High-entropy wire-on-sheet nanoarray catalyst with boosted pre-oxidation for efficient oxygen evolution reaction.

Herein, a septenary NiCoZnFeCuMnCe hydroxide nanoarray catalyst with a unique wire-on-sheet morphology and high-entropy feature was fabricated, which exhibits boosted pre-oxidation behavior and synergistically enhanced catalytic activity and durability towards the oxygen evolution reaction.

Topotactic synthesis of high-entropy sulfide nanosheets as efficient pre-catalysts for water oxidation.

Herein, quinary CoFeNiCuCr sulfide nanosheets with a high-entropy feature and rough surface were fabricated via a topotactic transformation pathway from high-entropy layered metal hydroxides, and display facile pre-oxidation and improved intrinsic activity towards the robust oxygen evolution reaction.

Promising Mass-Productive 4-Inch Commercial SERS Sensor with Particle in Micro-Nano Porous Ag/Si/Ag Structure Using in Auxiliary Diagnosis of Early Lung Cancer.

The construction of commercial surface enhanced Raman scattering (SERS) sensors suitable for clinical applications is a pending problem, which is heavily limited by the low production of high-performance SERS bases, because they usually require fine or complicated micro/nano structures. To solve this issue, herein, a promising mass-productive 4-inch ultrasensitive SERS substrate available for early lung cancer diagnosis is proposed, which is designed with a special architecture of particle in micro-nano porous structure. Benefitting from the effective cascaded electric field coupling inside the particle-in-cavity structure and efficient Knudsen diffusion of molecules within the nanohole, the substrate exhibits remarkable SERS performance for gaseous malignancy biomarker, with the limit of detection is 0.1 ppb and the average relative standard deviation value at different scales (from cm2 to µm2 ) is ≈16.5%. In practical application, this large-sized sensor can be further divided into small ones (1 × 1 cm2 ), and more than 65 chips will be obtained from just one 4-inch wafer, greatly increasing the output of commercial SERS sensor. Further, a medical breath bag composed of this small chip is designed and studied in detail here, which suggested high-specificity recognition for lung cancer biomarker in mixed mimetic exhalation tests.

Lattice-disordered high-entropy metal hydroxide nanosheets as efficient precatalysts for bifunctional electro-oxidation.

Electro-oxidation reactions (EORs) are important half reactions in overall and assisted water electrolysis, which are crucial in achieving economic and sustainable hydrogen production and realizing simultaneous wastewater treatment. Current studies indicate that the high-valence metal ions that are locally enriched in the catalysts or generated in situ during the anodic preoxidation process are active species for EORs. Hence, designing (pre)catalysts with enriched local active sites and boosted preoxidation is of great importance. In this work, with a focus on improving the EOR performance toward the oxygen evolution reaction (OER) and the urea oxidation reaction (UOR), we fabricated a lattice-disordered high-entropy FeCuCoNiZn hydroxide nanoarray catalyst that exhibits robust bifunctional OER and UOR behavior. The high-entropy feature could bring in a unique catalytic ensemble effect and remarkably improve the intrinsic OER/UOR activity. The lattice-disordered structure could not only enrich the local high-valence metal ions as active sites but also provide abundant reactive surface sites to accelerate the preoxidation process, thus leading to enriched active sites for the OER and UOR. Benefitting from the structural merits, the lattice-disordered high-entropy catalyst exhibits excellent OER and UOR activity with low overpotential, large current density and enhanced intrinsic activity, and no performance degradation but dramatic 35.3% and 88.7% enhancement in activity can be achieved during the long-term OER and UOR tests, respectively. The robust OER and UOR performance makes the lattice-disordered high-entropy catalyst a promising candidate for overall and urea-assisted water electrolysis from industrial, agricultural and sanitary wastewater.

Dual-oxidation-induced lattice disordering in a Prussian blue analog for ultrastable oxygen evolution reaction performance.

Enriching the active sites and enhancing the intrinsic activity of a single site are two basic strategies for improving the activity toward the electrocatalytic oxygen evolution reaction (OER), and designing an advanced microstructure with a boosted pre-oxidation process can further guarantee durability toward long-term catalysis. Herein, we propose a dual oxidation strategy of a Co Prussian blue analog (Co PBA), which simultaneously achieves Co3+ active site enrichment, in situ CeO2 decoration and lattice disordering with abundant undercoordinated sites, realizing highly efficient and ultrastable OER performance. The dual oxidation process can induce the enrichment of high-valence Co ions by combined chemical oxidation and d-f electron coupling compared to the singly oxidized catalysts, thereby providing more active sites with enhanced intrinsic activity for the early triggered OER process. In addition, the disordered lattice can provide abundant reactive Co sites for the pre-oxidation process, thereby leading to obvious activation of the catalysts and remarkable operational stability due to the substantially accumulated Co3+ sites. Benefitting from the structural advantages of lattice-disordered dual-oxidized Co PBA nanocages, a low overpotential of 240 mV can be achieved for a 10 mA cm-2 current density, and the large catalytic current density and intrinsic activity are among the best compared to those of previously reported PBA-based and PBA-derived catalysts and even RuO2 and IrO2. In addition, ultrastable OER behavior with a 263 % activity enhancement in 150 h can result, making the dual-oxidized catalyst a promising candidate for water electrolysis.

High-entropy amorphous oxycyanide as an efficient pre-catalyst for the oxygen evolution reaction.

Herein, a high-entropy amorphous oxycyanide porous nanocube pre-catalyst was developed for the oxygen evolution reaction (OER). Benefitting from the facile pre-oxidation and enhanced intrinsic activity of the high-entropy catalyst, a highly efficient and ultrastable OER performance was achieved.

Oriented interlayered charge transfer in NiCoFe layered double hydroxide/MoO3 stacked heterostructure promoting the oxygen-evolving behavior.

Oxygen evolution reaction (OER), the rate-limiting half reaction of water electrolysis, plays as a crucial role in improving the overall efficiency of the coupled hydrogen evolution. To date, earth-abundant OER catalysts have been extensively studied, while unfortunately their catalytic activity and operational stability still need to be further optimized. In this work, we fabricated a highly efficient OER catalyst based on two-dimensional (2D) NiCoFe layered double hydroxide (LDH)/MoO3 stacked heterostructure with enriched active sites and optimal electronic structure via an electrostatic-driven self-assembly process. The rough surface of the 2D heterostructure could offer abundant reactive sites for the pre-oxidation reaction, thereby leading to fast generation of the high-valence active species for OER, and the multi-metal synergy and oriented interlayered charge transfer could further enhance the intrinsic OER activity, finally resulting in enhanced OER performance with low overpotential, large current density, high intrinsic activity and excellent operational stability.

Particle-in-Molybdenum Disulfide-Coated Cavity Structure with a Raman Internal Standard for Sensitive Raman Detection of Water Contaminants from Ions to <300 nm Nanoplastics.

To develop a universal and precise detection strategy that can be applied to water contaminants of various sizes, we designed a particle-in-MoS2 coated cavity structure of AAO/MoS2/Ag with a Raman internal standard. This modified particle-in-cavity structure not only successfully integrates both "surface hot spots" and "volume hot spots" via dressing and manipulating the cascaded optical-field mode inside the cavity but also introduces the chemical enhancement and internal standard attribute of MoS2. Because of its unique three-dimensional structure, AAO/MoS2/Ag accurately detects water contaminants of various sizes from ions to nanoplastics (<300 nm) for the first time. This work proposes a novel and universal surface-enhanced Raman scattering strategy for detecting multiple-size water contaminants and demonstrates the potential to build a security line in early warning systems for the prevention of water pollution.

Acceleration of the pre-oxidation process by tuning the degree of sulfurization for promoted oxygen evolution reaction.

In this work, Co-based nanocatalysts with variable degrees of sulfurization (DoS) were fabricated for the oxygen evolution reaction (OER). The partially sulfurized catalyst with a medium DoS could exhibit a promoted pre-oxidation process, leading to a highly efficient and ultrastable OER performance.

Cerium-induced lattice disordering in Co-based nanocatalysts promoting the hydrazine electro-oxidation behavior.

In this work, cerium-incorporated Co-based catalysts encapsulated in nitrogen-doped carbon were fabricated for the electrocatalytic hydrazine oxidation reaction (HzOR). The Ce incorporation could lead to the formation of surface oxide nanolayers with a disordered lattice, endowing the catalyst with enriched active sites and enhanced intrinsic activity for promoted HzOR.

Precise real-time quantification for photocatalytic reaction: integration of the sensitivein-situSERS sensor and high-efficiency photocatalyst.

Recently,in-situsurface-enhanced Raman spectroscopy (SERS) is gradually becoming an important method for monitoring photocatalytic reaction processes, in which the quantification potential is a vital factor in determining whether this technology can be truly applied in the future. In order to improve the quantification performance ofin-situSERS and explore a precise operando Raman detection for photocatalytic reactions, an architecture of heterostructural Cu2O/ZnO/Ag nano round brush has been designed and discussed in this work. This structure is an integration of sensitivein-situSERS sensor and high-efficiency photocatalyst, realizing real-time monitoring of photocatalytic reaction in a wide concentration range from 20 to 3 mg l-1. The coefficient of determination between different detection methods is beyond 0.86 in this range, implying the high-precise quantification of this platform. Comprehensive analysis on structure effect, SERS performance, photocatalytic property, electric filed characteristic, etc were all systematically made and discussed in detail for this platform. This work presents a precise preliminar real-time photocatalytic monitoring usingin-situSERS detection, which is a new attempt and also meaningful reference for otherin-situanalytical technology.

Recent advances in the pre-oxidation process in electrocatalytic urea oxidation reactions.

The electrocatalytic urea oxidation reaction (UOR) has attracted substantial research interests over the past few years owing to its critical role in coupled electrochemical systems for energy conversion, for example, coupling with the hydrogen evolution reaction (HER) to realize urea-assisted hydrogen production and assembling direct urea fuel cells (DUFC) by coupling with the oxygen reduction reaction (ORR). The UOR process has been proved to be a two-step process which involves an electrochemical pre-oxidation reaction of the metal sites and a subsequent chemical oxidation of the urea molecules on the as-formed high-valence metal sites. Hence, designing advanced (pre-)catalysts with a boosted pre-oxidation reaction is of great importance in improving the UOR performance and thus accelerating the coupled reactions. In this feature article, we discuss the significant role of the pre-oxidation process during the urea electro-oxidation reaction, and summarize detailed strategies and recent advances in promoting the pre-oxidation reaction, including the modulation of the crystallinity, active phase engineering, defect engineering, elemental incorporation and constructing hierarchical nanostructures. We anticipate that this feature article will offer helpful guidance for the design and optimization of advanced (pre-)catalysts for UOR and related energy conversion applications.

Cobalt, iron co-incorporated Ni(OH)2 multiphase for superior multifunctional electrocatalytic oxidation.

The cobalt, iron co-incorporated Ni(OH)2 multiphase displays superior catalytic activity and stability for multifunctional electrocatalytic oxidation, ascribed to the multiphase synergy, enhanced charge transfer and well-exposed active sites.

Preparation of a superhydrophobic AgNP/GF substrate and its SERS application in a complex detection environment.

Surface-enhanced Raman scattering (SERS) is widely considered to be a fingerprint spectrum that can realize molecular identification, and it continues to receive a lot of attention due to its high sensitivity and powerful qualitative analysis capabilities. In recent years, there has been a lot of work and reports on super-sensitive SERS substrates, but often the enhanced ability of the substrate is also effective for impurities and irrelevant molecules. Therefore, a problem that still remains to be solved is how to perform effective trace detection of specific substances in a complex detection environment. Herein, a superhydrophobic Ag nanoparticle/glass microfibre filter (AgNP/GF) substrate was designed to realize the Raman detection of complex multiphase solutions. The hydrophobic three-dimensional net-like structure provides efficient Raman enhancement, making the substrate have extremely high detection limits for dye molecules and even achieving specific detection of the hexane phase component (thiram molecule) in a multiphase solution.

"Pit-dot" ultrathin nanosheets of hydrated copper pyrophosphate as efficient pre-catalysts for robust water oxidation.

Herein, hydrated copper pyrophosphate ultrathin nanosheets with a unique "pit-dot" nanostructure were fabricated as efficient pre-catalysts for the oxygen evolution reaction, and systematic post-catalytic characterization studies confirmed the important role of the boosted pre-oxidation reaction in promoting the OER catalysis.

Heterostructured Cu2O-Au nanowire as a dual-functional nanocomposite for environmental pollutant degradation and hydrogen peroxide sensing.

Materials engineering is generally regarded as one of the most effective methods in the construction of photocatalysts, but it still faces many challenges. In this context, we designed and prepared a three-dimensional (3D) heterostructure of nanowires (NWs) formed by Cu2O core and an Au shell. The Cu2O-Au NWs not only show fine photocatalytic ability but also proved to have Fenton-like chemical properties and can be used as a hydrogen peroxide sensor. Moreover, this heterostructure realizes an integration of catalytic efficiency, retrievability, and versatility. In further consideration of the facile preparation process and low-cost material source of the structure, the Cu2O-Au NWs show a promising application prospect in the field of multifunctional photocatalysts.

SERS substrate with wettability difference for molecular self-concentrating detection.

The surface-enhanced Raman spectroscopy (SERS) has attracted much attention due to the powerful capability of quantificational analysis. Nowadays, most of the enhancement effect by SERS substrate is provided by the 'hot spots' occupying relatively small space. When the amount of analyte is too low, it is difficult to ensure that all the probe molecules can be placed into the 'hot spots', which is a headache in SERS quatification. In order to solve this problem, we have developed a structure of CuO nanowires/Ag nanoparticles with wettability capacity difference, which can aggregate molecules in water and oil simultaneously under two different mechanisms. The limit of detection and enhancement factor of this structure are estimated as 10-15M and 1.55 × 1011respectively (for rhodamine 6G, R6G). In a proof-in-principle experiment of sewage detection, it successfully achieved the aggregation and additional enhancement of both the R6G molecules in aqueous solution and thiuram molecules in toluene, realizing efficient and accurate Raman detection.

In-plane ß-Co(OH)2/Co3O4 hybrid nanosheets for flexible all-solid-state thin-film supercapacitors with high electrochemical performance.

With the increasing demand for portable electronic devices, efficient power supplies with ultraflexibility have received considerable attention, among which the all-solid-state thin-film supercapacitors (ASSTFSs) have been considered as promising candidates for powering the portable devices with high performance and safety. In this work, we proposed in-plane ß-Co(OH)2/Co3O4 hybrid nanosheets with porous surface and controllable composition, which could be assembled as flexible electrodes for ASSTFSs. As the two-dimensional (2D) matrix of the hybrid nanosheets, the porous ß-Co(OH)2 component could offer a large surface area, thereby exposing more surface sites for surface redox reactions; the conductive Co3O4 component could effectively improve the intrinsic conductivity of the electrode material, thereby realizing good electrochemical performance synergistically. With the merits of the synergistic structural benefits, the ASSTFS device based on the ß-Co(OH)2/Co3O4 hybrid nanosheets exhibits high specific capacitance with good cycling stability and ultraflexibility, making our device an outstanding candidate for practical power supply in electronic devices.

Hierarchical Particle-In-Quasicavity Architecture for Ultratrace In Situ Raman Sensing and Its Application in Real-Time Monitoring of Toxic Pollutants.

Unstable detection environment is one of the biggest interferences for in situ surface-enhanced Raman spectroscopy (SERS) using in real-time monitoring of toxic pollutants, leading to unreliable results. To address this problem, we have designed and prepared a cavity-based particle-in-quasicavity (PIQC) architecture composed of hierarchical ZnO/Ag nanosheets and nanoprotrusions for improving the in situ SERS performance under a liquid environment. Benefitting from the special cascaded optical field mode, the PIQC ZnO/Ag exhibits excellent in situ SERS detectability, with 10-18 M of limit of detection for rhodamine 6G and 12.8% of signal relative standard deviation value. Furthermore, by means of a microfluidic chip, this PIQC structure is proved to have the quantitative analysis feasibility and realizes real-time monitoring of the 3,3',4,4'-tetrachlorobiphenyl, a representative global environmental hazard, under the flowing environment. The strategy in this paper provides a brand new idea to promote the application of in situ SERS in contaminant monitoring and is also instructive for light control in other optical fields.

Modulation of electronic structures in two-dimensional electrocatalysts for the hydrogen evolution reaction.

The electrocatalytic hydrogen evolution reaction (HER) has attracted substantial attention owing to its important role in realizing economic and sustainable hydrogen production via water electrolysis. Designing two-dimensional (2D) materials with large surface area, highly exposed surface sites and facile charge transport pathways is highly attractive for promoting the HER activity of the earth-abundant catalysts, and conducting rational modulations in the electronic structures is considered to be promising in further optimizing the intrinsic HER activity and thus realizing promoted HER performance. In this Feature Article, we systematically summarize recent progress in the modulation of the electronic structures of 2D HER electrocatalysts via multiple strategies including elemental doping, formation of alloyed structures, defect engineering, facet engineering, phase regulation, interface engineering and hybridization of the nanocatalysts with 2D substrates, and discuss the role of electronic structures in optimizing the intrinsic HER activity of 2D HER catalysts. We anticipate that this Feature Article will offer helpful guidance for oriented design and optimization of efficient electrocatalysts for scalable and economic hydrogen production.