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To utilize the UV and visible lights and to improve the separation of photoinduced carriers, a composite composed of NaLiTi3O7 and graphite-carbon nitride (g-C3N4) was constructed. The morphology and microscopic structural details of NaLiTi3O7/g-C3N4 photocatalyst were characterized using XRD, SEM, TEM, XPS, FT-IR, UV-DRS, and TGA techniques. XRD and SEM results showed that well-crystalline NaLiTi3O7 nanoparticles were well dispersed on the surface of g-C3N4 sheets and that the introduction of g-C3N4 effectively alleviated the aggregation of NaLiTi3O7 nanoparticles. UV-DRS results further suggested that the light absorption edge of the NaLiTi3O7/g-C3N4 composite had a significant redshift. Due to these advantages, NaLiTi3O7/g-C3N4 composites exhibited good photocatalytic performance. The hydrogen production performance of all NaLiTi3O7/g-C3N4 samples was much better than that of pure g-C3N4 and NaLiTi3O7 under solar irradiation, and the best NaLiTi3O7/g-C3N4 composite produced 18 times more hydrogen than pure NaLiTi3O7 and 4 times more hydrogen than pure g-C3N4. Compared with pure NaLiTi3O7 or g-C3N4 phases, coupling NaLiTi3O7 with g-C3N4 significantly improved the photocatalytic performance due to the formation of the heterojunction interface between them, which was favorable for the effective separation of the photogenerated electron and hole in a wide light absorption range. [ABSTRACT FROM AUTHOR]

To improve the photocatalytic performance of semiconductor catalysts, one of the most widely used strategies is to combine two or more semiconductors with appropriate energy band structures to construct heterojunctions for an extended light absorption range and effective charge separation. Here, a novel Z-scheme heterojunction is fabricated via the Cd0.3Zn0.7S twin crystal and the narrow band gap semiconductor Ag3PO4. The resulting Cd0.3Zn0.7S/1%Ag3PO4 photocatalyst exhibits excellent photocatalytic hydrogen production capability (167.29 μmol h−1), which is two times higher than that of Cd0.3Zn0.7S and 44/7 times higher than that of pristine ZnS/CdS. The excellent photocatalytic performance is not only attributed to the defective twin crystal structure of Cd0.3Zn0.7S but also related to the well-matched Z-scheme interface between Cd0.3Zn0.7S and Ag3PO4, and both factors effectively promote the separation of the photogenerated electron–hole pairs and prolong the lifetime of the carriers, being responsible for the excellent photocatalytic hydrogen evolution performance of the catalysts. This strategy provides new insights into the construction of efficient twin crystal heterojunctions for photocatalytic hydrogen evolution with high performance. [ABSTRACT FROM AUTHOR]

Perovskite oxides with tailored elements and structures endow promising electrocatalytic properties for hydrogen evolution reaction (HER) due to considerable activity and satisfactory long‐term operating stability. However, the synthesis of 1D perovskite nanostructures with anion dopants remains a challenge, as well as insights into the performance origin from experimental and theoretical views. Herein, combined with electrospinning and phosphatizing strategies, P‐doped Pr0.5La0.5BaCo2O5+δ perovskite nanofibers (P‐PLBC‐F) are reported for highly active HER catalysts. The P‐PLBC‐F catalyst outperforms the classic perovskites and can be comparable to the commercial Pt/C (wtPt= 20%) benchmark, exhibiting a Tafel slope of −32.9 mV dec−1 and overpotential of −307 mV at 500 mA cm−2disk in alkaline media. The highly catalytic activity benefits from the desired 1D nanostructure, steered electronic structures (charge transfer energy ΔCo‐P= 0.79 eV) and Gibbs free energy for the H* desorption (1.02 eV) induced by the P3− doping, as supported by density functional theory calculations. The findings described here unveil the phosphatizing mechanism of the perovskites for catalyzing the hydrogen production, and broaden horizons in terms of rational designs of novel perovskite‐based catalysts for sustainable energy. [ABSTRACT FROM AUTHOR]

It is vital to exploit non-noble metal catalysts with ample natural reserve and high performance for reducing energy consumption during electrocatalytic water splitting process. Herein, nanocoral-like bimetallic Co-Mo carbide/nitrogen-doped carbon (Co-Mo2C/N-C) electrocatalysts have been successfully prepared by high temperature pyrolysis of CoMoO4 and melamine for hydrogen evolution reaction (HER). When the mass ratio of CoMoO4 and melamine is 1:15, nanocoral-like Co-Mo2C/N-C electrocatalyst shows optimal electrocatalytic HER activity, which just needs overpotentials of only 212 and 290 mV at the current density of 10 and 40 mA cm−2, respectively. Besides, it shows low charge transfer resistance and surpassing stability for uninterrupted HER in 1.0 M KOH electrolyte. The eximious electrochemical performance of Co-Mo2C/N-C is put down to the fact that N-C can effectively disperse Co-Mo2C nanoparticles. The results suggest that nanocoral-like Co-Mo2C/N-C with considerable catalytic activity and superior durability is believed as promising candidate to substitute noble metal catalysts for green and renewable hydrogen production by electrocatalytic water splitting. [ABSTRACT FROM AUTHOR]

A highly active and cheap catalyst is also key to hydrogen production by water splitting. However, most of the high‐efficiency catalysts reported to date only are catalytically active for either the hydrogen evolution reaction (HER) or the oxygen evolution reaction (OER), which makes the development of multifunctional catalysts more meaningful. Here, for the first time, Co(CO3)0.5OH.0.11 H2O (CHCH) as precursor with different microstructures on the surface of nickel foam (NF) was obtained using a facile hydrothermal method. The CoP/NF catalyst was obtained after thermal phosphating that retained the microhierarchical structure of the precursor and greatly improved the catalytic performance, with a highly efficiency performance as HER and OER dual‐functional catalyst. Density functional theory (DFT) calculations showed that the possible reason for the excellent performance of the CoP/NF layered structure is an increase in the number of of surface defects and an increased active surface area. The results reported in this paper show that CoP/NF, a layered bifunctional electrocatalyst, is a cost‐effective and efficient water‐splitting electrode. This finding can offer the opportunity for the commercial use of excess electric energy for large‐scale water splitting hydrogen production. [ABSTRACT FROM AUTHOR]

Gasification of glycerol for hydrogen production in supercritical water was studied in a fluidisation bed system with the presence of Na2CO3 and ZnCl2. The influence of main parameters, including temperature, pressure, feedstock concentration and catalyst addition, on the gasification process was discussed. The experiment results show that temperature is the key factor and pressure has a minor effect on glycerol gasification. Higher temperature and pressure are in favour of glycerol gasification. Gasification performance of glycerol decreases with the increasing concentration, and 35 wt.% glycerol was gasified stably during long time operations. Gasification efficiency increases and molar fraction of CO decreases with Na2CO3 addition. ZnC12 addition has no significant effect on the gasification efficiency, but it improves the selectivity of hydrogen in gas product. It is implied that the supercritical water fluidisation bed system is effective for hydrogen production by biomass gasification. [ABSTRACT FROM AUTHOR]

Gasification of glycerol for hydrogen production in supercritical water was studied in a fluidisation bed system with the presence of Na2CO3 and ZnCl2. The influence of main parameters, including temperature, pressure, feedstock concentration and catalyst addition, on the gasification process was discussed. The experiment results show that temperature is the key factor and pressure has a minor effect on glycerol gasification. Higher temperature and pressure are in favour of glycerol gasification. Gasification performance of glycerol decreases with the increasing concentration, and 35 wt.% glycerol was gasified stably during long time operations. Gasification efficiency increases and molar fraction of CO decreases with Na2CO3 addition. ZnC12 addition has no significant effect on the gasification efficiency, but it improves the selectivity of hydrogen in gas product. It is implied that the supercritical water fluidisation bed system is effective for hydrogen production by biomass gasification. [ABSTRACT FROM AUTHOR]

Gasification of glycerol for hydrogen production in supercritical water was studied in a fluidisation bed system with the presence of Na2CO3 and ZnCl2. The influence of main parameters, including temperature, pressure, feedstock concentration and catalyst addition, on the gasification process was discussed. The experiment results show that temperature is the key factor and pressure has a minor effect on glycerol gasification. Higher temperature and pressure are in favour of glycerol gasification. Gasification performance of glycerol decreases with the increasing concentration, and 35 wt.% glycerol was gasified stably during long time operations. Gasification efficiency increases and molar fraction of CO decreases with Na2CO3 addition. ZnCl2 addition has no significant effect on the gasification efficiency, but it improves the selectivity of hydrogen in gas product. It is implied that the supercritical water fluidisation bed system is effective for hydrogen production by biomass gasification. [ABSTRACT FROM AUTHOR]

Gasification of glycerol for hydrogen production in supercritical water was studied in a fluidisation bed system with the presence of Na2CO3 and ZnCl2. The influence of main parameters, including temperature, pressure, feedstock concentration and catalyst addition, on the gasification process was discussed. The experiment results show that temperature is the key factor and pressure has a minor effect on glycerol gasification. Higher temperature and pressure are in favour of glycerol gasification. Gasification performance of glycerol decreases with the increasing concentration, and 35 wt.% glycerol was gasified stably during long time operations. Gasification efficiency increases and molar fraction of CO decreases with Na2CO3 addition. ZnCl2 addition has no significant effect on the gasification efficiency, but it improves the selectivity of hydrogen in gas product. It is implied that the supercritical water fluidisation bed system is effective for hydrogen production by biomass gasification. [ABSTRACT FROM AUTHOR]

A phase-mixed MgTiO3–MgTi2O5 heterogeneous nanorod is fabricated via an ethylene glycol-mediated route to promote the photocatalytic hydrogen production activity significantly. The excellent charge separation and fast electron transport are the main reasons for the high efficiency due to the formation of phase-mixed heterogeneous junctions. [ABSTRACT FROM AUTHOR]

Investigating the synthesis and properties of diiron azadithiolate complexes is one of the key topics for mimicking the active site of [FeFe]‐hydrogenases, which might be very useful for the design of new efficient catalysts for hydrogen production and the development of a future hydrogen economy. A series of new phosphine‐substituted diiron azadithiolate complexes as models for the active site of [FeFe]‐hydrogenases are described. A novel and efficient way was firstly established for the preparation of phosphine‐substituted diiron azadithiolate complexes. The reaction of Fe2(μ‐SH)2(CO)6 and phosphine ligands L affords the intermediate Fe2(μ‐SH)2(CO)5L (A). The intermediate reacts in situ with a premixed solution of paraformaldehyde and ammonium carbonate to produce the target phosphine‐substituted diiron azadithiolate complexes Fe2[(μ‐SCH2)2NH](CO)5L (1a–1f) (L = P(C6H4–4‐CH3)3, P(C6H4–3‐CH3)3, P(C6H4–4‐F)3, P(C6H4–3‐F)3, P(2‐C4H3O)3, PPh2(OCH2CH3)). Furthermore, reactions of the intermediate A with I‐4‐C6H4N(CH2Cl)2 in the presence of Et3N give the phosphine‐substituted diiron azadithiolate complexes Fe2[(μ‐SCH2)2NC6H4–4‐I](CO)5L (2a–2e) (L = P(C6H4–4‐CH3)3, P(C6H4–3‐CH3)3, P(C6H4–4‐F)3, P(C6H4–3‐F)3, P(2‐C4H3O)3). All the complexes were fully characterized using elemental analysis, IR and NMR spectroscopies and, particularly for 1a, 1c–1e, 2a and 2c, single‐crystal X‐ray diffraction analysis. In addition, complexes 1a–1f and 2a–2e were found to be catalysts for H2 production under electrochemical conditions. Density functional theory calculations were performed for the reactions of Fe2(μ‐SH)2(CO)6 + P(C6H4–4‐CH3)3. [ABSTRACT FROM AUTHOR]

Designing titanium-based oxides with efficient photogenerated carrier separation is an essential approach to enhance their photocatalytic hydrogen production performance. ALiTi 3 O 7 possesses excellent stability, corrosion resistance, and non-toxicity. More importantly, its stoichiometry can be changed along with the variations in A-site elements and Li content, leading to tunable redox potentials of the conduction band minimum (CBM) and valence band maximum (VBM). Exploring the possible application of such materials in the field of photocatalysis is crucial for developing novel and efficient titanium-based photocatalysts. As a member of the family, NaLiTi 3 O 7 (NLT) has a large bandgap, limiting its application as visible light photocatalyst. To address this issue, non-toxic La 2 S 3 (LS) narrow-bandgap semiconductor was incorporated to form a heterojunction. The characterization techniques have revealed the structural and interfacial characteristics of the NLT-LS heterojunction, while the Infrared, Raman, UV–Vis diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), and work-function tests elucidated the influence of the interface interaction on charge carrier separation mechanism. The test results further demonstrated that the formation of a type II heterojunction facilitated the transfer of photogenerated electrons from the conduction band of LS to the conduction band of NLT under light radiation. Simultaneously, the induced holes were confined to the valence band of LS. This charge transfer characteristic significantly improved the separation efficiency of the photogenerated carriers in the heterojunction, ultimately resulting in a photocatalytic hydrogen production rate of 102.4 μmol h−1 g−1 for the NLT-LS2 sample, which is ∼8 times higher than that of pure NLT and almost no decay after four cycles. • A novel and very stable photocatalyst based on NaLiTi 3 O 7 and La 2 S 3 were successfully constructed. • The type-II heterojunctions have extended light adsorption capability and promising charge separation efficiency. • The photocatalytic production rate of H 2 reaches 102.4 μmol h−1 g−1. • Demonstration of NaLiTi 3 O 7 as a promising photocatalyst is important for the design of novel Ti-based oxides. [ABSTRACT FROM AUTHOR]

Hetero-element doping or vacancy defects of g-C 3 N 4 framework were found significantly to control its electronic structure and enhance photocatalytic activity under visible light. Herein, we fabricated P-doped tubular g-C 3 N 4 (P-TCN) with surface carbon defects wherein the P-doping and carbon defects were conveniently introduced during thermal polymerization of a supramolecular precursor. The supramolecular precursor of rod-like morphology was obtained only from melamine molecules under a sodium pyrophosphate-assisted hydrothermal process. As contrast, similar P-doped g-C 3 N 4 tubes were obtained using other phosphates, such as ammonium phosphate, sodium hypophosphite and sodium phosphite, thus highlighting the versatility of this method to tune the morphology and C/N ratio for g-C 3 N 4 tubes. The photocatalytic activities of P-TCNs were evaluated using hydrogen evolution from water under visible light. Among these, P-TCN obtained by sodium pyrophosphate-assisted hydrothermal reaction showed the highest photocatalytic activity due to high P element doping, enhanced visible light absorption and improved charge separation. The novel synthetic method described here thus represents an effective way of non-metal doping and C/N ratio tuning of g-C 3 N 4 with excellent photocatalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The underlying mechanism of MXenes-based materials is uncovered for water splitting. • The optimization strategy for high-efficiency MXenes-based materials is proposed. • An insight into the future direction of MXenes-based electrocatalysts is prospected. Water splitting has been considered as a sustainable and environmentally-friendly technique to realize green hydrogen production. However, the production of H 2 fuel is restricted by the sluggish kinetics and high overpotentials of the hydrogen evolution and oxygen evolution reactions. It is crucial to seek for high-efficiency electrocatalysts to boost the performance of water splitting. Among a great class of nanomaterials, MXenes-based nanomaterials can be utilized as excellent substrates to design novel materials due to their large specific surface area (SSA), fast electronic transmission, and excellent mechanical stability. However, the breakthroughs are at the experimental synthesis stage and lack all understanding of basic principles on catalytic mechanism, and then severely impede the development of high-efficiency electrocatalyst. Hence, some challenges still need to be clarified and resolved for further applications in electrocatalytic water splitting. In this review, the recent process on the synthesis routes, physical properties and performance improvement strategies for electrocatalytic water splitting of MXenes are summarized. We comprehensively summarize the electrocatalytic water splitting mechanism of MXenes both experimentally and theoretically. The in-depth discussion on structure–activity relationships and the basic understanding on electrocatalytic mechanisms of MXenes are also reviewed. At last, an insight into the future challenges, opportunities and further research directions of MXenes and related materials in the water-splitting application is prospected. This review offers a significant understanding for the design and optimization of high-efficiency MXenes-based electrocatalysts in water-splitting applications. [ABSTRACT FROM AUTHOR]