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The oxygen evolution reaction (OER) is of prime importance in the development of highly efficient electrochemical energy conversion and storage technologies such as water splitting and zinc air batteries. Ru-based nanocatalysts are still the best catalytic system for the OER; however, one of the greatest challenges is their relatively poor stability for the OER. Here, we report a novel architecture of ultrathin RuRh@(RuRh)O2 core/shell nanosheets with a core of ultrathin metallic RuRh nanosheets and a shell of RuO2/RhO2 oxides as superb electrocatalysts toward the OER. The RuRh@(RuRh)O2 core/shell nanosheets can achieve a high electrocatalytic activity toward the OER, with a low 245 mV overpotential at 10 mA cm−2 and a Tafel slope of 51.2 mV dec−1, better than most state-of-the-art Ru-based or Ir-based electrocatalysts for the OER. Moreover, the RuO2/RhO2 oxides shell protect the normally labile RuRh NSs core against dissolution during the OER process, revealed by detailed rotating ring disk electrode (RRDE) measurements for simultaneously recording the dissolution of Ru on the ring electrode and the ex situ measurement of Ru dissolution using the galvanostatic method. Therefore, the RuRh@(RuRh)O2 core/shell nanosheets exhibit much better OER stability in acid media compared with RuRh nanosheets and commercial RuO2. Theoretical calculations reveal that once the formation of the surface oxidation layers is achieved, the O-sites evidentially crossover the Fermi level which could guarantee the high electroactivity towards adsorbates while the RuRh core serves as an electron reservoir with high electrical conductivity. The synergistic effect between the core and shell structure leads to the superior OER performance. [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]

Core–shell architecture coupled with rational surface engineering constitutes an efficient strategy for promoting electrocatalysis on multimetallic nanocrystals via the optimization of composition, facets and coordination environment. Here, by leveraging controlled surface segregation, we realize core–shell formation with systematic tuning of surface composition on well-defined PdCuRu nanocrystals. When applied for the hydrogen evolution reaction (HER), we established a direct correlation between surface composition and activity. In particular, PdCuRu catalysts with a Pd-rich surface achieved an overpotential of 31 mV at a current density of 10 mA cm−2 and a low Tafel slope of 52 mV dec−1 in an alkaline electrolyte, considerably enhanced relative to control PdCuRu/C catalysts with other surface compositions and even exceeding those of state-of-the-art Pt/C. Similar trends were also observed in both neutral and acid electrolytes. We deduce that, in this catalytic system, the enhanced electrocatalysis originates from the strain effect rather than the bifunctional mechanism. The present study builds a bridge between surface engineering and HER performance, and opens up new material designs for surface Pd-rich core–shell nanostructures for the purpose of improving HER catalytic activity and stability at all pH values. [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]

Asymmetrical etching of nanoparticles was achieved by employing interface-confined galvanic replacement reactions. Interfacial Ag nanocubes, nanowires and nanospheres were fabricated into symmetry-reduced cubic, trough-like and spherical nanocups, respectively. The formation of nanocups is attributed to in situ local nanomasking and selective etching of interfacial nanoparticles at the single-nanoparticle level. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a promising anode candidate for lithium-ion batteries (LIBs) owing to its unprecedented theoretical capacity of 4200 mA h g−1 and earth-abundant supply (26.2 wt%). Nevertheless, the huge volume expansion and unstable solid-electrolyte interface (SEI) of Si in multiple cycles make it very hard to simultaneously achieve high-energy and long-term cycle life for applications in large-scale renewable energy storage. Herein, we demonstrate a new class of Si/SiOx@void@nitrogen-doped carbon double-shelled hollow superstructure (Si/SiOx-DSHS) electrodes that are capable of accommodating huge volume changes without pulverization during cycling. Benefiting from the unique double-shelled hollow superstructure, Si/SiOx-DSHSs can facilitate the formation of a highly stable SEI layer and provide superior kinetics toward Li+-ion storage. The diffusion-controlled process and the capacitance-type reaction can work together to endow Si/SiOx-DSHSs with remarkable electrochemical characteristics, especially at high current density. These important characteristics make Si/SiOx-DSHSs deliver a large reversible capacity (1290 mA h g−1 at 0.1C), high first-cycle coulombic efficiency (71.7%), superior rate capability (360 mA h g−1 at 10C), and excellent cycling behavior up to 1000 cycles with a small capacity decay of 10.2%. The Si/SiOx-DSHSs are among the best Si-based anode materials for LIBs reported to date. [ABSTRACT FROM AUTHOR]

The electronic structure tuning of heterogeneous nanocatalysts is considered as one of the most effective ways of enhancing the catalytic activity of different chemical reactions. Herein, we demonstrate an effective way of tuning the electronic structure of networked PdAg nanowires (NWs) using polyvinylpyrrolidine imine (PVPI) as a new ligand to achieve more efficient hydrogen generation from formic acid (FA) decomposition. The PVPI-capped Pd5Ag5 NWs show the highest activity for the dehydrogenation catalysis of FA with an initial turnover frequency (TOF) of 242 h−1 among all the reported catalysts, and an increased TOF of 312 h−1 under 365 nm light irradiation at room temperature. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy studies reveal that there is an interfacial electron transfer from PVPI to the PdAg NW surface, which is the key factor in boosting the dehydrogenation catalysis of FA herein. Density functional theory calculations suggest that the high catalytic activity primarily stems from both electronegative Pd active centers and the imino group (C=N) in PVPI for efficiently deprotonating FA to Pd-formate intermediates and subsequently for promoting the cleavage of C–H. The PVPI-capped Pd5Ag5 NWs are very stable and reusable for FA dehydrogenation catalysis. [ABSTRACT FROM AUTHOR]

Depositing Pt atoms on nanoscale two-dimensional (2D) substrates resulting in the exposure of specific crystal facets is an effective strategy for reducing the Pt content without compromising the catalytic property. Herein, the Pd/PtCu core/shell nanoplates exhibit substantially improved ORR and MOR mass activities, 8.3 and 3.3 times higher than those of commercial Pt. The present work highlights the important role of designing a 2D core/shell nanostructure in enhancing fuel cell electrocatalysis. [ABSTRACT FROM AUTHOR]

The development of two-dimensional (2D) inorganic materials-based quantum dots (QDs) is still in its infancy but is triggering immense enthusiasm due to their high chemical stability, good aqueous dispersibility, excellent optical property, good biocompatibility and easy functionalization. This review covers almost all the extant 2D-QDs based on graphene, phosphorene, silicene, carbides, nitrides, transition metal dichalcogenide, transition metal oxides and MXenes, etc. Their categories, synthetic routes, properties, functionalization and applications are critically highlighted. In the application section, special emphasis is placed on the progress in bioimaging, cancer therapy, fluorescent sensing and optoelectronics. Meanwhile, the latest advances in 2D QDs-based catalysis and energy since 2015 are addressed. Moreover, 2D nanoclusters, in particular 2D-QDs, are also included. This review provides guidance for 2D-QDs studies to meet the increasing demands in the many diverse applications. [ABSTRACT FROM AUTHOR]

The ever-increasing power and energy demands for modern consumer electronics and electric vehicles are driving the pursuit of energy-storage technologies beyond the current horizon. Pseudocapacitive charge storage is one of the most effective and promising approaches to fill this technology gap, owing to its potential to deliver both high power and energy densities. Typically, titanium niobium oxides (TiNbxO2+2.5x (x = 2, 5 and 24)) with intrinsic pseudocapacitance, high safety and theoretical capacities of 388–402 mA h g−1 are recognized as promising anode materials for lithium-ion batteries. However, their poor conductivity and low Li+-ion diffusion coefficient are known to be the major hurdles limiting the full utilization of their pseudocapacitive effects, leading to their lackluster rate capabilities. Herein, we employ a facile electrospinning method to prepare one-dimensional hierarchically porous ZrNb24O62 nanowires (P-ZrNb24O62) with an ultra-large Li+-ion diffusion coefficient as a new intercalating pseudocapacitive material for boosting Li+-ion storage. The P-ZrNb24O62 exhibits excellent electrochemical performances, including a high reversible capacity (320 mA h g−1 at 0.1C), safe working potential (∼1.67 V vs. Li/Li+), high initial coulombic efficiency (90.1%), outstanding rate capability (182 mA h g−1 at 30C) and durable long-term cyclability (90.2% capacity retention over 1500 cycles). [ABSTRACT FROM AUTHOR]

Ti-based materials are well-known to be good anode materials for lithium ion batteries because of their negligible volume change during the charge/discharge process. Nevertheless, poor electronic conductivity makes them exhibit relatively low capacity. Herein, we report our design of three-dimensional hierarchical Li4Ti5O12–TiO2/MoO2 nanoclusters embedded into carbon nanosheets core/shell porous superstructures for achieving more efficient lithium ion storage. The resulting hybrid makes full use of the advantage of high-capacity MoO2 nanoclusters and robust Li4Ti5O12–TiO2 substrate as well as high-conductivity carbon nanosheets. Such an assembly is highly particular for not only endowing enhanced ion diffusion and rapid electron transfer, but also preventing MoO2 nanoclusters from agglomeration and oxidation. Benefitting from the advantageous structural feature and synergistic effect of the components, the Li4Ti5O12–TiO2@MoO2/C exhibits a high reversible specific capacity of 413 mA g−1 at a current density of 1000 mA g−1 up to 500 cycles, indicating its high stability. [ABSTRACT FROM AUTHOR]

The search for highly efficient earth-abundant carbon nanomaterials with Pt-like electrocatalytic activity for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) is still a great challenge. Herein, we present a new catalyst-free synthetic strategy of self-squeezing and rolling of B, N co-doped graphene nanosheets to nanotubes with tunable dimensions and atomic bonds as metal-free electrocatalysts for enhancing the ORR and HER using (polyethylene glycol (PEG)) as the directing agent. We found that the PEG with a higher molecular weight favors the formation of B, N co-doped graphene nanosheets with a high concentration of B–N bonds in a carbon framework whereas the one with a lower molecular weight leads to B, N co-doped graphene nanotubes (BCN nanotubes) with segregated B–C and N–C bonds. The as-prepared graphene nanostructures show interesting atomic bonds and dimension-dependent electrocatalytic activity towards the ORR and HER with BCN nanotubes being the best. The BCN nanotubes show Pt-like ORR activity and much better ORR stability than commercial Pt/C catalysts. They also exhibit excellent HER activity with a very low overpotential and a small Tafel slope of 92 mV dec−1. The present work highlights the importance of tuning atomic bonds and dimensions of carbon nanomaterials for achieving highly efficient electrocatalysts for the ORR and HER. [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]

One of the critical issues in the industrial development of fuel cells (e.g., proton exchange membrane fuel cells, direct methanol fuel cells and biofuel cells) is the high cost, serious intermediate tolerance, anode crossover, sluggish kinetics, and poor stability of the platinum (Pt) as the preferred electrocatalysts for the oxygen reduction reaction (ORR) at the cathode. The development of novel noble-metal-free electrocatalysts with low cost, high activity and practical durability for ORR has been considered as one of the most active and competitive fields in chemistry and materials science. In this critical review, we will summarize recent advances on engineering advanced carbon nanomaterials with different dimensions for the rational design and synthesis of noble-metal-free oxygen reduction electrocatalysts including heteroatom-doped carbon nanomaterials, transition metal-based nanoparticle (NP)–carbon nanomaterial composites and especially the stable iron carbide (Fe3C)-based NP–carbon nanomaterial composites. Introducing advanced carbon nanomaterials with high specific surface area and stable structure into the noble-metal-free ORR field has not only led to a maximized electrocatalyst surface area for the electron transfer but also resulted in enhanced electrocatalyst stability for long-term operation. Therefore, the rational design and synthesis of noble-metal-free electrocatalysts based on heteroatoms, transition metal-based NPs and Fe3C-based NP functionalized carbon nanomaterials are of special relevance for their ORR applications, and represents a rapidly growing branch of research. The demonstrated examples in this review will open new directions on designing and optimizing advanced carbon nanomaterials for the development of extremely active and durable earth-abundant cathodic catalysts for fuel cell applications. [ABSTRACT FROM AUTHOR]

Enhancing the nitrogen (N) doping in carbon nanomaterials has been suggested as an effective approach to enhance the performance of lithium ion batteries (LIBs). However, achieving N-doped carbon nanomaterials with an ultrahigh N content is still a great challenge, thus limiting the capacity enhancement. Herein, we demonstrate a new procedure for the synthesis of unique sandwich architecture of N-doped carbon/reduced graphene oxide (N-carbon/rGO) derived from simple pyrolysis of a polypyrrole/GO nanosheet precursor. The N-carbon/rGO exhibits the highest N-doping of 15.4% reported in all the carbon-based nanomaterials, and a high specific surface area of 327 m2 g−1 with a micro/mesoporous structure. They combine the advantages of high conductivity of rGO, very high N-functionalities, and the porous structure of carbons, which endow them with appealing electrochemical lithium storage properties with a high initial reversible capacity of 1100 mA h g−1 at 100 mA g−1, excellent rate capability up to 20 A g−1, and superior cycling stability over 1000 cycles at a high current density of 1 A g−1. The present work highlights the important role of tuning the nitrogen doping in enhancing the performance of LIBs. [ABSTRACT FROM AUTHOR]

To well understand the effect of the mesopore type of ordered mesoporous carbons (OMCs) on enhancing energy storage and conversion is still a great challenge because of the extreme difficulties in exploring new methods to create OMCs with different types of mesopores. Herein, we develop an intriguing dual-templating co-assembly/hydrothermal approach to realize nanostructure engineering in OMCs with various types of mesopores from three-dimensional (3D) cubic (OMCNW-c) to 2D hexagonal mesopores (OMCNW-h) and 0D mesoporous carbon nanospheres (OMC-S) for their electrochemical performance optimization in supercapacitors and oxygen reduction reactions (ORRs). The results show that OMCNW-c exhibits a specific capacitance of 215 F g−1 at 0.5 A g−1, higher than those of OMCNW-h and OMC-S, good capability and excellent cycling performance with no capacity fading even after 10 000 cycles. Furthermore, OMCNW-c shows much better electrocatalytic activity for ORR than OMCNW-h and OMC-S. The present investigations give strong evidence that tuning mesopore type of OMCs can contribute another important factor in enhancing catalysis and energy storage. We believe that the present synthetic strategy for different types of mesoporous nanomaterials with desirable structure and morphology can open a new approach to future novel mesoporous materials for greatly improved catalytic and energy applications. [ABSTRACT FROM AUTHOR]

Herein, we report a facile strategy that allows one-pot preparation of highly open rhombic dodecahedral PtCu alloy nanoframes. Due to the highly open structures, the PtCu nanoframes exhibit enhanced catalytic performance in methanol electrooxidation, showing a new strategy to create highly active catalysts. [ABSTRACT FROM AUTHOR]

An efficient synthetic approach that enables not only the control of Pt nanocubes but also the one-pot fabrication of novel Pt nanocube assemblies was developed for the first time. The integration of well-defined building blocks and unique superstructures endows Pt nanocube assemblies with enhanced performance in the methanol electrooxidation, showing a new concept for further enhancing the performance of these catalysts. [ABSTRACT FROM AUTHOR]

The emergence of graphene nanosheet (GN, 2010 Nobel Prize for Physics) has recently opened up an exciting new field in the science and technology of two-dimensional (2D) nanomaterials with continuously growing academic and technological impetus. GN exhibits unique electronic, optical, magnetic, thermal and mechanical properties arising from its strictly 2D structure and thus has many important technical applications. Actually, GN-based materials have enormous potential to rival or even surpass the performance of carbon nanotube-based counterparts, given that cheap, large-scale production and processing methods for high-quality GN become available. Therefore, the studies on GN in the aspects of chemistry, physical, materials, biology and interdisciplinary science have been in full flow in the past five years. In this critical review, from the viewpoint of chemistry and materials, we will cover recent significant advances in synthesis, molecular engineering, thin film, hybrids, and energy and analytical applications of the “star-material” GN together with discussion on its major challenges and opportunities for future GN research (315 references). [ABSTRACT FROM AUTHOR]

A novel and facile process is reported for water-phase synthesis of high-quality graphene/TiO2composite nanosheets (GTCN) on a large scale using TiCl3as both a reducing agent and a precursor. [ABSTRACT FROM AUTHOR]

A significant increase (ca.22-fold) in the electricity generation due to a Shewanella oneidensisMR-1 biofilm was observed in the presence of Fe3O4/Au nanocomposites. [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.

This work provides a roll-to-roll processed flexible multi-responsive smart film containing tungsten bronze nanorods and a phase-separated liquid crystal-polymer composite, which can reversibly control the passage of visible light in response to temperature, an electric field and near infrared light, and also screen the heat rays from 800 nm to 2500 nm.

Herein we propose novel photoelectrochemical fuel cells (PEFCs) by the introduction of a solid-state Ag2O/Ag cathode (here also term as photoelectrochemical battery). Due to the superior electrochemical properties of Ag2O/Ag, the maximum power density of our PEFCs can reach 0.94 mW cm(-2) upon UV illumination. Furthermore, our PEFCs have stable cycle operation and can be undertaken in a single chamber without an ion-exchange membrane. Most importantly, we demonstrate that our PEFCs can be adopted to degrade the methyl orange (MO) dye with a decomposition percentage of 72.5% within 30 min during the PEFC process.

A new electrochemical label-free biosensor based on target-induced conjunction of a split aptamer as new chiral selector for oligopeptide using graphene-mesoporous silica-gold NP hybrids (GSGHs) as magnified sensing platform is firstly reported, which showed high sensitivity and selectivity for the detection of D-vasopressin (D-VP)., (This journal is © The Royal Society of Chemistry 2012)

The appearance of the aptamer provides good recognition elements for small molecules, especially for drugs. In this work, by combining the advantages of magnetic nanoparticles (MNPs) with colorimetric drug detection using hemin-G-quadruplex complex as the sensing element, we report a simple and sensitive DNAzyme-based colorimetric sensor for cocaine detection in a 3,3,5,5-tetramethylbenzidine sulfate (TMB)-H(2)O(2) reaction system. The whole experimental processes are simplified. Cocaine aptamer fragments, SH-C2, are covalently labeled onto the amine-functionalized MNPs. When the target cocaine and another cocaine aptamer fragments (C1) grafted with G-riched strand AG4 (i.e. C1-AG4) are present simultaneously, the C2 layer on MNPs hybridizes partly with C1-AG4 to bind the cocaine. The C1-AG4 can be combinded with hemin to form DNAzyme which can effectively catalyze the H(2)O(2)-mediated oxidation of TMB, giving rise to a change in solution color. Importantly, using MNPs as the separation and amplification elements could effectively reduce the background signal and the interference from the real samples. A linear response from 0.1 μM to 20 μM is obtained for cocaine and a detection limit of 50 nM is achieved, which provides high sensitivity and selectivity to detect cocaine.

We for the first time report a facile, wet-chemical strategy for the high-yield (approximately 100%) synthesis of ultralong Pt-on-Pd bimetallic nanowires (NWs) with the cores being Pd NWs and the shells being made of dendritic Pt, which exhibit high surface area and enhanced electrocatalytic activity towards methanol oxidation reaction.

SERS aptasensors for protein recognition based on Au nanoparticles labeled with aptamers and Raman reporters have been developed, which opens a new way for protein recognition of high sensitivity and selectivity.