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Band gap opening and engineering make up one of the primary goals of developing novel materials for photocatalytic hydrogen generation. We report here a facile synthesis of graphene decorated with in-plane boron nitride domains via control of both the doping sequence of heteroatoms and the oxygen content of the graphene precursor, showing significant differences in the doping pattern compared with B and/or N singly doped or co-doped graphene. We uncover that the formation of BN domains in graphene is critical for engineering the band gap and delivering an improved activity for photocatalytic hydrogen generation in the absence of any photosensitizer. This work paves the way for the rational design and construction of graphene-based photocatalysts for efficient photocatalysis.

This paper briefly introduces the optimal threshold calculation model and particle swarm optimization (PSO) algorithm for image segmentation and improves the PSO algorithm. Then the standard PSO algorithm and improved PSO algorithm were used in MATLAB software to make simulation analysis on image segmentation. The results show that the improved PSO algorithm converges faster and has higher fitness value; after the calculation of the two algorithms, it is found that the improved PSO algorithm is better in the subjective perspective, and the image obtained by the improved PSO segmentation has higher regional consistency and takes shorter time in the perspective of quantitative objective data. In conclusion, the improved PSO algorithm is effective in image segmentation.

Solar-driven catalysis is a promising strategy for transforming CO2 into fuels and valuable chemical feedstocks, with current research focusing primarily on increasing CO2 conversion efficiency and product selectivity. Herein, a series of FeO–CeO2 nanocomposite catalysts were successfully prepared by H2 reduction of Fe(OH)3-Ce(OH)3 precursors at temperatures (x) ranging from 200 to 600 °C (the obtained catalysts are denoted as FeCe-x). An FeCe-300 catalyst with an Fe:Ce molar ratio of 2:1 demonstrated outstanding performance for photothermal CO2 conversion to CO in the presence of H2 under Xe lamp irradiation (CO2 conversion, 43.63%; CO selectivity, 99.87%; CO production rate, 19.61 mmol h−1 gcat−1; stable operation over 50 h). Characterization studies using powder X-ray diffraction and high-resolution transmission electron microscopy determined that the active catalyst comprises FeO and CeO2 nanoparticles. The selectivity to CO of the FeCe-x catalysts decreased as the reduction temperature (x) increased in the range of 300–500 °C due to the appearance of metallic Fe0, which introduced an additional reaction pathway for the production of CH4. In situ diffuse reflectance infrared Fourier transform spectroscopy identified formate, bicarbonate and methanol as important reaction intermediates during light-driven CO2 hydrogenation over the FeCe-x catalysts, providing key mechanistic information needed to explain the product distributions of CO2 hydrogenation on the different catalysts. A nanomaterial that helps convert carbon dioxide to more useful chemicals has been developed by researchers in China. One potential method is to convert the carbon dioxide into carbon monoxide using a reaction known as reverse water-gas shift, and then use further reactions to convert this into fuel, or produce useful chemicals such as methanol or methane. This reaction normally requires high temperatures, and a catalyst is required to make the conversion efficient at lower, more practical temperatures. Tierui Zhang from the Technical Institute of Physics and Chemistry in Beijing and co-workers developed a nanocomposite based on iron and cerium with excellent performance in converting carbon dioxide into carbon monoxide with hydrogen only under light irradiation. This result indicates the potential of solar-driven catalysis for transforming carbon dioxide into fuels. A series of FeO-CeO2 nanocomposite catalysts (FeCe-x) were successfully fabricated by hydrogen reduction of hydroxide precursors at temperatures (x) between 200–600 °C. A FeCe-300 catalyst with a Fe:Ce ratio of 2-1 exhibited excellent performance for photothermal CO2 hydrogenation to CO (CO selectivity = 99.87%, CO production rate 19.61 mmol h−1 gcat−1, excellent stability). The FeO phase was effective in promoting the reverse water-gas shift (RWGS, CO2 + H2 → CO + H2O). Catalysts prepared at higher reduction temperatures contained both Fe0 and FeO, with the Fe0 catalyzing the Sabatier reaction (CO2 + 4H2 → CH4 + 2H2O) and thus lowering FeCe-x catalyst selectivity to CO.

Prompt recombination of photogenerated electrons and holes in bulk and on the surface of photocatalysts harshly impedes the photocatalytic efficiency. However, the simultaneous manipulation of photocharges in the two locations is challenging. Herein, the synchronous promotion of bulk and surface separation of photoinduced charges for prominent CO

With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible-light-driven splitting of water into hydrogen and oxygen using semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light-absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible-light-driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self-assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed.

The development of efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) is critical for the large-scale production of fuel cells. Platinum (Pt) nanoparticle catalysts show excellent performance for ORR, though the high cost of Pt is a limiting factor that directly impacts fuel cell production costs. Alloying Pt with other transition metals is an effective strategy to reduce Pt utilization whilst maintaining good ORR performance. In this work, novel hollow PtFe alloy catalysts were successfully synthesized by high-temperature pyrolysis of SiO

There is interest in metal single atom catalysts due to their remarkable activity and stability. However, the synthesis of metal single atom catalysts remains somewhat ad hoc, with no universal strategy yet reported that allows their generic synthesis. Herein, we report a universal synthetic strategy that allows the synthesis of transition metal single atom catalysts containing Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pt or combinations thereof. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and extended X-ray absorption fine structure spectroscopy confirm that the transition metal atoms are uniformly dispersed over a carbon black support. The introduced synthetic method allows the production of carbon-supported metal single atom catalysts in large quantities (>1 kg scale) with high metal loadings. A Ni single atom catalyst exhibits outstanding activity for electrochemical reduction of carbon dioxide to carbon monoxide, achieving a 98.9% Faradaic efficiency at −1.2 V., Single-atom catalysts are a promising class of catalytic materials, but general synthetic methods are limited. Here, the authors develop a ligand-mediated strategy that allows the large-scale synthesis of diverse transition metal single atom catalysts supported on carbon.

Nanozymes have attracted extensive interest owing to their high stability, low cost and easy preparation, especially in the field of cancer therapy. However, the relatively low catalytic activity of nanozymes in the tumor microenvironment (TME) has limited their applications. Herein, we report a novel nanozyme (PtFe@Fe3 O4 ) with dual enzyme-like activities for highly efficient tumor catalytic therapy. PtFe@Fe3 O4 shows the intrinsic photothermal effect as well as photo-enhanced peroxidase-like and catalase-like activities in the acidic TME, thereby effectively killing tumor cells and overcoming the tumor hypoxia. Importantly, a possible photo-enhanced synergistic catalytic mechanism of PtFe@Fe3 O4 was first disclosed. We believe that this work will advance the development of nanozymes in tumor catalytic therapy.

Synthesizing nanomaterials with anisotropic architectures, especially two-dimensional (2D) nanosheets (NSs), is a key focus of materials science research. Metal sulfide nanosheets (MSNSs) are typically obtained involving exfoliation of bulk metal sulfides with layered structures. The synthesis of NSs of intrinsically non-layered metal sulfides has received relatively less attention. Metal alkanethiolates with lamellar structures are now shown to serve as effective scaffolds for constructing NSs. A novel photochemical step was employed to transform 2D metal thiolates into MSNSs. By this strategy the 2D nature of metal thiolate precursors was preserved in the final products, resulting in the successful synthesis of NSs of binary PbS, CdS, and Cu9 S5 , as well as ternary wurtzite CuInS2 , Cu2 SnS3 . Results encourage the wider utilization of photochemical strategies in the synthesis of anisotropic MSNSs.

Solar-driven Fischer-Tropsch synthesis (FTS) holds great potential for the sustainable production of fuels from syngas and solar energy. However, the selectivity toward multi-carbon products (C2+ ) is often hampered by the difficulty in the regulation of transition metals acting as both light absorption units and active sites. Herein, a partial phosphidation strategy to prepare titania supported Ni2 P/Ni catalysts for photothermal FTS is demonstrated. Under Xenon lamp or concentrated sunlight irradiation, the optimized catalyst shows a C2+ selectivity of 70% at a CO conversion of >20%. Conversely, nickel metal in the absence of Ni2 P delivers negligible C2+ products (≈1%) with methane being the major product (>90%). Structural characterization and density functional theory calculation reveal that the partial phosphidation allows exposed metallic Ni to be active for CO adsorption and activation, while the existence of Ni2 P/Ni interface is responsible to inhibit CO methanation and promote C-C coupling of adsorbed *CH intermediates. This work introduces a novel phosphidation strategy for nickel-based photothermal catalysts in efficiently harnessing solar energy, and regulating the reaction pathways for CO hydrogenation to deliver high value products.

Fe single-atom catalysts (Fe SACs) with atomic FeNx active sites are very promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR). The pyrolysis of metal-organic frameworks (MOFs) is a common approach for preparing Fe SACs, though most MOF-derived catalysts reported to date are microporous and thus suffer from poor mass transfer and a high proportion of catalytically inaccessible FeNx active sites. Herein, NH2 -MIL-101(Al), a MOF possessing a mesoporous cage architecture, is used as the precursor to prepare a series of N-doped carbon supports (denoted herein as NC-MIL101-T) with a well-defined mesoporous structure at different pyrolysis temperatures. The NC-MIL101-T supports are then impregnated with a Fe(II)-phenanthroline complex, and heated again to yield Fe SAC-MIL101-T catalysts rich in accessible FeNx single atom sites. The best performing Fe SAC-MIL101-1000 catalyst offers outstanding ORR activity in alkaline media, evidenced by an ORR half-wave potential of 0.94 V (vs RHE) in 0.1 m KOH, as well as excellent performance in both aqueous primary zinc-air batteries (a near maximum theoretical energy density of 984.2 Wh kgZn -1 ) and solid-state zinc-air batteries (a peak power density of 50.6 mW cm-2 and a specific capacity of 724.0 mAh kgZn -1 ).

Recently, heterogeneous photocatalysts have achieved much interest on account of their great potential applications in resolving many tough energy and environmental troubles around the world through an ecologically sustainable way. Heterogeneous nanocomposites composed of graphitic carbon nitride (g-C3 N4 ) and carbon dots (CDs) possess broad spectrum absorption, appropriate electronic band structures, rapid carrier mobility, abundant reserves, excellent chemical stability, and facile synthesis methods, which make them promising composite photocatalysts for suitable applications such as photocatalytic solar fuels production and contaminant decomposition. With the rapid development in photocatalysis by hybridization of g-C3 N4 and CDs, a systematic summary and prospection of performance improvement are urgent and meaningful. This review first focuses on various kinds of effectively synthetic methods of composites. Following, the strategies available for enhanced performance, including morphology optimization, spectral absorption improvement, ternary or quaternary composition hybrid, lateral or vertical heterostructures construction, heteroatom doping, and so forth, are fully discussed. Then, the applications mainly in efficient photocatalytic hydrogen generation, photocatalytic carbon dioxide reduction, and organic pollutants degradation are systematically demonstrated. Finally, the remaining issues and prospect of further development are proposed as some kind of guidance for powerful combination of g-C3 N4 and CDs with high efficiency to photocatalysis.

Summary The present study was conducted to evaluate the effects of different dietary chitosan oligosaccharide (COS) levels on digestive enzyme activity, intestinal bacteria flora, and growth performance of the tiger puffer (Takifugu rubripes). Some 600 fish (initial body weight 129.2 ± 3.1 g) were randomly allocated into twelve 2,000-L blue cylinder aquaria with 1,500-L of sea water and divided into four groups (n = 3 aquaria/diet). The fish were fed experimental diets supplemented with different levels of COS (0% [control, L1], 0.05% [LC1], 0.1% [LC2], and 0.2% [LC3]) for 8 weeks. During the experiment, the water temperature was 18 ± 1°C, salinity 28 ± 0.1, pH 8.0 ± 0.1 (mean ± SD, n = 672); airstones were positioned at the bottom of the tank, dissolved oxygen content was above 7.0 mg/L, with a photoperiod of 12 hr light: 12 hr dark. The results showed that dietary COS significantly increased growth performance, intestinal-somatic index (ISI), and intestinal protease as well as lipase activity (p .05). High-throughput sequencing analysis showed that COS affected the richness and diversity of intestinal microbial species. The Shannon index of intestinal bacterial flora was significantly higher in the control group than in other groups (p

Utilizing self-sacrificed transformation of the dual redox couples Ag/Ag+ and I−/(IO3)−, we developed a multiplex heterostructure Ag-AgI-AgIO3 by using a simple in-situ reduction strategy and AgIO3 as the sacrificed template. The reaction extent can be easily controlled via adjusting the reductant NaBH4 concentration. Benefiting from both Ag SPR and heterojunctional effects, the photoabsorption in the UV–vis region of Ag-AgI-AgIO3 is monotonously enhanced with increasing reductant concentration. The composite photocatalysts all exhibit highly enhanced photocatalytic activity in degrading methyl orange (MO) under both UV light and visible light irradiation, and Ag-AgI-AgIO3-5 sample shows the optimal photoreactivity, which is 15.2 times that of pure AgIO3. Notably, it also possesses unsurpassed photocatalytic activity against diverse industrial contaminants, pharmaceuticals, and gaseous NO. Besides, Ag-AgI-AgIO3-5 also displays better photocatalytic performance in converting CO2 to CO than AgIO3. Particularly, we explore the reduction products of AgIO3 by other different reductants. It is fascinating that the introduction of sodium citrate, thiourea and hydrazine hydrate results in the products Ag-AgIO3, AgI-AgIO3, Ag-AgI-AgIO3 composites, respectively. This work may not only offer a universally powerful and stable photocatalyst for environmental and energy applications, but also open up a new avenue to develop component-adjustable polynary heterostructural photocatalysts in a facile way.

Metal-free graphitic carbon nitride (g-C3N4) has sparked considerable interest due to its efficient photocatalytic activity in many fields. Development of new tactics toward improving the photocatalytic performance of g-C3N4 remains active and challenging. In this study, we uncover an unprecedented template-free precursor (melamine) pre-treatment protocol to achieve porous g-C3N4 nanosheets for efficient photocatalytic reduction and oxidation reaction. The introduction of thiourea solution in the hydrothermal pre-treatment process etches the surface of melamine, thus yielding the porous, thin g-C3N4 nanosheets. The microstructure and porosity of g-C3N4 can be adjusted only by controlling the thiourea amount. The as-obtained porous g-C3N4 nanosheets are found to be endowed with not only increased specific surface area, but also enhanced photoabsorption in the visible light region. Systematic characterizations of the charge movement behavior (transient photocurrent, linear sweep voltammetry, electrochemical impedance spectra, photoluminescence and surface photovoltage spectroscopy) disclose that the separation of photogenerated charge carriers is remarkably boosted by fabricating such a porous nanosheet structure. Benefiting from these advantages, porous g-C3N4 nanosheets present profoundly enhanced visible-light photocatalytic performance for H2 evolution (3.3-fold increase) and NO removal from the gaseous phase (5.5 times increase) in contrast to the pristine bulk g-C3N4. Our current study may offer an alternative approach to designing high-performance g-C3N4 nanomaterials for energy and environmental applications.

Synthesis of reactive exposing facets and p-n junction are of great importance for semiconductor photocatalysis. Herein, we develop a p-n junction BiOI@Bi12O17Cl2 heterostructure via facilely in situ depositing BiOI nanosheets on the surface of Bi12O17Cl2 plates. Owing to the charge inducement, the BiOI nanosheets are all vertically assembled onto the Bi12O17Cl2 large plates to form a unique front-lateral surfaces coupling heterostructure, which enables high exposure of {001} reactive exposing facets of BiOI. The photocatalytic properties are systematically evaluated by degrading multiform industrial contaminants and antibiotic, like 2,4-dichlorophenol (2,4-DCP), rhodamine B (RhB), phenol, bisphenol A (BPA), and tetracycline hydrochloride. It reveals that the BiOI@Bi12O17Cl2 heterostructure not only shows dramatically strengthened photocatalytic activity, but also unfold powerful and nonselective photooxidation ability under visible-light illumination. The photoelectrochemical characterizations demonstrated that the drastically promoted separation and transfer of charge carriers that derived from the benefits of BiOI {001} active facets and BiOI@Bi12O17Cl2 p-n junction are in charge of the high photo-activity. Detailed radicals detection and quantification experiments further corroborate our conclusions. The study may give us some new hints on designing novel heterostructured photoelectronic materials with integrating p-n junction and active exposing facets.

A facile and green process was developed for the synthesis of pyrochlore H4Nb2O7 hollow microspheres via the hydrothermal treatment of Sn2Nb2O7 hollow microspheres in aqueous 2M HCl at 100-180 oC. The facile transformation of Sn2Nb2O7 into H4Nb2O7 is facilitated by the intrinsic ion-exchange capability of Sn2Nb2O7. The resulting H4Nb2O7 hollow microspheres (diameter 1-2 μm, shell thickness 100-200 nm) displayed excellent photocatalytic performance for overall water splitting under UV irradiation, affording H2 and O2 evolution rates of 240 and 116 μmol h-1 g-1, respectively. Following decoration with 0.5 wt.% Pt, the H4Nb2O7 hollow microspheres demonstrated remarkably high H2 and O2 evolution rates of 1240 and 600 μmol h-1 g-1,respectively. To our knowledge, this work is the first reported study examining the photocatalytic performance of the H4Nb2O7 for water splitting. The hydrothermal synthesis method described here is also applicable to the synthesis of pyrochlore H4Ta2O7 from Sn2Ta2O7, highlighting the versatility of the approach.

Photoinduced syntheses offer significant advantages over conventional thermal strategies, including improved control over reaction kinetics and low synthesis temperatures, affording nanoparticles with nontrivial and thermodynamically unstable structures. However, the photoinduced syntheses of non-metallic nanocrystalline products (such as metal sulfides) have not yet been reported. Herein, we demonstrate the first photoinduced synthesis of ultrafine (sub-2 nm) Ag2S quantum dots (QDs) from Ag nanoparticles at 10 °C. By thorough investigation of the mechanism for the transformation, a fundamental link was established between the intrinsic structures of the molecular intermediates and the final Ag2S products. Our results confirm the viability of low-temperature photochemical approaches in metal sulfide synthesis, and demonstrate a new rule which could be followed in it.

We first achieve controllable synthesis of composition-adjustable polynary heterojunction photocatalysts via a facile in-situ treatment strategy at ambient conditions based on component transformation and chemical deposition. By controlling the chemical reaction degree, three-classes of heterojunction composites with diverse components were produced. The first group (G1) contains AgI/AgIO3 two phases. The second group (G2) consists of Bi7O9I3/AgI/AgIO3 three phases. While the last group (G3) is composed of Bi7O9I3/AgI. Along with different phase constitution, it is very intriguing to observe that photoabsorption edges of the composites can be orderly tuned from 400 nm to 650 nm, covering almost the whole visible light region, consistent with the color change of samples from white to light yellow, orange and brick red. The three series of composite photocatalysts all show greatly enhanced photocatalytic activity in photodegrading methyl orange (MO) and NO gas removal under simulated solar light or visible light irradiation compared with the AgIO3 precursor. Among them, the intense photoabsorption and desirable band alignment (three-rank heterojunction) are well balanced in Bi7O9I3/AgI/AgIO3, thus showing the optimal photoreactivity, approximately 128 times than that of AgIO3. Particularly, it also exhibits unsurpassed photocatalytic performance against diverse industrial pollutants and pharmaceutical, such as Rhodamine B, phenol, 2,4-dichlorophenol, bisphenol A, and tetracycline hydrochloride. Additionally, three types of photocatalytic mechanisms corresponding to the three series of photocatalysts are systematically investigated and illustrated. It is found that different phase composition has a huge impact on the separation and migration of charges as well as active species. The present work not only provides new perspective into manipulating component-adjustable heterojunctional photocatalysts, but also opens an alternative avenue for developing composite materials for solar-conversion applications.

Three series of ternary hierarchical architecture photocatalysts Ag/AgX (X = Cl, Br, I)/AgIO3 were fabricated for the first time by a facile in situ ion-exchange route. The novel ternary architectures are confirmed by XRD, XPS, SEM, TEM, EDX, and EDX mapping. In contrast to pristine AgIO3, the Ag/AgX (X = Cl, Br, I)/AgIO3 composites show extended absorption edges and highly boosted photoabsorption in the visible region, which are separately ascribed to the intrinsic absorption of AgX and the surface plasmon resonance (SPR) effect of Ag species. The photocatalysis activity of Ag/AgX (X = Cl, Br, I)/AgIO3 composites is studied and compared via photodegradation of methyl orange (MO) under visible-light (λ > 420 nm) irradiation. It is interesting to find that the activity enhancement levels are different for Ag/AgX (X = Cl, Br, I)/AgIO3 with four types of photocatalytic mechanism, which are closely related to the type of AgX or the component content in Ag/AgX (X = Cl, Br, I)/AgIO3. The separation behaviors of...

Semiconductor-based photocatalysis as a productive technology furnishes a prospective solution to environmental and renewable energy issues, but its efficiency greatly relies on the effective bulk and surface separation of photoexcited charge carriers. Exploitation of atomic-level strategies allows in-depth understanding on the related mechanisms and enables bottom-up precise design of photocatalysts, significantly enhancing photocatalytic activity. Herein, the advances on atomic-level charge separation strategies toward developing robust photocatalysts are highlighted, elucidating the fundamentals of charge separation and transfer processes and advanced probing techniques. The atomic-level bulk charge separation strategies, embodied by regulation of charge movement pathway and migration dynamic, boil down to shortening the charge diffusion distance to the atomic-scale, establishing atomic-level charge transfer channels, and enhancing the charge separation driving force. Meanwhile, regulating the in-plane surface structure and spatial surface structure are summarized as atomic-level surface charge separation strategies. Moreover, collaborative strategies for simultaneous manipulation of bulk and surface photocharges are also introduced. Finally, the existing challenges and future prospects for fabrication of state-of-the-art photocatalysts are discussed on the basis of a thorough comprehension of atomic-level charge separation strategies.

Intrinsic oxygen vacancies at CeO2 surface are known to activate thermodynamically stable CO2 molecules, enhancing the reaction rate and reducing reduction energy. However, charge recombination at the ceria-based cathode surface suppresses the multi-electron transfer process required for a complete reduction of CO2 molecules to generate useful hydrocarbons. To suppress this charge recombination and facilitate the multi-electron transfer process, p-type NiO and reduced graphene oxide (rGO) were hybridized with CeO2 to form rGO-grafted NiO-CeO2 photocatalyst, which can convert CO2 to formaldehyde at a rate of 421.09 μmol g−1 h−1; about 4 times higher than that of pristine CeO2. Formation of photo-induced oxygen vacancy of CeO2 photocatalyst resulted in a change of Ce-O bond length at ceria surface were monitored in-situ by X-ray absorption near edge structure (XANES), and X-ray absorption fine structure (EXAFS) spectroscopy. Tracking the formation of CO2 anion radical (CO2•-) and its subsequent protonation with in-situ electron paramagnetic resonance spectroscopy and attenuated total reflection-infrared (ATR-IR) spectroscopy, mechanism and reaction pathway of CO2 reduction into formaldehyde formation have been elucidated.

Electrochemical water splitting into hydrogen and oxygen in neutral electrolytes has great significance for future energy supply security, potentially offering a pathway for H2 generation from seawater. However, the electrocatalytic hydrogen evolution reaction (HER) generally occurs at low rates in neutral solutions due to the low proton concentration in such media. Herein, we fabricated a novel HER catalyst capable of efficient H2 evolution in water at neutral pH, comprising a nickel-molybdenum nitride nanowire array modified with metallic Ni nanoparticles (Ni/NiMoN). The entire Ni/NiMoN array was supported on a Cu foam. The Ni nanoparticles promoted the dissociation of adsorbed water to enhance the supply of protons in the neutral electrolyte, whilst the nanowire array imparted the electrode surface with underwater superaerophobic properties, thus allowing H2 gas bubbles to detach from the electrode in a facile manner. On the basis of the synergies realized between the different electrode components, the Ni/NiMoN nanowire array electrode offered exceptional HER performance, with an overpotential of only 37 mV at a current density of 10 mA cm−2 in a neutral electrolyte. Results guide the development of next-generation earth-abundant element electrocatalysts for HER in neutral media.

Nonmetallic cocatalysts have demonstrated unprecedented potential for accelerating photocatalytic hydrogen evolution reaction (HER). In this study, a nickel phosphide compound, namely Ni5P4, with porous carnation-like superstructure has been target-synthesized and then employed as HER cocatalyst to in-situ build a hybrid with protonated g-C3N4 nanosheets via an electrostatic self-assembly method. Owing to the synergistic advantages of the excellent metallic conductivity and porous carnation-like superstructure of Ni5P4, the as-obtained HCN/Ni5P4 Schottky-junction with abundant active sites, low H* atom adsorption energy and efficient charge carrier transport channel, affords the photocatalytic H2 production rate of 1157.5 μmol g−1 h−1 when exposed to visible light (λ > 420 nm). This photocatalytic H2 production rate was much higher than those of the corresponding reference cocatalysts, namely Ni2P and NiS2 (169.1 and 593.1 μmol g−1 h−1, respectively), both of which were derived from the same Ni(OH)2 precursor. This study provides a new idea for the design of highly active noble-metal-free materials for the photocatalytic HER.

Over the past decades, an enormous amount of research effort has been directed towards the discovery of high performance photocatalysts for solar hydrogen production via water splitting. Owing to their compositional flexibility, tunable optical and electronic properties, and ease of synthesis, niobium-based semiconductors offer great advantages in photocatalyst development for hydrogen generation. This review highlights recent advances in the development of niobium-based semiconductors for water splitting, placing special emphasis on structure-activity relationships. The fundamental principles of photocatalytic water splitting are first introduced, followed by a detailed description of the various niobium-based semiconductors synthesized to date and their classification based on structure and composition. Next, the activities of the different classes of niobium-based photocatalysts for solar-driven hydrogen production are critically explored, with a view towards future photocatalyst design and performance improvements. Finally, the authors offer a perspective on potential of niobium-based photocatalysts to contribute to future hydrogen economies.

The development of inexpensive, highly active, and stable non-precious metal catalysts is the key to efficient H2 production by the electrolysis of water. Based on initial theoretical predictions, we report the design and synthesis of N-doped, defect-containing, carbon-dots (CDs)-loaded molybdenum phosphide (MoP/CDs) nanoparticles using CDs with different N contents. This optimized composite material performed outstandingly in the hydrogen evolution reaction (HER), with an overpotential of 70 mV at a current density of 10 mA cm−2 with a 1.0 M KOH electrolyte. N doping changed the electronic arrangement around the reaction site, promoting the adsorption of HER intermediates. Increasing the N content further activated the adjacent C atoms to detach due to the more negative C vacancy formation energies resulting in a defect site with lost atoms and changed bond lengths. The introduction of defects increases the number of dangling bonds adjacent to reaction sites and reduces site coordination numbers, changing their electrocatalytic activity. Results show that N-doped and defect-containing MoP/CDs nanoparticles have excellent H2 production performance during the electrolysis of alkaline solution. These findings open a new area of application of heteroatom-doped CDs and provide new ideas for the design of efficient carbon-semiconductor composite HER catalysts.