Carbon-Quantum-Dots-Loaded Ruthenium Nanoparticles as an Efficient Electrocatalyst for Hydrogen Production in Alkaline Media

Tuning the electronic metal-carbon interactions in Lignin-based carbon-supported ruthenium-based electrocatalysts for enhanced hydrogen evolution reactions

Ruthenium (Ru) nanoparticles dispersed on carbon support are promising electrocatalysts for hydrogen evolution reaction (HER) due to strong electronic metal-carbon interactions (EMCIs). Defects engineering in carbon supports is an effective strategy to adjust EMCIs. We prepared nitrogen/sulfur co-doped carbon supported Ru nanoparticles (Ru@N/S-LC) using sodium lignosulfonate and urea as feedstocks. Intrinsic S dopants from sodium lignosulfonate create rich S defects, thus enhancing the EMCIs within Ru@N/S-LC, leading a faster electron transfer between Ru nanoparticles and N/S-LC compared with N-doped carbon supported Ru nanoparticles (Ru@N-CC). The resulting Ru@N/S-LC exhibits an enhanced work function and a down-shifted d-band center, inducing stronger electron capturing ability and weaker hydrogen desorption energy than Ru@N-CC. Ru@N/S-LC requires only 7 and 94 mV overpotential in acidic medium and alkaline medium to achieve a current density of 10 mA cm-2. Density Functional Theory (DFT) calculations were utilized to clarify the impact of sulfur (S) doping and the mechanism underlying the notable catalytic activity of Ru@N/S-LC. This study offers a perspective for utilizing the natural dopants of biomass to adjust the EMCIs for electrocatalysts.

Ultrafine CoRu alloy nanoclusters densely anchored on Nitrogen-Doped graphene nanotubes for a highly efficient hydrogen evolution reaction

Designing highly efficient and stable electrocatalysts for hydrogen evolution reactions (HER) is essential to the production of green and renewable hydrogen. Metal-organic framework (MOF) precursor strategies are promising for the design of excellent electrocatalysts because of their porous architectures and adjustable compositions. In this study, a hydrogen-bonded organic framework (HOF) nanowire was developed as a precursor and template for the controllable and scalable synthesis of CoRu-MOF nanotubes. After calcination in Ar, the CoRu-MOF nanotubes were converted into N-doped graphene (NG) nanotubes with ultrafine CoRu nanoclusters (hereon called Co-xRu@NG-T; x  = 0, 5, 10, 15, 25 representing the Ru content of 0-0.25 mmol; T = 400 °C to 700 °C) that were densely encapsulated and isolated on the shell. Taking advantage of the synergistic effects of the porous, one-dimensional hollow structure and ultrafine CoRu nanoclusters, the optimized Co-15Ru@NG-500 catalyst demonstrated superior catalytic performance for HERs in alkaline electrolytes with an overpotential of only 30 mV at 10 mA cm-2 and robust durability for 2000 cycles, which outperforms many typical catalytic materials, such as commercial Pt/C. This work introduces a novel high-efficiency and cost-effective HER catalyst for application in commercial water-splitting electrolysis.

Photocatalytic Hydrogen Production with A Molecular Cobalt Complex in Alkaline Aqueous Solutions

The thermodynamic favorability of an alkaline solution for the oxidation of water suggests the need for developing hydrogen evolution reaction (HER) catalysts that can function in basic aqueous solutions so that both of the half reactions in overall water splitting can occur in mutually compatible solutions. Although photocatalytic HERs have been reported mostly in acidic solutions and a few at basic pHs in mixed organic aqueous solutions, visible-light driven HER catalyzed by molecular metal complexes in purely alkaline aqueous solutions remains largely unexplored. Here, we report a new cobalt complex with a tetrapyridylamine ligand that catalyzes photolytic HER with turnover number up to 218 000 in purely aqueous solutions at pH 9.0. Density functional theory (DFT) calculations suggested a modified electron transfer (E)-proton transfer (C)-electron transfer (E)-proton transfer (C) (mod-ECEC) pathway for hydrogen production from the protonation of CoII-H species. The remarkable catalytic activity resulting from subtle structural changes of the ligand scaffold highlights the importance of studying structure-function relationships in molecular catalyst design. Our present work significantly advances the development of a molecular metal catalyst for visible-light driven HER in more challenging alkaline aqueous solutions that holds substantial promise in solar-driven water-splitting systems.

Rational Regulation of the Defect Density in Platinum Nanocrystals for Highly Efficient Hydrogen Evolution Reaction

Constructing structural defects is a promising way to enhance the catalytic activity toward the hydrogen evolution reaction (HER). However, the relationship between defect density and HER activity has rarely been discussed. In this study, a series of Pt/WOx nanocrystals are fabricated with controlled morphologies and structural defect densities using a facile one-step wet chemical method. Remarkably, compared with polygonal and star structures, the dendritic Pt/WOx (d-Pt/WOx) exhibited a richer structural defect density, including stepped surfaces and atomic defects. Notably, the d-Pt/WOx catalyst required 4 and 16 mV to reach 10 mA cm-2, and its turnover frequency (TOF) values are 11.6 and 22.8 times higher than that of Pt/C under acidic and alkaline conditions, respectively. In addition, d-Pt/WOx//IrO2 displayed a mass activity of 5158 mA mgPt -1 at 2.0 V in proton exchange membrane water electrolyzers (PEMWEs), which is significantly higher than that of the commercial Pt/C//IrO2 system. Further mechanistic studies suggested that the d-Pt/WOx exhibited reduced number of antibonding bands and the lowest dz2-band center, contributing to hydrogen adsorption and release in acidic solution. The highest dz2-band center of d-Pt/WOx facilitated the adsorption of hydrogen from water molecules and water dissociation in alkaline medium. This work emphasizes the key role of the defect density in improving the HER activity of electrocatalysts.

Low-loaded Ru on hollow SnO2 for enhanced electrocatalytic hydrogen evolution

In response to the challenges of intermediate poisoning and the high cost of noble metal catalysts in the hydrogen evolution reaction (HER), we develop a Ru-doped SnO2 catalyst. This Ru-SnO2 catalyst has the characteristics of low Ru loading and a hollow structure, which endow it with good electrocatalytic activity and stability for the HER.

Confining N-Doped Carbon Dots into PtNi Aerogels Skeleton for Robust Electrocatalytic Methanol Oxidation and Oxygen Reduction

Noble metallic aerogels with the self-supported hierarchical structure and remarkable activity are promising for methanol fuel cells, but are limited by the severe poisoning and degradation of active sites during electrocatalysis. Herein, the highly stable electrocatalyst of N-doped carbon dots-PtNi (NCDs-PtNi) aerogels is proposed by confining NCDs with alloyed PtNi for methanol oxidation and oxygen reduction reactions. Comprehensive electrocatalytic measurements and theoretical investigations suggest the improvement in structure stability and regulation in electronic structure for better electrocatalytic durability when confining NCDs with PtNi aerogels. Notably, the NCDs-PtNi aerogels perform 12-fold higher activity than that of Pt/C and maintain 52% of their initial activity after 5000 cycles toward acidic methanol oxidation. The enhanced stability and activity of NCDs-PtNi aerogels are also evident for oxygen reduction reactions in different electrolytes. These results highlight the effectiveness of stabilizing metallic aerogels with NCDs, offering a feasible pathway to develop robust electrocatalysts for fuel cells.

Facilitating alkaline hydrogen evolution reaction on the hetero-interfaced Ru/RuO2 through Pt single atoms doping

Exploring an active and cost-effective electrocatalyst alternative to carbon-supported platinum nanoparticles for alkaline hydrogen evolution reaction (HER) have remained elusive to date. Here, we report a catalyst based on platinum single atoms (SAs) doped into the hetero-interfaced Ru/RuO2 support (referred to as Pt-Ru/RuO2), which features a low HER overpotential, an excellent stability and a distinctly enhanced cost-based activity compared to commercial Pt/C and Ru/C in 1 M KOH. Advanced physico-chemical characterizations disclose that the sluggish water dissociation is accelerated by RuO2 while Pt SAs and the metallic Ru facilitate the subsequent H* combination. Theoretical calculations correlate with the experimental findings. Furthermore, Pt-Ru/RuO2 only requires 1.90 V to reach 1 A cm-2 and delivers a high price activity in the anion exchange membrane water electrolyzer, outperforming the benchmark Pt/C. This research offers a feasible guidance for developing the noble metal-based catalysts with high performance and low cost toward practical H2 production.

Hollow Ru/RuO2 nanospheres with nanoparticulate shells for high performance electrocatalytic oxygen evolution reactions

This work shows that hollow Ru/RuO2 nanoparticles having nanoparticulate shells (HN-Ru/RuO2) can be prepared using hollow microporous organic polymers with Ru species (H-MOP-Ru) as precursors. Using silica spheres as templates, H-MOPs were prepared through the Sonogashira-Hagihara coupling of 1,3,5-triethynylbenzene with 2,3-ethoxymethylenedioxy-1,4-diiodobenzene. Acid hydrolysis of cyclic ethyl orthoformate protecting groups generated catechol moieties to form H-MOP-Cat. Then, H-MOP-Ru was obtained by incorporating Ru species into H-MOP-Cat. Heat-treatment of H-MOP-Ru under air induced the formation of HN-Ru/RuO2 with a diameter of 61 nm and shells consisting of 6-7 nm nanoparticles. Due to the hollow structure and nanoparticulate shells, HN-Ru/RuO2 showed a high surface area of 80 m2 g-1 and a pore volume of 0.18 cm3 g-1. The HN-Ru/RuO2 showed enhanced electrocatalytic performance for the oxygen evolution reaction (OER) with an overpotential of 295 mV @ 10 mA cm-2 and a Tafel slope of 46 mV dec-1 in alkaline electrolyte, compared with control RuO2 such as commercial Ru/RuO2 nanoparticles (A-Ru/RuO2) and home-made Ru/RuO2 nanoparticles (N-Ru/RuO2) prepared via the same synthetic procedure as HN-Ru/RuO2. While HN-Ru/RuO2 inevitably contained Pd originated from coupling catalysts, it showed superior performance to Ru/RuO2 nanoparticles with the same Pd content (N1-Ru/RuO2), indicating that the efficient electrocatalytic performance of HN-Ru/RuO2 is attributable to its hollow structure and nanoparticulate shells.

Ambient γ-Rays-Mediated Noble-Metal Deposition on Defect-Rich Manganese Oxide for Glycerol-Assisted H2 Evolution at Industrial-Level Current Density

Developing novel synthesis technologies is crucial to expanding bifunctional electrocatalysts for energy-saving hydrogen production. Herein, we report an ambient and controllable γ-ray radiation reduction to synthesize a series of noble metal nanoparticles anchored on defect-rich manganese oxides (M@MnO2-x , M=Ru, Pt, Pd, Ir) for glycerol-assisted H2 evolution. Benefiting from the strong penetrability of γ-rays, nanoparticles and defect supports are formed simultaneously and bridged by metal-oxygen bonds, guaranteeing structural stability and active site exposure. The special Ru-O-Mn bonds activate the Ru and Mn sites in Ru@MnO2-x through strong interfacial coordination, driving glycerol electrolysis at low overpotential. Furthermore, only a low cell voltage of 1.68 V is required to achieve 0.5 A cm-2 in a continuous-flow electrolyzer system along with excellent stability. In situ spectroscopic analysis reveals that the strong interfacial coordination in Ru@MnO2-x balances the competitive adsorption of glycerol and OH* on the catalyst surface. Theoretical calculations further demonstrate that the defect-rich MnO2 support promotes the dissociation of H2 O, while the defect-regulated Ru sites promote deprotonation and hydrogen desorption, synergistically enhancing glycerol-assisted hydrogen production.

Construction of urchin-like bimetallic phosphides induced by carbon dots for efficient wide pH hydrogen production

The development of an efficient noble-metal-free and pH-universal electrocatalyst for the hydrogen evolution reaction (HER) would be highly significant for hydrogen (H2) production via electrocatalytic water splitting. However, developing such a catalyst remains a formidable task. Herein, a strategy is proposed for the in situ fabrication of a novel urchin-like NiCoP microsphere catalyst (0.5CDs-NiCoP/NF) on nickel foam (NF) using carbon dots (CDs) as a directing agent. The strong bonding between the CDs and metals provides additional active sites, giving 0.5CDs-NiCoP/NF excellent electrocatalytic hydrogen evolution performance in environments ranging from acidic to basic. Moreover, the unique structure of 0.5CDs-NiCoP/NF endows this catalyst with low Tafel slopes of 73, 146 and 74 mV dec-1 for HER in acidic, neutral and alkaline conditions, respectively. This performance exceeds that of numerous other reported non-precious HER catalysts. In summary, this work offers a novel and efficient strategy for the design and synthesis of low-cost, efficient, and robust transition metal phosphides (TMPs) electrocatalysts.

Microwave Phosphine-Plasma-Assisted Ultrafast Synthesis of Halogen-Doped Ru/RuP2 with Surface Intermediate Adsorption Modulation for Efficient Alkaline Hydrogen Evolution Reaction

Anionic modification engineering is a crucial approach to develop highly efficient electrocatalysts for hydrogen evolution reaction. Herein, halogen elements (X = Cl, Br, and I)-modified Ru-based nanosheets (X-Ru/RuP2 ) are designed by rapid and eco-friendly microwave-phosphide plasma approach within 60 s. Experimental and density functional theory calculations verify that the introduced halogen element, especially Br, can optimize the surface intermediates adsorption. Specially, the designed Br-Ru/RuP2 favors the water dissociation and following hydrogen adsorption/desorption process. Then, the as-synthesized Br-Ru/RuP2 exhibits low overpotential of 34 mV to reach 10 mA cm-2 coupled with small Tafel slope of 27 mV dec-1 in alkaline electrolyte with excellent long-term stability. Moreover, the electrocatalytic performances in acid and neutral media are also boosted via Br element modification. This work paves a novel way to regulate the electronic structure of Ru-based compounds, and then can boost the electrocatalytic kinetics.

Confinement Engineering of Zinc Single-Atom Triggered Charge Redistribution on Ruthenium Site for Alkaline Hydrogen Production

Optimizing the interaction between metal and support in the supported metal catalysts effectively refines the electronic structure and boosts the catalytic properties of loaded active components. Herein a method is introduced to confine ultrafine ruthenium (Ru) nanoparticles within atomically dispersed Zn-N4 sites on a N-doped carbon network (Ru/Zn-N-C) through the strong electronic metal-support interaction, achieving superior catalytic activity and stability for alkaline hydrogen evolution. Spectroscopic data and theoretical modeling elucidate that the remarkable catalytic performance of Ru sites stems from their strong electronic coupling with neighboring Zn-N4 moiety and pyridinic N/pyrrolic N. This interaction induces an electron-deficient state of Ru, thereby accelerating the dissociation of H2 O and lowering the energy barriers for the desorption of OH* and H*. This insight provides a deeper understanding of the catalytic mechanisms at play. Furthermore, alkaline water electrolyzer using this catalyst as cathode delivers a mass activity of 3 A mgcat -1 at 2.0 V, much surpassing Ru-C. This research opens a novel pathway for the development of advanced materials , tailored for energy storage and conversion applications.

Carbonized Polymer Dots/Bi/β-Bi2O3 for Efficient Photosynthesis of H2O2 via Redox Dual Pathways

A novel heterojunction photocatalyst of carbonized polymer dots (CPDs)/Bi/β-Bi2O3 is successfully synthesized via a one-pot solvothermal method by adjusting the reaction temperature and time. As a solvent and carbon source, ethylene glycol not only supports the conversion of Bi3+ to β-Bi2O3 but also undergoes its polymerization, cross-linking, and carbonization to produce CPDs. In addition, partial Bi3+ is reduced to Bi by ethylene glycol. As a result, the CPDs and Bi are deposited in situ on the surface of β-Bi2O3 microspheres. There are four built-in electric fields in the CPDs/Bi/β-Bi2O3 system, namely, the n-type semiconductor β-Bi2O3/H2O interface, the p-type CPDs/H2O interface, the ohmic contact between Bi and β-Bi2O3, and the Schottky junction between Bi and CPDs. Under the action of four built-in electric fields, the Z-type charge separation mechanism is formed. It promotes the effective separation of the photogenerated electron-hole and greatly improves the yield of H2O2. Under irradiation for 2 h, the H2O2 production is 1590 μmol g-1 h-1. The solar energy to H2O2 conversion efficiency is 0.11%.

Optimizing Pt-Based Alloy Electrocatalysts for Improved Hydrogen Evolution Performance in Alkaline Electrolytes: A Comprehensive Review

The splitting of water through electrocatalysis offers a sustainable method for the production of hydrogen. In alkaline electrolytes, the lack of protons forces water dissociation to occur before the hydrogen evolution reaction (HER). While pure Pt is the gold standard electrocatalyst in acidic electrolytes, since the 5d orbital in Pt is nearly fully occupied, when it overlaps with the molecular orbital of water, it generates a Pauli repulsion. As a result, the formation of a Pt-H* bond in an alkaline environment is difficult, which slows the HER and negates the benefits of using a pure Pt catalyst. To overcome this limitation, Pt can be alloyed with transition metals, such as Fe, Co, and Ni. This approach has the potential not only to enhance the performance but also to increase the Pt dispersion and decrease its usage, thus overall improving the catalyst's cost-effectiveness. The excellent water adsorption and dissociation ability of transition metals contributes to the generation of a proton-rich local environment near the Pt-based alloy that promotes HER. Significant progress has been achieved in comprehending the alkaline HER mechanism through the manipulation of the structure and composition of electrocatalysts based on the Pt alloy. The objective of this review is to analyze and condense the latest developments in the production of Pt-based alloy electrocatalysts for alkaline HER. It focuses on the modified performance of Pt-based alloys and clarifies the design principles and catalytic mechanism of the catalysts from both an experimental and theoretical perspective. This review also highlights some of the difficulties encountered during the HER and the opportunities for increasing the HER performance. Finally, guidance for the development of more efficient Pt-based alloy electrocatalysts is provided.

Facile Synthesis and Multiple Application of Ultralong-Afterglow Room Temperature Phosphorescence Aggregate Carbon Dots from Simple Raw Materials

Owing to the ultralong afterglow, room temperature decay phosphorescence nanomaterials have aroused enough attention. In the work, by simple one-pot solid-state thermal decomposition reaction, aggregate carbon dots (CDs) was prepared from trimesic and boric acid. Based on the intermolecular hydrogen bonds and intramolecular π-π stacking weak interaction from precursors, CDs was encapsulated in boron oxide matrix and formed aggregation. The aggregate state of CDs facilitated the triplet excited states (Tn), which could induce the room temperature decay phosphorescence properties. By careful investigation, under different excitation wavelengths at 254 and 365 nm, the aggregate CDs showed > 15 s and > 3 s room temperature phosphorescence emission in the naked eye, which was associated with 1516.12 ms and 718.62 ms lifetime respectively. And the aggregate CDs exhibited widespread application in encoding encryption, optical anti-counterfeiting and fingerprint identification etc. The interesting aggregate CDs revealed unexpected ultralong-afterglow room temperature decay phosphorescence properties and the work opened a window for constructing ultralong-afterglow room temperature decay phosphorescence aggregate CDs nanomaterials.

DFT-assisted low-dimensional carbon-based electrocatalysts design and mechanism study: a review

Low-dimensional carbon-based (LDC) materials have attracted extensive research attention in electrocatalysis because of their unique advantages such as structural diversity, low cost, and chemical tolerance. They have been widely used in a broad range of electrochemical reactions to relieve environmental pollution and energy crisis. Typical examples include hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR). Traditional "trial and error" strategies greatly slowed down the rational design of electrocatalysts for these important applications. Recent studies show that the combination of density functional theory (DFT) calculations and experimental research is capable of accurately predicting the structures of electrocatalysts, thus revealing the catalytic mechanisms. Herein, current well-recognized collaboration methods of theory and practice are reviewed. The commonly used calculation methods and the basic functionals are briefly summarized. Special attention is paid to descriptors that are widely accepted as a bridge linking the structure and activity and the breakthroughs for high-volume accurate prediction of electrocatalysts. Importantly, correlated multiple descriptors are used to systematically describe the complicated interfacial electrocatalytic processes of LDC catalysts. Furthermore, machine learning and high-throughput simulations are crucial in assisting the discovery of new multiple descriptors and reaction mechanisms. This review will guide the further development of LDC electrocatalysts for extended applications from the aspect of DFT computations.

Biomass-Derived Carbon-Based Multicomponent Integration Catalysts for Electrochemical Water Splitting

Electrocatalytic water splitting powered by sustainable electricity is a crucial approach for the development of new generation green hydrogen technology. Biomass materials are abundant and renewable, and the application of catalysis can increase the value of some biomass waste and turn waste into fortune. Converting economical and resource-rich biomass into carbon-based multicomponent integrated catalysts (MICs) has been considered as one of the most promising ways to obtain inexpensive, renewable and sustainable electrocatalysts in recent years. In this review, recent advances in biomass-derived carbon-based MICs towards electrocatalytic water splitting are summarized, and the existing issues and key aspects in the development of these electrocatalysts are also discussed and prospected. The application of biomass-derived carbon-based materials will bring some new opportunities in the fields of energy, environment, and catalysis, as well as promote the commercialization of new nanocatalysts in the near future.

Revealing the role of interfacial water and key intermediates at ruthenium surfaces in the alkaline hydrogen evolution reaction

Ruthenium exhibits comparable or even better alkaline hydrogen evolution reaction activity than platinum, however, the mechanistic aspects are yet to be settled, which are elucidated by combining in situ Raman spectroscopy and theoretical calculations herein. We simultaneously capture dynamic spectral evidence of Ru surfaces, interfacial water, *H and *OH intermediates. Ru surfaces exist in different valence states in the reaction potential range, dissociating interfacial water differently and generating two distinct *H, resulting in different activities. The local cation tuning effect of hydrated Na+ ion water and the large work function of high-valence Ru(n+) surfaces promote interfacial water dissociation. Moreover, compared to low-valence Ru(0) surfaces, high-valence Ru(n+) surfaces have more moderate adsorption energies for interfacial water, *H, and *OH. They, therefore, facilitate the activity. Our findings demonstrate the regulation of valence state on interfacial water, intermediates, and finally the catalytic activity, which provide guidelines for the rational design of high-efficiency catalysts.

Design of carbon dots for bioimaging and behavior regulation of stem cells

Carbon dots (CDs) have been widely used in bioimaging, biosensing and biotherapy because of their good biocompatibility, optical properties and stability. In this review, we comprehensively summarize the research on CDs in terms of synthesis methods, optical properties and biotoxicity. We describe and envisage the directions for CDs application in stem cell imaging and differentiation, with the aim of stimulating the design of future related CDs. We used 'carbon dots', 'stem cells', 'cell imaging', 'cell differentiation' and 'fate control' as keywords to search for important articles. The Web of Science database was used to extract vital information from a total of 357 papers, 126 review articles and 231 article proceedings within 12 years (2011-2022).

Co@Co Cages Engineered from Hollowing MOFs for Enhanced Hydrogen Evolution Reaction Performance

Advances in hollow engineering of metal-organic frameworks (MOFs) have enabled a variety of applications in catalysts, sensors, and batteries, but the hollow derivatives are often limited to hydroxides, oxides, selenides, and sulfides with the presence of additional elements from the environment. Here we have successfully synthesized hollow metallic Co@Co cages through a facile two-step strategy. Interestingly, the Co@Co(C) cages with a small amount of residual carbon show excellent catalytic performance due to the abundant exposed active sites and fast charge transfer. During the hydrogen evolution reaction, the overpotential of Co@Co(C) is as low as ∼54 mV at the current density of 10 mA cm^-2, which is close to that of ∼38 mV for the Pt/C electrodes. The two-step synthesis strategy opens up opportunities for increasing the number of catalytic active sites and rates of charge/mass transfer while pushing the limits of materials utilization beyond that achieved in existing MOF-based nanostructures.

Ni3S2/Co9S8 embedded poor crystallinity NiCo layered double hydroxides hierarchical nanostructures for efficient overall water splitting

Nickel-cobalt bimetallic layered double hydroxides (NiCo LDHs) are potential electrocatalysts with high performance and stability for overall water-splitting. However, its weak conductivity limits its practical applications. Herein, a simple hydrothermal in-situ conversion strategy is employed for constructing the novel heterogeneous electrocatalyst of Ni₃S₂/Co₉S₈ embedded poor crystallinity (Pc) NiCo LDH nanosheet arrays grown on the Ni foam (Pc-NiCo LDH/ Ni₃S₂/Co₉S₈), which can improve the conductivity via regulating the crystallinity. The crystallinity of NiCo LDH is well regulated by adjusting the amount of sulfur source, and the construction of Ni₃S₂/Co₉S₈ heterostructure exposes more active sites, improves the electrical conductivity, enhances the electronic interaction between NiCo LDH and Ni₃S₂/Co₉S₈, and significantly promotes the kinetics of water splitting. The optimized Pc-NiCo LDH/Ni₃S₂/Co₉S₈ hierarchical structure as both the anode and cathode exhibit the overall water splitting performance with the cell voltage of only 1.744 V to achieve the current density of 50 mA cm^-2 in the alkaline media and shows the competitive H₂ and O₂ production rate of 6.4 and 3.1 μL s^-1, respectively, suggesting its potential practical applications. This work provides a novel idea for the design of multiphase composite electrocatalysts applied in water splitting.

Progress in electrocatalytic hydrogen evolution of transition metal alloys: synthesis, structure, and mechanism analysis

At present, the problems of high energy consumption and low efficiency in electrocatalytic hydrogen production have limited the large-scale industrial application of this technology. Constructing effective catalysts has become the way to solve these problems. Transition metal alloys have been proved to be very promising materials in hydrogen evaluation reaction (HER). In this study, the related theories and characterization methods of electrocatalysis are summarized, and the latest progress in the application of binary, ternary, and high entropy alloys to HER in recent years is analyzed and studied. The synthesis methods and optimization strategies of transition metal alloys, including composition regulation, hybrid engineering, phase engineering, and morphological engineering were emphatically discussed, and the principles and performance mechanism analysis of these strategies were discussed in detail. Although great progress has been made in alloy catalysts, there is still considerable room for applications. Finally, the challenges, prospects, and research directions of transition metal alloys in the future were predicted.

Dispersing small Ru nanoparticles into boron nitride remodified by reduced graphene oxide for high-efficient electrocatalytic hydrogen evolution reaction

Ruthenium (Ru) electrocatalysts suffer from excessive aggregation during the hydrogen evolution reaction (HER), which hinders their practical application for hydrogen production. Hexagonal boron nitride (h-BN) is a potential carrier that could solve the above problem, but its wide band gap and low conductivity become obstacles. Herein, we provide a new, facile, low-cost, and effective strategy (killing two birds with one stone) to overcome the above issues. After modifying h-BN with reduced graphene oxide (rGO), a small amount of Ru nanoparticles (NPs) (2.2 %) are dispersed into BN with approximately uniform distribution and size control of Ru nanoparticles (∼3.85 nm). The strong synergy between Ru NPs and BN@C in the optimal Ru/BN@C (Ru wt.% = 2.22 %) electrocatalyst endows it an outstanding HER activity, with small HER overpotentials (η₁₀ = 32 mV, 35 mV) and low Tafel slopes (33.89 mV dec^-1, 37.66 mV dec^-1) in both 1 M KOH and 0.5 M H₂SO₄ media, respectively, along with good long-term stability for 50 h. Based on density functional theory (DFT) calculations, the addition of Ru to BN has been successful in creating fresh active sites for H*, with good possible adsorption/desorption ability (ΔG_H* = -0.24 eV) while preserving low water dissociation (ΔG_b = 0.46 eV) in an alkaline environment. As a result, the Ru/BN composite exhibits outstanding HER activity in both acidic and alkaline conditions. Furthermore, this study provides, for the first time, a template-free strategy to develop a good and low-cost supporter (BN) for dispersing other noble metals and the formation of highly efficient HER/OER electrocatalysts.

Diethylenetriamine-β-CD-modified carbon quantum dots for selective fluorescence sensing of Hg2+ and Fe3+ and cellular imaging

Diethylenetriamine-β-cyclodextrin-modified carbon quantum dots (3 N-CQDs) were synthesized via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin (3 N-β-CD) as the nitrogen source. The successful preparation of 3 N-CQDs were revealed by infrared absorption spectroscopy, ultraviolet (UV)-visible absorption spectroscopy, fluorescence spectroscopy, XRD, XPS, TEM, and TG. Further spectroscopic studies showed that the synthesized carbon quantum dots offered good anti-interference capability. The relative fluorescence quantum yield was 67.2 %. The limits of detection for Hg²⁺ and Fe³⁺ were 0.25 µM and 0.57 μM, respectively. Cytotoxicity and imaging studies showed that the prepared carbon quantum dots had low cytotoxicity, good biocompatibility, and good cellular imaging capability for HeLa cells. They offered fluorescent sensing of Hg²⁺ and Fe³⁺ in live cells. Therefore, 3 N-CQDs were ideal fluorescent probes for the detection of Hg²⁺ and Fe³⁺ in water.

Emerging Trends of Carbon-Based Quantum Dots: Nanoarchitectonics and Applications

Carbon-based quantum dots (QDs) have emerged as a fascinating class of advanced materials with a unique combination of optoelectronic, biocompatible, and catalytic characteristics, apt for a plethora of applications ranging from electronic to photoelectrochemical devices. Recent research works have established carbon-based QDs for those frontline applications through improvements in materials design, processing, and device stability. This review broadly presents the recent progress in the synthesis of carbon-based QDs, including carbon QDs, graphene QDs, graphitic carbon nitride QDs and their heterostructures, as well as their salient applications. The synthesis methods of carbon-based QDs are first introduced, followed by an extensive discussion of the dependence of the device performance on the intrinsic properties and nanostructures of carbon-based QDs, aiming to present the general strategies for device designing with optimal performance. Furthermore, diverse applications of carbon-based QDs are presented, with an emphasis on the relationship between band alignment, charge transfer, and performance improvement. Among the applications discussed in this review, much focus is given to photo and electrocatalytic, energy storage and conversion, and bioapplications, which pose a grand challenge for rational materials and device designs. Finally, a summary is presented, and existing challenges and future directions are elaborated.

A Double Atomic-Tuned RuBi SAA/Bi@OG Nanostructure with Optimum Charge Redistribution for Efficient Hydrogen Evolution

Charge redistribution on surface of Ru nanoparticle can significantly affect electrocatalytic HER activity. Herein, a double atomic-tuned RuBi SAA/Bi@OG nanostructure that features RuBi single-atom alloy nanoparticle supported by Bi-O single-site-doped graphene was successfully developed by one-step pyrolysis method. The alloyed Bi single atom and adjacent Bi-O single site in RuBi SAA/Bi@OG can synergistically manipulate electron transfer on Ru surface leading to optimum charge redistribution. Thus, the resulting RuBi SAA/Bi@OG exhibits superior alkaline HER activity. Its mass activity is up to 65000 mA mg^-1 at an overpotential of 150 mV, which is 72.2 times as much as that of commercial Pt/C. DFT calculations reveal that the RuBi SAA/Bi@OG possesses the optimum charge redistribution, which is most beneficial to strengthen adsorption of water and weaken hydrogen-adsorption free energy in HER process. This double atomic-tuned strategy on surface charge redistribution of Ru nanoparticle opens a new way to develop highly efficient electrocatalysts.

Tailored nitrogen-defect induced by diels-alder reaction for enhanced electrochemical hydrogen evolution reaction

Electrocatalytic water splitting in an alkaline medium is recognized as the promising technology to sustainably generate clean hydrogen energy via hydrogen evolution reaction (HER), while the sluggish water dissociation and subsequent *H adsorption steps greatly retarded the reaction kinetics and efficiency of the overall hydrogen evolution process. Whilst nitrogen (N)-doped carbon-based materials are attractive candidates for promoting HER activity, the facile fabrication and gaining a deeper insight into the electrocatalytic mechanism are still challenging. Herein, inspired by the Diels-Alder reaction, we precisely tailored six-membered pyridinic N and five-membered pyrrolic N sites at the edge of the carbon substrates. Comprehensive analysis validates that the participation of pyridinic N (electron-withdrawing) and pyrrolic N (electron-releasing) will induce the charge rearrangements, and further generate local electrophilic and nucleophilic domains in adjacent carbon rings, which guarantees the occurrence of water dissociation to generate protons and the subsequent adsorption of *H intermediates through electrostatic interactions, thereby facilitating the overall reaction kinetics. To this end, the optimal NC-ZnCl₂-25 % electrocatalysts present excellent alkaline HER activity (η₁₀ = 45 mV, Tafel slop of 37.7 mV dec^-1) superior to commercial Pt/C.

Strategies for Promoting Catalytic Performance of Ru-based Electrocatalysts towards Oxygen/Hydrogen Evolution Reaction

Ru-based materials hold great promise for substituting Pt as potential electrocatalysts toward water electrolysis. Significant progress is made in the fabrication of advanced Ru-based electrocatalysts, but an in-depth understanding of the engineering methods and induced effects is still in their early stage. Herein, we organize a review that focusing on the engineering strategies toward the substantial improvement in electrocatalytic OER and HER performance of Ru-based catalysts, including geometric structure, interface, phase, electronic structure, size, and multicomponent engineering. Subsequently, the induced enhancement in catalytic performance by these engineering strategies are also elucidated. Furthermore, some representative Ru-based electrocatalysts for the electrocatalytic HER and OER applications are also well presented. Finally, the challenges and prospects are also elaborated for the future synthesis of more effective Ru-based catalysts and boost their future application.

Full-Color Circularly Polarized Luminescence of CsPbX3 Nanocrystals Triggered by Chiral Carbon Dots

Chiral carbon dots (Ch-CDs) trigger the full-color circularly polarized luminescence (CPL) of CsPbX₃  nanocrystals (NCs). Ch-CDs-CsPbBr₃  NCs are successfully synthesized via simple ligand-assisted coprecipitation of Ch-CDs and metal halides precursors at room temperature. Ch-CDs-CsPbBr₃  retains emission characteristics of the CsPbBr₃  with near-unity photoluminescence quantum yield, and meanwhile has special CPL, with a maximum luminescence dissymmetric factor (g_lum ) of -3.1 × 10^-3 , which is induced by Ch-CDs. This is the first report of chiral perovskite which is induced by other chiral nanomaterials. By anion exchange, CPL can cover almost the entire visible light band. Surprisingly, the chiral signal of Ch-CDs-CsPbBr₃  NCs is in-versed under excitation state, which can be induced by the charge transfers between Ch-CDs and perovskite NCs. The combination of perovskites and Ch-CDs pave away for the design of new chiral perovskite on multifunctional applications.

Self-assembled ZnO microspheres coated with carbon dot-doped CoNi LDH wrinkled films as electrochemical sensors for highly sensitive detection of hydrazine

In this study, a 3D surface-folded composite was prepared in situ as a hydrazine sensor by loading a hybrid film of CoNi-layered double hydroxides (LDHs) with nitrogen-doped carbon dots on self-assembled ZnO microspheres. The nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), and the electrochemical behavior of the sensors was investigated by cyclic voltammetry (CV), amperometry and electrochemical impedance spectroscopy (EIS). The results showed that ZnO microspheres with nitrogen-doped carbon dots strongly coupled with LDHs can significantly reduce the charge transfer resistance, accelerate the oxidation kinetics of hydrazine, and effectively increase the electrochemically active surface area (ECSA). The sensor achieved ultra-sensitive (13 040 μA mM^-1 cm^-2 (S/N = 3)) detection of hydrazine in the concentration range of 0.7 μM to 4 mM, exhibited excellent selectivity, reproducibility and high stability, and was successfully applied to the determination of hydrazine in actual environmental water samples and landfill leachate samples.

Orbital Occupancy and Spin Polarization: From Mechanistic Study to Rational Design of Transition Metal-Based Electrocatalysts toward Energy Applications

Over the past few decades, development of electrocatalysts for energy applications has extensively transitioned from trial-and-error methodologies to more rational and directed designs at the atomic levels via either nanogeometric optimization or modulating electronic properties of active sites. Regarding the modulation of electronic properties, nonprecious transition metal-based materials have been attracting large interest due to the capability of versatile tuning d-electron configurations expressed through the flexible orbital occupancy and various possible degrees of spin polarization. Herein, recent advances in tailoring electronic properties of the transition-metal atoms for intrinsically enhanced electrocatalytic performances are reviewed. We start with discussions on how orbital occupancy and spin polarization can govern the essential atomic level processes, including the transport of electron charge and spin in bulk, reactive species adsorption on the catalytic surface, and the electron transfer between catalytic centers and adsorbed species as well as reaction mechanisms. Subsequently, different techniques currently adopted in tuning electronic structures are discussed with particular emphasis on theoretical rationale and recent practical achievements. We also highlight the promises of the recently established computational design approaches in developing electrocatalysts for energy applications. Lastly, the discussion is concluded with perspectives on current challenges and future opportunities. We hope this review will present the beauty of the structure-activity relationships in catalysis sciences and contribute to advance the rational development of electrocatalysts for energy conversion applications.

Bioresource-Functionalized Quantum Dots for Energy Generation and Storage: Recent Advances and Feature Perspective

The exponential increase in global energy demand in daily life prompts us to search for a bioresource for energy production and storage. Therefore, in developing countries with large populations, there is a need for alternative energy resources to compensate for the energy deficit in an environmentally friendly way and to be independent in their energy demands. The objective of this review article is to compile and evaluate the progress in the development of quantum dots (QDs) for energy generation and storage. Therefore, this article discusses the energy scenario by presenting the basic concepts and advances of various solar cells, providing an overview of energy storage systems (supercapacitors and batteries), and highlighting the research progress to date and future opportunities. This exploratory study will examine the systematic and sequential advances in all three generations of solar cells, namely perovskite solar cells, dye-sensitized solar cells, Si cells, and thin-film solar cells. The discussion will focus on the development of novel QDs that are economical, efficient, and stable. In addition, the current status of high-performance devices for each technology will be discussed in detail. Finally, the prospects, opportunities for improvement, and future trends in the development of cost-effective and efficient QDs for solar cells and storage from biological resources will be highlighted.

Tea-polyphenol green fabricating catkin-like CuAg for electrochemical H2O2 detection

Green fabrication of unique structural nanoparticles has always been of increasing interest in many fields. Herein, a facile and green strategy of fabricating catkin-like CuAg nanocomposites using tea-polyphenols as reduction agent is reported. As-prepared nanocomposites have been characterized by a series of analysis. Physical characterizations show the synthesised of nanocomposites whose catkin-like special morphology. The electrochemical detection hydrogen peroxide (H2O2) results show that, catkin-like CuAg nanocomposites have good sensitivity, stability and anti-interference and it could detect without any additional mediator or enzyme. Specifically, it shows good H2O2 sensitivity of 2.55 μA mM-1cm-2 with range of 0.1-120 mM. Therefore, the catkin-like CuAg nanocomposites prepared by an environmental-friendly synthetic strategy, would provide a good reference for other green syntheses in the future.

N-Doped sp2 /sp3 Carbon Derived from Carbon Dots to Boost the Performance of Ruthenium for Efficient Hydrogen Evolution Reaction

The structure and properties of the carrier significantly affect the catalytic activity of the active centers for supported electrocatalysts. Therefore, elaborate design and regulation of the physicochemical properties of carbon carriers are essential to improve the activity and stability of the carbon-supported ruthenium-based catalysts. Herein, enlightened by the unique characteristics of coexisting sp² and sp³ carbon nuclei in N-doped carbon dots (NCDs), a hybrid structure of N-doped carbon substrates featuring N-doped sp² /sp³ carbon interfaces loaded with Ru nanoparticles (Ru/NCDs) is obtained. Spectroscopic analysis and density functional theory calculations illustrate that the interaction between Ru and NCDs effectively modulates the electronic structure of the active center Ru, and the formed N-doped sp² /sp³ carbon interface lowers the energy barrier of the intermediates in hydrogen evolution reaction (HER) and balances the hydrogen adsorption and desorption and, thereby, greatly improves the activity of Ru/NCDs. Remarkably, Ru/NCDs exhibit excellent HER activity and stability in comparison to Pt/C, which merely requires overpotentials as low as 37 and 14 mV at 10 mA cm^-2 in alkaline and acidic electrolytes, respectively. This finding will provide more thoughts about the influence of substrate properties on the catalytic activity and rational design of carbon-loaded electrocatalysts.

Influence of Nitrogen-Doped Carbon Quantum Dots on the Electrocatalytic Performance of the CoP Nanoflower Catalyst for OER

Cobalt phosphides modified by nitrogen-doped carbon quantum dots (CoP-NCQDs) were successfully constructed by a facile and low-cost hydrothermal treatment, which is expected to replace traditional noble-metal oxygen evolution reaction electrode materials. Detailed experiments and findings show that nitrogen-doped carbon quantum dots (NCQDs) have a significant impact on the morphology of the CoP catalyst, and nitrogen doping can regulate the surface-active sites to obtain the catalyst with abundant structural defects. Simultaneously, nitrogen doping can regulate the content of pyridinic N and pyrrolic N, which exerts positive effects on the formation of the bond structure and electron conduction between NCQDs and CoP.

Controlled growth of a high selectivity interface for seawater electrolysis

Overall seawater electrolysis is an important direction for the development of hydrogen energy conversion. The key issues include how to achieve high selectivity, activity, and stability in seawater electrolysis reactions. In this report, the heterostructures of graphdiyne-RhO_x-graphdiyne (GDY/RhO_x/GDY) were constructed by in situ-controlled growth of GDY on RhO_x nanocrystals. A double layer interface of sp-hybridized carbon-oxide-Rhodium (sp-C∼O-Rh) was formed in this system. The microstructures at the interface are composed of active sites of sp-C∼O-Rh. The obvious electron-withdrawing surface enhances the catalytic activity with orders of magnitude, while the GDY outer of the metal oxides guarantees the stability. The electron-donating and withdrawing sp-C∼O-Rh structures enhance the catalytic activity, achieving high-performance overall seawater electrolysis with very small cell voltages of 1.42 and 1.52 V at large current densities of 10 and 500 mA cm^-2 at room temperatures and ambient pressures, respectively. The compositional and structural superiority of the GDY-derived sp-C-metal-oxide active center offers great opportunities to engineer tunable redox properties and catalytic performance for seawater electrolysis and beyond. This is a typical successful example of the rational design of catalytic systems.

Rhodium nanocrystals on porous graphdiyne for electrocatalytic hydrogen evolution from saline water

The realization of the efficient hydrogen conversion with large current densities at low overpotentials represents the development trend of this field. Here we report the atomic active sites tailoring through a facile synthetic method to yield well-defined Rhodium nanocrystals in aqueous solution using formic acid as the reducing agent and graphdiyne as the stabilizing support. High-resolution high-angle annular dark-field scanning-transmission electron microscopy images show the high-density atomic steps on the faces of hexahedral Rh nanocrystals. Experimental results reveal the formation of stable sp-C~Rh bonds can stabilize Rh nanocrystals and further improve charge transfer ability in the system. Experimental and density functional theory calculation results solidly demonstrate the exposed high active stepped surfaces and various metal atomic sites affect the electronic structure of the catalyst to reduce the overpotential resulting in the large-current hydrogen production from saline water. This exciting result demonstrates unmatched electrocatalytic performance and highly stable saline water electrolysis.

A Review on Carbon Dots: Synthesis, Characterization and Its Application in Optical Sensor for Environmental Monitoring

The development of carbon dots (CDs), either using green or chemical precursors, has inevitably led to their wide range application, from bioimaging to optoelectronic devices. The reported precursors and properties of these CDs have opened new opportunities for the future development of high-quality CDs and applications. Green precursors were classified into fruits, vegetables, flowers, leaves, seeds, stem, crop residues, fungi/bacteria species, and waste products, while the chemical precursors were classified into acid reagents and non-acid reagents. This paper quickly reviews ten years of the synthesis of CDs using green and chemical precursors. The application of CDs as sensing materials in optical sensor techniques for environmental monitoring, including the detection of heavy metal ions, phenol, pesticides, and nitroaromatic explosives, was also discussed in this review. This profound review will offer knowledge for the upcoming community of researchers interested in synthesizing high-quality CDs for various applications.