface area, highly porous structure, widely‐spread metal active sites, and conductive carbon frameworks, contributing to outstanding ORR activity and long‐term stability. It displayed superior tolerance to methanol crossover and exceeded the commercial Pt/C catalyst and most previously reported non‐noble‐metal catalysts. Impressively, the as‐produced FC‐C@NC‐based zinc‐air battery afforded an open‐circuit potential of 1.466 V, a large specific capacity of 659.5 mAh/g, and a high gravimetric energy density of 784.3 Wh/kgZn, significantly outperforming the Pt/C‐based cathode. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting plays a crucial role in the development of clean and renewable energy production and conversion, which is a promising pathway to reduce social dependence on fossil fuels. Thus, highly active, cost‐efficient, and robust catalysts must be developed to reduce the reaction overpotential and increase electrocatalytic efficiency. In this review, recent research efforts toward developing advanced electrocatalysts based on noble metals with outstanding performance for water splitting catalysis, which is mainly dependent on their structure engineering, are summarized. First, a simple description of the water‐splitting mechanism and some promising structure engineering strategies are given, including heteroatom incorporation, strain engineering, interface/hybrid engineering, and single atomic construction. Then, the underlying relationship between noble metal electronic/geometric structure and performance for water splitting is discussed with the assistance of theoretical simulation. Finally, a personal perspective is provided in order to highlight the challenges and opportunities for developing novel electrocatalysts suitable for a wide range of commercial uses in water splitting for structural engineering applications. [ABSTRACT FROM AUTHOR]

Electrocatalysis plays a crucial role in the transformation between electrical and chemical energy. Particularly, the search for high-performance electrocatalysts lies at the heart of numerous renewable energy conversion and storage technologies, such as water electrolysers and fuel cells, which potentially enable an energy-sustainable society. This Frontier article briefly describes the pathway from debates on "animal electricity" to the current understanding of electrocatalysis, and how knowledge can be harnessed to guide the discovery of well-defined electrocatalysts based on precious metal nanocrystals. We summarize basic design principles and key parameters associated with a good electrocatalyst and highlight the adoption of wet-chemical approaches for constructing nanocatalysts with desired structural properties. We close this article with personal perspectives on current challenges and future research directions in this field. [ABSTRACT FROM AUTHOR]

The strain effect, along with the ligand effect and synergistic effect, contributes primarily to the optimization of electrocatalytic activity and stability. The strain effect leads to a shift in the d-band center and alters binding energies toward adsorbates. Under electrocatalytic circumstances, the strain effect and ligand effect by and large function in combination; however, the decay and vanishing of the ligand effect precede the strain effect as the thickness of the shell in the core/shell structure or metallic overlayers on substrates increases. The strain effect on electrocatalytic activity can be well engineered by tuning the thickness of shells or atomic composition. Microstrain, or localized lattice strain, is another type of strain associated with structural defects such as grain boundaries and multi-twinning. In this review, we discuss the origin of the strain effect and how it affects electrocatalytic activity based on the d-band model. We present the structural characterization and quantitative determination of strain. Metal-based nanocrystals are basically grouped into two types of structures to which the strain engineering applies, i.e. lattice strain-associated structures (which include the general core/shell structure and solid solution alloy) and multiple defects-induced structures. Then analysis is performed on the correlation of strain and ligand effects and on the tuning strategies of the strain effect for electrocatalysis. After that, we use representative examples to demonstrate how strain engineering assists in typical electrocatalytic reactions on anodes and cathodes. Finally, we summarize and propose potential research areas in terms of enhancing electrocatalytic activities by strain engineering in the future. [ABSTRACT FROM AUTHOR]

Performance-enhancing strategies of porous carbons include heteroatom(s)-doping and hybridization with other metal-free compounds or metals (such as metal nanoparticles and atomically dispersed metal species). Prof. Amal details the active sites in metal-based catalysts, metal-carbon catalysts and carbon-based catalysts for heterogeneous electrocatalysis of CO SB 2 sb reduction reaction. The active sites in metal-based catalysts, for instance, are situated in crystallographic facets selective toward CO SB 2 sb reduction, interfacial sites due to I in-situ i reduction of metal oxide catalysts, and surface defects. [Extracted from the article]

Abstract: The development of high‐performance oxygen reduction reaction (ORR) catalysts derived from non‐Pt group metals (non‐PGMs) is urgent for the wide applications of proton exchange membrane fuel cells (PEMFCs). In this work, a facile and cost‐efficient supramolecular route is developed for making non‐PGM ORR catalyst with atomically dispersed Fe‐Nx/C sites through pyrolyzing the metal‐organic polymer coordinative hydrogel formed between Fe3+ and α‐L‐guluronate blocks of sodium alginate (SA). High‐angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) and X‐ray absorption spectroscopy (XAS) verify that Fe atoms achieve atomic‐level dispersion on the obtained SA‐Fe‐N nanosheets and a possible fourfold coordination with N atoms. The best‐performing SA‐Fe‐N catalyst exhibits excellent ORR activity with half‐wave potential (E1/2) of 0.812 and 0.910 V versus the reversible hydrogen electrode (RHE) in 0.5 m H2SO4 and 0.1 m KOH, respectively, along with respectable durability. Such performance surpasses that of most reported non‐PGM ORR catalysts. Density functional theory calculations suggest that the relieved passivation effect of OH* on Fe‐N4/C structure leads to its superior ORR activity to Pt/C in alkaline solution. The work demonstrates a novel strategy for developing high‐performance non‐PGM ORR electrocatalysts with atomically dispersed and stable M‐Nx coordination sites in both acidic and alkaline media. [ABSTRACT FROM AUTHOR]

Proton adsorption on metallic catalysts is a prerequisite for efficient hydrogen evolution reaction (HER). However, tuning proton adsorption without perturbing metallicity remains a challenge. A Schottky catalyst based on metal-semiconductor junction principles is presented. With metallic MoB, the introduction of n-type semiconductive g-C3N4 induces a vigorous charge transfer across the MoB/g-C3N4 Schottky junction, and increases the local electron density in MoB surface, confirmed by multiple spectroscopic techniques. This Schottky catalyst exhibits a superior HER activity with a low Tafel slope of 46 mV dec−1 and a high exchange current density of 17 μA cm−2, which is far better than that of pristine MoB. First-principle calculations reveal that the Schottky contact dramatically lowers the kinetic barriers of both proton adsorption and reduction coordinates, therefore benefiting surface hydrogen generation. [ABSTRACT FROM AUTHOR]

Integration of 1D, core/shell, and jagged features into one entity may provide a promising avenue for further enhancing catalyst performance. However, designing such unique nanostructures is extremely challenging. Herein, 1D serrated Au/Pd core/shell nanowires (CSNWs) with jagged edges were produced simply by a one-pot, dual-capping-agent-assisted method involving co-reduction, galvanic replacement, directional coalescence of preformed nanoparticles, and site-selective epitaxial growth of Pd. Au/PdCSNWs, compared with the commercially available Pd/C, exhibited enhanced electrocatalytic performance towards liquid fuel oxidation because of the synergistic effect of the electronic structure and low-coordinated jagged edges. [ABSTRACT FROM AUTHOR]

Ordered intermetallic alloys have attracted extensive attention as advanced electrocatalysts for polymer electrolyte membrane fuel cells (PEMFCs) reactions with much improved activity and stability. Here, latest progress in tuning intermetallic Pt- and Pd-based nanocrystals with tunable morphology and structure for catalyzing both the cathodic reduction of oxygen and anodic oxidation of fuels (e.g., methanol, ethanol and formic acid) in PEMFCs is highlighted. Making/tuning interesting intermetallic PtM (M = Fe, Co, Pb, Cu, etc.)-based nanocrystals for boosting oxygen reduction reaction with high activity and stability by using/controlling high-temperature annealing treatment is discussed. In all the reported Pt-based intermetallic nanocrystals, controlling the degree of ordering under the proper high temperature treatment is the key for achieving the optimized electrocatalysis. In order to search for cheaper catalysts, the progress on making Pd-based intermetallic nanocrystals is also discussed. Furthermore, future research directions are proposed and discussed to further enhance the efficiency of such unique intermetallic multimetallic nanocatalysts. This report aims to demonstrate the potential of ordered intermetallic strategy for boosting electrocatalysis and stimulating more research efforts in this field. [ABSTRACT FROM AUTHOR]

Trimetallic oxyhydroxides are one of the most effective materials for oxygen evolution reaction (OER) catalysis, a key process for water splitting. Herein, we describe a facile wet-chemical method to directly grow a series of coralloid trimetallic oxyhydroxides on arbitrary substrates such as nickel foam (NF) and carbon nanotubes (CNTs). The amount of iron in these oxyhydroxide sponges on NF and CNTs was precisely controlled, revealing that the electrocatalytic activity of the WCoFe trimetallic oxyhydroxides depends on the Fe amount in a volcano-like fashion. The optimized W0.5Co0.4Fe0.1/NF catalyst exhibited an overpotential of only 310 mV to deliver a large current density of 100 mA cm−2 and a very low Tafel slope of 32 mV dec−1. It also showed superior stability with negligible activity decay after use in the OER for 21 days (>500 h). X-ray photoelectron spectroscopy revealed that the addition of Fe leads to an on average lower Co oxidation state, which contributes to the enhanced OER performance. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) cubic superstructures of PtPd nanocubes were achieved by spontaneous adjustment of PtIV reduction kinetics, and exhibited enhanced catalytic activity and long-term durability towards methanol oxidation compared with the state-of-the-art Pt/C. This work demonstrates the first example of designing 3D shaped architectures of PtPd nanocubes for methanol electrooxidation. [ABSTRACT FROM AUTHOR]

The rapid development of nanoscience and nanotechnology provides new opportunities for the sustainable progress of nanoscale catalysts (i.e., nanocatalysts). The introduction of nanocatalysts into electronic devices implants their novel functions into electronic sensing systems, resulting in the testing of many advanced electrochemical sensors and the fabrication of some highly sensitive, selective, and stable sensing platforms. In this Review, we will summarize recent significant progress on exploring advanced carbon nanomaterials (such as carbon nanotubes, graphene, highly ordered mesoporous carbons, and electron cyclotron resonance sputtered nanocarbon film) as nanoscale electrocatalysts (i.e., nanoelectrocatalysts) for constructing the catalytic nanointerfaces of electronic devices to achieve high-sensitivity and high-selectivity electrochemical sensors. Furthermore, different mechanisms for the extraordinary and unique electrocatalytic activities of these carbon nanomaterials will be also highlighted, compared and discussed. An outlook on the future trends and developments in this area will be provided at the end. Notably, to elaborate the nature of carbon nanomaterial, we will mainly focus on the electrocatalysis of single kind of carbon materials rather than their hybrid composite materials. We expect that advanced carbon nanomaterials with unique electrocatalytic activities will continue to attract increasing research interest and lead to new opportunities in various fields of research. [ABSTRACT FROM AUTHOR]

Herein, a novel tunable electrocatalytic nanobiointerface for the construction of a high-sensitivity and high-selectivity biofuel-cell (BFC)-based self-powered biosensor for the detection of transcription factor protein p53 is reported, in which bilirubin oxidase (BOD)/DNA supramolecular modified graphene/platinum nanoparticles hybrid nanosheet (GPNHN) works as a new enhanced material of biocathode to control the attachment of target, and thus tune the electron-transfer process of oxygen reduction for transducing signaling magnification. It is found that in the presence of p53, the strong interaction between the wild-type p53 and its consensus DNA sequence on the electrode surface can block the electron transfer from the BOD to the electrode, thus providing a good opportunity for reducing the electrocatalytic activity of oxygen reduction in the biocathode. This in combination with the glucose oxidation at the carbon nanotube/Meldola's blue/glucose dehydrogenase bioanode can result in a current/or power decrease of BFC in the presence of wild-type p53. The specially designed BFC-based self-powered p53 sensor shows a wide linear range from 1 p M to 1 μ M with a detection limit of 1 p M for analyzing wild-type p53. Most importantly, our BFC-based self-powered sensors can detect the concentrations of wild-type p53 in normal and cancer cell lysates without any extensive sample pretreatment/separation or specialized instruments. The present BFC-based self-powered sensor can provide a simple, economical, sensitive, and rapid way for analyzing p53 protein in normal and cancer cells at clinical level, which shows great potential for creating the treatment modalities that capitalize on the concentration variation of the wild-type p53. [ABSTRACT FROM AUTHOR]

Pt-based nanostructures serving as anode catalysts for the methanol oxidation reaction (MOR) have been widely studied for many years. Nevertheless, challenging issues such as poor reaction kinetics and the short-term stability of the MOR are the main drawbacks of such catalysts and limit their applications. Herein, we have developed a facile approach to encapsulate Pt nanoparticles (NPs) inside the nanochannels of porous carbon nanotubes (CNTs; Pt-in-CNTs) as a new enhanced electrocatalytic material. The as-prepared CNTs offer simultaneously ordered diffusion channels for ions and a confinement effect for the NPs, which both facilitate the promotion of catalytic kinetics and avoid the Ostwald ripening of Pt NPs, thus leading to high activity and durable cycle life as an anode catalyst for MOR. This work provides a new approach for enhancing the stability and activity by optimizing the structure of the catalyst, and the Pt-in-CNTs represent the most durable catalysts ever reported for MOR. [ABSTRACT FROM AUTHOR]

Dumbbell-like PtxPd100–x–Fe3O4 nanoparticles (NPs) were synthesized and studied for electrocatalytic reduction and sensing of H2O2. In 0.1 M phosphate buffered saline (PBS) solution, the 4–10 nm PtxPd100–x–Fe3O4 NPs showed the Pt/Pd composition-dependent catalysis with Pt48Pd52–Fe3O4 NPs having the best activity. The Pt48Pd52–Fe3O4 NPs were tested for H2O2 detection, and their H2O2 detection limit reached 5 nM, which was suitable for monitoring H2O2 generated from Raw 264.7 cells. These dumbbell-like PtPd–Fe3O4 NPs are the most sensitive probe ever reported and can be used to achieve real-time quantitative detection of H2O2 in biological environment for biological and biomedical applications. [ABSTRACT FROM AUTHOR]

Summary: Nobel metal nanomaterials (NMNs) with interesting physical and chemical properties are ideal building blocks for engineering and tailoring nanoscale structures for specific technological applications. Particularly, effectively controlling the size, shape, architecture, composition, hybrid and microstructure of NMNs plays an important role on revealing their new or enhanced functions and application potentials such as fuel cell and analytical sensors. This review article focuses on recent advances on controllable synthesis and fuel cell and sensing applications of NMNs. First, recent contributions on developing a wet-chemical approach for the controllable synthesis of noble metal nanomaterials with a rich variety of shapes, e.g. single-component Pt, Pd, Ag and Au nanomaterials, multi-component core/shell, intermetallic or alloyed nanomaterials, metal fluorescent nanoclusters and metal nanoparticles-based hybrid nanomaterials, are summarized. Then diversified approaches to different types of NMNs-based nanoelectrocatalysts with the aim to enhance their activity and durability for fuel cell reactions are outlined. The review next introduces some exciting push in the use of NMNs as enhanced materials or reporters or labels for developing new analytical sensors including electrochemical, colorimetric and fluorescent sensors. Finally, we conclude with a look at the future challenges and prospects of the development of NMNs. [ABSTRACT FROM AUTHOR]

Abstract: Nanomaterial modified electrode is useful for catalytic, analytical and biotechnological applications. Herein, a simple and sensitive method for the electrocatalytic detection of ascorbic acid (AA) using ultrathin Pd nanowire (NW) modified glassy carbon electrode is presented. Electrochemical data reveal that Pd NWs can effectively enhance the electron transfer between AA and electrode, and thus reduce the overpotential of AA oxidation. Particularly, the current–time curve shows that the catalytic oxidation current is linearly dependent on AA concentration in the range of 25μM–0.9mM with a correlation coefficient 0.9998, and a detection limit of 0.2μM (S/N=3) is obtained with an excellent reproducibility. What is more, the present Pd NWs-based electrochemical sensing platform can successfully be used as enhanced element for the detection of AA in the practical samples such as human serum and vitamin C beverage with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract: Morphological control of nanomaterials is of great interest due to their size and shape-dependent chemical and physical properties and very important applications in many fields such as biomedicine, sensors, electronics and others. In this paper, we reported a simple strategy for synthesizing gold nanowire assembling architecture at room temperature. It is found that two important factors, the proper volume ratio of ethanol to water and poly(vinyl pyrrolidone) (PVP), will play important roles in synthesizing flower-like short gold nanowire assembling spheres. Furthermore, the obtained flower-like gold assembling spheres with high surface-to-volume ratio have been employed as enhancing materials for electrochemical sensing H2O2. The present electrochemical sensing platform exhibited good electrocatalytic activity towards the reduction of H2O2. The detection limit for H2O2 was found to be 1.2μM, which was lower than certain enzyme-based biosensors. [Copyright &y& Elsevier]

Abstract: A promising method for assembling carbon nanotubes (CNTs) and poly(diallyldimethylammonium chloride) protected Prussian blue nanoparticles (P-PB) to form three-dimensional (3D) nanostructured films is proposed. The electrostatic interaction, combined with layer-by-layer self-assembly (LBL), between negatively charged CNTs and positively charged P-PB is strong enough to drive the formation of the 3D nanostructured films. Thus, prepared multilayer films were characterized by ultraviolet–visible–near-infrared spectroscopy (UV–vis–NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). Regular growth of the mutilayer films is monitored by UV–vis–NIR and CV. SEM provides the morphology of the multilayer films. The 3D multilayer films exhibit good electrocatalytic activity for the reduction of H2O2. This is a very general and powerful technique for the assembling 3D nanostructured films containing carbon nanotubes and nanoparticles. This assembling method introduces opportunities for the incorporation of various functionalities into nanotube devices, which, in turn, opens up the possibility of building more complex multicomponent nanostructures with potential application, such as biosensing devices. [Copyright &y& Elsevier]

Abstract: This review covers recent advances in synthesis and electrochemical applications of gold nanoparticles (AuNPs). Described approaches include the synthesis of AuNPs via designing and choosing new protecting ligands; and applications in electrochemistry of AuNPs including AuNPs-based bioelectrochemical sensors, such as direct electrochemistry of redox-proteins, genosensors and immunosensors, and AuNPs as enhancing platform for electrocatalysis and electrochemical sensors. [Copyright &y& Elsevier]

An introduction is presented in which the editor discusses articles in the issue on topics including solar cells, electrocatalysis, batteries, and supercapacitors.

• 1D and 2D noble metal-based nanocrystals with various nanostructures are summarized. • Typical strategies for tuning the nanostructures of 1D and 2D noble metal-based nanocrystals are discussed. • The underlying mechanisms behind the structure-performance relationship are discussed. • Present challenges and perspectives to the research of 1D and 2D noble metal-based nanocrystals are provided. Recently, one- (1D) and two-dimensional (2D) noble metal-based nanocrystals have triggered tremendous interest due to their unique anisotropic structure in the field of electrochemical energy conversion. In this review, we summarize the latest research developments in 1D and 2D noble metal-based nanocrystals with various nanostructures, and their potential applications as electrocatalysts toward fuel-cell-related electrocatalysis. Five strategies including size, shape, composition, surface, and interface engineering are proposed to rationally design the nanoarchitectures of the 1D and 2D noble metal-based electrocatalysts. In addition, we also highlight the underlying mechanisms behind the structure-property relationship. Finally, we conclude the current challenges and give our perspectives on the development of high-performance 1D and 2D noble metal-based electrocatalysts. We hope this review could offer timely information on the research of 1D and 2D noble metal-based nanocrystals and provide guidance for regulating their electrocatalytic properties. [ABSTRACT FROM AUTHOR]

Industrializing water electrolyzers demands better electrocatalysts, especially for the anodic oxygen evolution reaction (OER). The prevailing OER catalysts are Ir or Ru‐based nanomaterials, however, they still suffer from insufficient stability. An alternative yet considerably less explored approach is to upgrade Rh, a known stable but moderately active element for OER electrocatalysis, via rational structural engineering. Herein, a precise synthesis of assembled RhRuFe trimetallenes (RhRuFe TMs) with an average thickness of 1 nm for boosting overall water splitting catalysis is reported. Favorable mass transport and optimized electronic structure collectively render RhRuFe TMs with an improved OER activity of an overpotential of 330 mV to deliver 10 mA cm−2, which is significantly lower than the Rh/C control (by 601 mV) and reported Rh‐based OER electrocatalysts. In particular, the RhRuFe TMs‐based water splitting devices can achieve the current density of 10 mA cm−2 at a low voltage of 1.63 V, which is among the best in the Rh‐based bifunctional catalysts for electrolyzers. The addition of Fe in RhRuFe TMs can modulate the strain/electron distribution of the multi‐alloy, which regulates the binding energies of H* and OH* in hydrogen and oxygen evolution reactions for achieving the enhanced bifunctional OER and HER catalysis is further demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Monodisperse, submicrometer-scale platinum (Pt) colloidal spheres were prepared through a simple direct chemical reduction of p-phenylenediamine (PPD)-chloroplatinic acid (H2PtCl6) coordination polymer colloids. It was found that the prepared Pt colloids had the similar size and morphology with their coordination polymer precursors, and the prepared Pt colloids with rough surfaces were three-dimensional (3D) structured assemblies of high-density small Pt nanoparticles. The electrochemical experiments confirmed that the prepared Pt colloids possessed a high electrocatalytic activity towards mainly four-electron reduction of dioxygen to water, making the prepared Pt colloids potential candidates for the efficient cathode material in fuel cells. [Copyright &y& Elsevier]

The performance of fuel-cell related electrocatalysis is highly dependent on the morphology, size and composition of a given catalyst. In terms of rational design of Pt-based catalyst, one-dimensional (1D) ultrafine Pt alloy nanowires (NWs) are considered as a commendable model for enhanced catalysis on account of their favorable mass/charge transfer and structural durability. However, in order to achieve the noble metal catalysts in higher efficiency and lower cost, building high-index facets and shaping hollow interiors should be integrated into 1D Pt alloy NWs, which has rarely been done so far. Here, we report the first synthesis of a class of spiny Pd/PtFe core/shell nanotubes (SPCNTs) constructed by cultivating PtFe alloy branches with rich high-index facets along the 1D removable Pd supports, which is driven by the galvanic dissolution of Pd substrates concomitant with Stranski-Krastanov (S-K) growth of Pt and Fe, for achieving highly efficient fuel-cells-related electrocatalysis. This new catalyst can even deliver electrochemical active surface area (ECSA) of 62.7 m2 g Pt −1, comparable to that of commercial carbon-supported Pt nanoparticles. With respect to oxygen reduction catalysis, the SPCNTs showcase the remarkable mass and specific activity of 2.71 A mg−1 and 4.32 mA cm−2, 15.9 and 16.0 times higher than those of commercial Pt/C, respectively. Also, the catalysts exhibit extraordinary resistance to the activity decay and structural degradation during 50,000 potential cycles. Moreover, the SPCNTs serve as a category of efficient and stable catalysts towards anodic alcohol oxidation. [ABSTRACT FROM AUTHOR]

Pt-based 3D nanodendrites hold great promise as electrocatalysts for renewable energy technologies, yet encounter challenges associated with their structural fragility. This works addresses this challenge by constructing nanodendrites composed of thermally- and electrochemically-stable nanoplates, which enable the breakthrough of both activity and stability of dendrites-type electrocatalysts. Highly-branched dendritic Pt-based nanocrystals possess great potential in catalyzing the oxygen reduction reaction (ORR), but encounter performance ceiling due to their poor thermal and electrochemical stability. Here, we present a novel PtFe nanodendrites (NDs) branched with two-dimensional (2D) twinned nanoplates rather than conventional 1D nanowires, which breaks the ORR performance ceiling of dendritic catalysts by inducing the unique Pt-skin configuration via rationally thermal treatment. By further hybridizing the Pt-skin PtFe NDs/C with amino-functionalized ionic liquids (ILs), we achieve an unprecedented mass activity of 3.15 A/mg Pt at 0.9 V versus reversible hydrogen electrode (RHE) in the PtFe-based ORR electrocatalytic system. They also show excellent electrocatalytic durability for ORR with negligible activity decay and no apparent structural change after 20,000 cycles, in sharp contrast to the nanowires branched PtFe NDs counterpart. The remarkable catalytic performance is attributed to a combination of several structural features, including 2D morphology, twin boundary, partially ordered phase and strong coordination with amino group. This work highlights the significance of stabilizing electrocatalytic structures via morphology tuning, which thus enables further surface and interface modification for performance breakthrough in ORR electrocatalysis. [ABSTRACT FROM AUTHOR]

Highlights • Sensitive fluorescent DNA sensing platform based on ultrathin Ti 3 C 2 was established. • The method combines DNA hybridization with signal amplification of Exo III. • The approach is a simple, rapid and homogeneous mix-and-detect assay. • The sensors was successfully employed to detect PCR-amplified HPV-18 DNA extracted from cervical scrapes samples. Abstract MXenes as a new class of 2D materials have recently been widely applied in energy storage, electrocatalysis, sensors, adsorption, water purification, and so on, due to their tunable versatile properties. Herein, we demonstrate a simple, rapid and highly-sensitive sensing platform based on ultrathin two-dimensional MXene Ti 3 C 2 nanosheets (Ti 3 C 2 NSs) for selective analysis of Human papillomavirus (HPV), a major human pathogens and causative agents of cervical cancer. Ultrathin Ti 3 C 2 NSs, obtained by exfoliating their layered HF-etched powder, exhibit high fluorescence quenching ability to dye-labeled single-stranded DNA (ssDNA) and different affinities for ssDNA and double-stranded DNA (dsDNA). Under the fluorescence quenching effect of Ti 3 C 2 NSs, ssDNA probe (P) shows the minimal fluorescent emission. After the formation of duplex structure with its complementary target, ssDNA (T), the fluorescence intensity enhances evidently. Exonuclease III (Exo III) was used to improve the sensitivity by promoting more fluorescence enhancement. This magnified fluorescent sensor for HPV-18 detection shows a low detection limit of 100 pM and a high specificity. Furthermore, the developed DNA sensor can be employed to determine PCR amplified HPV-18 from cervical scrapes samples. It highlights ultrathin Ti 3 C 2 NSs as a potential candidate for construction of fluorescence DNA biosensors with excellent performances. [ABSTRACT FROM AUTHOR]

Graphical abstract Outstanding heterogeneous catalysis performance could be achieved by rationally engineering the surfaces, architectures, and interfaces of ultrathin two-dimensional metallic nanocrystals, offering great promises in the renewable energy innovations. Abstract Even since the discovery of exfoliated graphene, exponentially growing efforts have been devoted to the search of novel 2 dimensional (2D) nanomaterials with atomic thickness and the extension of their applications. Among the huge 2D materials family, ultrathin 2D metallic nanocrystals gain vast attention due to the unique importance of transition metals to heterogeneous catalysis. Here, we review recent representative advances in ultrathin 2D metallic nanocrystals and their catalytic applications toward a variety of reactions, including the hydrogen generation, oxygen reduction/evolution, CO 2 activation, and small molecules' oxidation/hydrogenation. Special focuses are placed in current understanding of bottom-up fabrication of ultrathin 2D metallic nanocrystals, the establishment of their structure–performance relationship as well as the implication of their real applications in devices. We also shed light on further structural modification of the ultrathin 2D metallic nanocrystals to achieve the optimized catalytic performance. At end of this review, we discuss the remaining challenges and future opportunities in this burgeoning research area. [ABSTRACT FROM AUTHOR]

Abstract: Since the discovery of graphene in 2004, research on 2D materials has grown rapidly. Compared to their bulk counterparts, 2D atomically thin, layered transition‐metal dichalcogenides (TMDCs or MX2) nanosheets exhibit excellent electronic and optical properties, outstanding mechanical flexibility, and exceptional catalytic performance. As a representative of 2D materials, MX2 holds great promise in many potential applications, especially in energy‐related applications. Here, a brief overview of atomically thin layered MX2 nanosheets applied in energy storage and conversion systems is presented. Firstly, the crystal structures and phases, morphologies, and synthesis methods of MX2 are discussed. Sequentially, the achieved progress on atomically thin MX2 in energy‐related applications (i.e., the hydrogen‐evolution reaction, oxygen‐evolution reaction, CO2 electrochemical reduction, electrochemical capacitors, lithium‐ion batteries, sodium‐ion batteries, and lithium–sulfur batteries) is systematically discussed. Finally, the conclusions and some prospects regarding atomically thin MX2 for applications in the field of energy‐storage systems are provided. [ABSTRACT FROM AUTHOR]

Review: recent developments of carbon-based noble-metal-free high-efficiency oxygen reduction electrocatalysts, including heteroatom-doped, transition metal-based nanoparticles, and especially iron carbide (Fe3C)-based carbon nanomaterial composites; 295 refs. [ABSTRACT FROM AUTHOR]

Abstract: Single-walled carbon nanohorns (SWNHs), a new type of carbon nanomaterials, possess excellent catalytic properties, high-purity, and low toxicities, which make them suitable for bioelectrochemical application. Here a biofuel cell anode has been developed by using SWNHs as the support for redox mediator and biocatalyst for the first time. Cyclic voltammetric results show SWNHs promotes the electropolymerization of methylene blue (MB) and the resulted nanocomposite (poly MB–SWNHs) exhibits prominent catalytic ability to the oxidation of nicotinamide adenine dinucleotide. Glucose dehydrogenase was then immobilized on the poly MB–SWNHs modified electrode for the oxidation of glucose. Employing Pt nanoparticles supported on functionalized TiO2 colloidal spheres with nanoporous surface as cathode catalyst, the as-assembled glucose/O2 biofuel cell operate at the physiological condition with good performance. [Copyright &y& Elsevier]

A correction for the article "Monodisperse Au Nanoparticles for Selective Electrocatalytic Reduction of CO2 to CO" that was published in the previous issue is presented.