Search

A series of supported MgO/γ-Al 2 O 3 composites (denoted as Mg/Al-x) with enhanced adsorption performance towards CO 2 were successfully synthesized via a facile one-pot cation-anion double hydrolysis approach. Their phase structures, morphologies, textural properties and basic properties were comparatively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), N 2 adsorption-desorption, in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) and CO 2 temperature programmed desorption (CO 2 -TPD). Three kinds of carbonates including bicarbonate, bidentate and monodentate carbonate are formed during the adsorption process, indicating a synergistic adsorption mechanism for CO 2 . For the dynamic CO 2 adsorption without water vapor, the adsorption capacity decreases in the order of Mg/Al-0.2 > Mg/Al-0.3 > Mg/Al-0.1 > Mg/Al-0, which coincides with the trend of the amount of basic sites; especially, Mg/Al-0.2 with the Mg/Al molar ratio of 0.2 shows a stable adsorption capacity of 1.60 mmol/g without loss after 11 cycles at 60 °C. Furthermore, water vapor shows a positive effect on their adsorption, and Mg/Al-0.2 reaches an adsorption capacity of 2.10 mmol/g for the simulated flue gas with 10 vol% water vapor at 60 °C. Its relatively high adsorption capacity, excellent cyclic adsorption/desorption stability and facile preparation process make it an attractive candidate for CO 2 capture with flue gas conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical Pt/Co 3 O 4 -NiO catalyst prepared from MOFs with excellent activity. • Hollow and porous structure with low air resistance and fast diffusion channels. • Abundant active oxygen species at the interface between Co 3 O 4 and NiO. • Enhanced O 2 adsorption and activation due to the electron transfer from NiO to Pt. • Possible mechanism for HCHO oxidation over Pt/Co 3 O 4 -NiO proposed. Room-temperature catalytic decomposition is considered a predominant approach for the continuous and efficient elimination of indoor formaldehyde (HCHO). Herein, Co 3 O 4 -NiO hollow dodecahedra were prepared by using ZIF-67 as a precursor and decorated with 0.3 wt% platinum nanoparticles (Pt NPs). The hierarchical porous Pt/Co 3 O 4 -NiO catalyst exhibited an excellent room-temperature HCHO decomposition performance, and 93% conversion was achieved within 60 min. Numerous active oxygens at the interface between Co 3 O 4 and NiO and the oxygen vacancies generated during Pt deposition were favorable for the adsorption and conversion of HCHO to Dioxymethylene (DOM). Moreover, the electron transfer from NiO to Pt rendered Pt NPs more effective in adsorbing and activating O 2 molecules, thereby promoting the further oxidation of DOM to formate and CO 2. Importantly, the hierarchical structure of the Co 3 O 4 -NiO support with a large surface area participated in the uniform distribution and easy accessibility of Pt active sites. In addition, the hollow and porous structure enabled Pt/Co 3 O 4 -NiO catalyst to possess ultra-low gas resistance, which is important for gas–solid HCHO oxidation. This work may provide clues for the fabrication of MOF-derived catalysts for HCHO decomposition with high efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis of bifunctional mesostructured alumina via amino-functionalization. [•] P123 extraction and tetraethylenepentamine loading were simultaneously realized. [•] The amino-functionalized alumina shows excellent mesostructure centering at 7.3nm. [•] Good adsorptive capability of the amino-functionalized alumina for Cr(VI) and CO2. [•] The amino-functionalized alumina shows very fast adsorption kinetics for Cr(VI). [ABSTRACT FROM AUTHOR]

[Display omitted] • This novel inorganic/organic CdS/COF 2D-2D S-scheme heterostructure is designed. • The structure can reduce charge transfer distance, and improve light absorption. • This S-scheme heterojunction enhances charge separation and retains redox ability. • The CdS/COF exhibits a remarkable photocatalytic H 2 production rate. • The heterojunction converts ascorbic acid to value-added 2,3-diketo-L-gulonic acid. It is an efficient strategy to construct photocatalysts by integrating the advantages of inorganic semiconductors and covalent organic frameworks (COFs) for H 2 generation along with simultaneous organic oxidation. Herein, an inorganic/organic CdS/COF (denoted as TpBD) 2D heterostructure is fabricated by an electrostatic self-assembly method. The ultrathin 2D structure can reduce charge transfer distance, enhance light absorption, and multiply reaction sites while the S-scheme heterojunction improves the charge separation efficiency. The CdS/COF composite acquires an outstanding photocatalytic activity of 15.1 mmol/g/h, and can simultaneously convert cheap ascorbic acid to value-added 2,3-diketo-L-gulonic acid. The Hall effect test elucidates the dynamics of carrier migration. The electron paramagnetic resonance analysis, photo-irradiated Kelvin probe force microscopy, femtosecond transient absorption spectroscopy, theoretical calculation, and in-situ irradiation X-ray photoelectron spectroscopy measurements confirm the superiority of S-scheme heterojunction for charge carrier transfer. This research presents new inspiration to develop efficient photocatalysts for hydrogen production and green chemical production. [ABSTRACT FROM AUTHOR]

• Plasmonic Cu/Cu 2 O octahedrons fabricated via an electroless reduction method. • The CO 2 photoreduction (PR) activity is investigated. • Plasmon-induced interfacial charge-transfer transition (PICTT) is realized. • Much higher CO 2 PR activity fostered by the PICTT mechanism. • The unique PICTT induced PR under approximate NIR irradiation. The plasmon-induced interfacial charge-transfer transition (PICTT) involves the direct electron transfer from a plasmonic metal to the acceptor state in a semiconductor (SC). Such plasmonic decay is fostered by strong orbital coupling and mixing of electronic levels in plasmonic metals and SC. Although the effectiveness of PICTT for charge transfer has been testified, its realization still remains a great challenge. Herein, we employed a facile electroless reduction strategy for the in-situ growth of copper (Cu) nanoparticles (NPs) over Cu 2 O ordered octahedrons. Amorphous carbon formed at the Cu 2 O surface via calcination provides an electroless reduction configuration for the conversion of Cu ions within Cu 2 O lattice into Cu NPs. The in-situ growth guarantees a rational couple of Cu 2 O with its derivative Cu NPs. Such a unique arrangement enables extension of optical absorption range as well as achievement of PICTT upon excitation of Cu-localized surface plasmon resonance (LSPR), which promotes desirable CO 2 photoreduction activity under near-infrared irradiation. This work provides an effective strategy for constructing plasmonic-metal/metal-oxide composites with enhanced photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hierarchical honeycomb-like NiFe-layered double hydroxide (LDH)/rGO was obtained. • The NiFe-LDH/rGO was deposited with Pt to yield the Pt/NiFe-LDH/rGO composite. • HCHO oxidation activity of the Pt/NiFe-LDH/rGO composite was firstly investigated. • The Pt/NiFe-LDH/rGO composite displays excellent HCHO degradation performance. • The intermediates in HCHO decomposition process were detected by in situ DRIFTS. Abstract Formaldehyde (HCHO) is regarded as the most ubiquitous indoor pollutant, which causes severe health symptoms for humans. Catalytic oxidation at ambient temperature has been identified as the most promising technique for indoor HCHO removal. Herein, a hierarchical honeycomb-like nanocomposite of reduced graphene oxide (rGO) and nickel-iron layered double hydroxide (NiFe-LDH) was prepared via a hydrothermal method. After decoration of the NiFe-LDH/rGO with 0.34 wt% of platinum (Pt), the Pt/NiFe-LDH/rGO showed excellent catalytic performance for HCHO degradation at room temperature, which are due basically to the better dispersion of both NiFe-LDH and rGO in the composite. This structural characteristic endows Pt/NiFe-LDH/rGO with larger surface area, thus resulting in plentiful surface active sites and highly dispersed Pt nanoparticles, which are conducive to the activation of both surface oxygen atoms of NiFe-LDH and adsorbed oxygen molecules. Moreover, dioxymethylene and formate were major reaction intermediates, while surface hydroxyl groups and surface active oxygen atoms were the key species involved in the catalytic reaction, which shed light on the HCHO oxidation mechanism. This work demonstrates that introducing graphene materials into hierarchical catalysts can enhance the removal of gaseous HCHO and potentially other indoor pollutants. [ABSTRACT FROM AUTHOR]

• Zinc porphyrin/g-C 3 N 4 S-scheme photocatalyst is developed via –CONH-bridging bond. • Zn-TCPP/CN exhibits H 2 O 2 production rate with 3.1 times higher than pure CN. • Two-step single-electron route is the predominant reaction step in H 2 O 2 generation. • S-scheme charge transfer path greatly facilitates the spatial charge separation. • DFT reveals strong interface interaction with the electron delocalization effect. Constructing heterojunction photocatalyst is a promising strategy to achieve solar-to-chemical energy conversion. Especially, the S-scheme heterojunction has received a great deal of attention because of its superiority of the efficient photogenerated charge carriers' separation and the strong photoredox capacity. Herein, an S-scheme heterojunction is designed and synthesized through grafting supramolecular Zinc porphyrin (Zn-TCPP) on g-C 3 N 4 (CN) via –CONH- bridging bond for H 2 O 2 production in the O 2 atmosphere under a 300 W Xe lamp irradiation using ethanol as a sacrificial agent. As the optimal sample, Zn-TCPP/CN exhibits the highest H 2 O 2 production rate with 532.7 μmol/L within 90 min, which is 3.1 and 9.0 times higher than those of pure CN and Zn-TCPP, respectively. The route of H 2 O 2 production in the photocatalytic process and the mechanism of activity enhancement are revealed by a systematic characterisation. Hence, the results of the radical trapping experiment and rotating disk electrode measurement demonstrate that the two-step single-electron route is the predominant reaction step in the process of H 2 O 2 generation. In-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and Kelvin probe force microscopy (KPFM) technology provide strong evidence of the S-scheme charge transfer path between Zn-TCPP and CN, which greatly facilitates the spatial charge separation. Meanwhile, the density functional theory (DFT) calculations reveal that the strong interface interaction between Zn-TCPP and CN can induce the electron delocalization effect, thus restraining charge recombination. This work inspired the design of a high-active metalloporphyrin-based S-scheme heterojunction for energy conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni@O-Ni pre-electrocatalyst with porous and O-riched surface was in-situ prepared. • Ni@O-Ni undergoes self-reconstruction processes to generate actual active sites. • Ni@Ni/NiO x and Ni@Ni/NiO x were fabricated via cathodic/anodic activation processes. • Ni@Ni/NiO x shows a low overpotential of 71 mV to reach 10 mA cm−2 for HER. • Ni@NiO x exhibits a yield (∼99 %) of Ph-COOH product for Ph-CH 2 OH electro-oxidation. In-situ surface self-reconstruction of electrocatalysts plays a crucial role in efficiently catalyzing the hydrogen evolution reaction (HER) and the organic compound oxidation reaction. Herein, a core@shell structure of metallic Ni@O-riched Ni layer (Ni@O-Ni) pre-electrocatalyst was established, which possesses a unique self-adaptable ability for the potential-dependent reconstruction to generate actual active sites for catalytic reactions. The reconstructed Ni@Ni/NiO x during the cathodic activation process shows an outstanding HER activity with a low overpotential of 71 mV to reach 10 mA cm−2 and remarkable stability in 1.0 M KOH. In addition, the core@shell structured Ni@NiO x during the anodic activation process contributes to abundant redox reactions for the electro-oxidation of organic compound. Especially, the Ni@NiO x exhibits an ultralow potential of 1.309 V at 10 mA cm−2 and ∼ 99 % yield of benzoic acid (Ph-COOH) product for the electro-oxidation of benzyl alcohol (Ph-CH 2 OH). In-situ Raman spectra corroborate the reversible transformation of Ni2+ - O x and γ-Ni3+ – OOH and reveal the vital role of γ-Ni3+ – OOH in seizing the proton for Ph-CH 2 OH electro-oxidation reaction. Moreover, the constructed integrated water splitting coupled with Ph-CH 2 OH electro-oxidation needs only a cell voltage of 1.438 V at 10 mA cm−2, resulting in an electrical energy saving of 14.3 % compared to overall water splitting. This work proposes profound insights into the correlation between surface features, potential-dependent reconstruction, and the multifunctionality of electrocatalysts. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride/titania (g-C 3 N 4 /TiO 2 ) composite photocatalysts with different C 3 N 4 /TiO 2 ratios were synthesised by a simple preparation route through annealing the mixtures of melamine and commercial TiO 2 P25 powder at 550 °C for 3 h under Ar flow. The resulting composite photocatalysts were characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and electrochemical impedance spectroscopy. The photocatalytic activity of the composites was evaluated using NO as a target inorganic air pollutant. Variation of the initial weight ratio of melamine precursor/TiO 2 (3:1, 1:1, 2:3, 1:3, 1:4 and 1:7) allowed tuning of the composites’ band gap from 2.66 eV in pure g-C 3 N 4 to 3.14 eV in pure P25 as revealed by UV–visible spectroscopy. The conduction band edges position determined by electrochemical measurements using Mott–Schottky relation varied from ∼−1.27 eV in pure g-C 3 N 4 to ∼−0.67 eV in pure P25 (vs NHE, pH 7). Under visible light, the g-C 3 N 4 /TiO 2 composite with initial ratio 1:4 exhibited superior photocatalytic activity in NO oxidation in comparison to the pure semiconductors g-C 3 N 4 and TiO 2 . This finding was explained to be a result of a combination of the optical and electronic properties of the composites. [ABSTRACT FROM AUTHOR]

[Display omitted] • An electron-rich regulation idea was developed to weaken the strong S-H ads bonds. • The active-sulfur number and efficiency of MoWS 2+ x was simultaneously optimized. • The S-rich MoWS 2+ x was prepared by one-step photoinduced electron-reduction method. • H 2 -evolution rate of TiO 2 can be significantly improved by S-rich MoWS 2+ x. Metal chalcogenides (MS x) as H 2 -evolution cocatalysts generally suffer from unfavorable H desorption property because of the strong interfacial interaction between the adsorbed H and intensely electronegative S sites (S-H ads , 363 KJ mol−1), which seriously hampers the H ads from desorbing to generate free H 2. Herein, a universal strategy of electron-enriched regulation of sulfur-active site is developed to weaken the strong S-H ads bonds by introducing W heteroatoms into MoS 2+ x to form sulfur-rich MoWS 2+ x bimetal cocatalyst (expressed as MoWS 2+ x). In this case, the S-enriched MoWS 2+ x is skillfully produced and simultaneously anchored with the TiO 2 by a facile photoinduced electron-reduction method, involving the aforehand formation of homogeneous W(MoS 4) x and their subsequent in-situ photoinduced deposition procedure. Photoactivity experiments exhibit that the MoWS 2+ x /TiO 2 (2:1) sample obtains the highest H 2 -evolution rate of 4620.8 μmol h−1 g−1 (AQE = 22.2 %) with a great promotion of 3.6 folds compared to the MoS 2+ x /TiO 2 sample. In situ/ex situ XPS characterizations and density functional theory (DFT) calculations reveal that the integration of W heteroatom into MoS 2+ x can regulate its electron density to form electron-enriched S(2+δ)− sites, thus availably weakening the S-H ads bonds to optimize atomic H desorption and accordingly enhancing the hydrogen-evolution activity of TiO 2. This study provides a unique idea to optimize the electron densities of activity sites, which is vital for the development of efficient catalytic materials. [ABSTRACT FROM AUTHOR]

• A novel COF-based ZnO/TpPa-Cl composite prepared by electrostatic self-assembly. • S-scheme heterojunction is constructed between TpPa-Cl and ZnO. • ZnO/TpPa-Cl composite exhibited improved photocatalytic H 2 O 2 production. • Effective separation of photogenerated charges and enhanced redox capacity are concurrently achieved. Covalent organic frameworks (COFs) are burgeoning crystalline porous materials with great potential in photocatalysis, but their applications are mainly restricted by the speedy recombination rate of charge carriers. Herein, a step-scheme heterojunction ZnO/COF(TpPa-Cl) is fabricated by a simple electrostatic self-assembly method, and its photocatalytic H 2 O 2 production performance is also investigated. The S-scheme heterojunction between ZnO and TpPa-Cl contributes to enhanced light absorption, promoted reactant adsorption capacity, increased redox power, and efficient separation and transfer of photogenerated charge carriers, leading to an improved photocatalytic H 2 O 2 evolution activity. The optimal composite possesses the maximum H 2 O 2 evolution rate of 2443 μmol·g−1·h−1 under simulated solar light irradiation, which is about 3.3 and 8.7 times higher than pristine ZnO nanoparticles and TpPa-Cl, respectively. Moreover, the charge transfer pathway in S-scheme heterojunction photocatalysts is well elucidated. This investigation provides designing guidelines in the construction of other COF-based S-scheme heterojunctions. [ABSTRACT FROM AUTHOR]

[Display omitted] • CC@NiO/Ni 3 S 2 was efficiently developed by a facile one-step electrodeposition. • NiO/Ni 3 S 2 interfaces induce the charge redistribution to enhance catalytic activity. • CC@NiO/Ni 3 S 2 shows a bifunctional catalytic activity for HER and Ph-CH 2 OH oxidation. • A two-electrode electrolyzer with an electrical energy saving of 10.0 % is constructed. Coupling electrocatalytic water splitting (EWS) with benzyl alcohol (Ph-CH 2 OH) oxidation can efficiently suppress the sluggish water oxidation and boost hydrogen production efficiency. However, it remains an enormous challenge to design the corresponding bifunctional electrocatalysts with high activity, high selectivity, and long-term stability. Herein, 2D Ni-based nanoarrays grown directly on carbon cloth (CC) substrate (CC@NiO/Ni 3 S 2) were synthesized using a facile one-step electrodeposition technique. The CC@NiO/Ni 3 S 2 consists of ultrathin nanosheets (∼3.4 nm) with rich NiO/Ni 3 S 2 heterointerfaces, which not only efficiently exposes more active sites and accelerates mass/charge diffusion, but also provides unique interfacial interactions for charge redistribution to activate the formation of key reaction intermediates. As a result, the CC@NiO/Ni 3 S 2 exhibits a low overpotential of 91 mV at 10 mA cm−2 with high catalytic stability for catalyzing hydrogen evolution reaction (HER). When the Ph-CH 2 OH oxidation is chosen as the corresponding anodic half-reaction instead of water oxidation, the CC@NiO/Ni 3 S 2 also shows an excellent catalytic activity as well as a high selectivity (over 98%) towards benzoic acid (Ph-COOH), which is a value-added chemical and can be easily separated by crystallization. A two-electrode electrolyzer was accordingly constructed using CC@NiO/Ni 3 S 2 as the cathode and anode electrocatalysts for HER and Ph-CH 2 OH oxidation, respectively, showing stable production of hydrogen fuels and value-added Ph-COOH. More importantly, the H 2 generation rate is boosted by 2.6 times at 1.609 V by replacing water oxidation with Ph-CH 2 OH oxidation, which can also save electrical energy of 10.0 % at 50 mA cm−2. This work offers a facile strategy to develop advanced bifunctional electrocatalysts with abundant heterointerfaces for practical applications in energy-saving hydrogen production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel Ni-based metal–organic framework (MOF)/CdS with outstanding performance for photocatalytic hydrogen generation. • Numerous atomically dispersed Ni-N 4 reduction sites confined in MOF boosting the photocatalytic activity. • The process of electron-hole separation and migration greatly facilitated by MOF. The depletion of traditional fossil fuels and related environmental issues have increased the demand for clean and sustainable energy resources to achieve carbon neutrality. Active, robust and cheap photocatalysts are required for large-scale photocatalytic H 2 evolution reaction (p-HER), which transforms solar energy into chemical energy. Here we report the decoration of Ni-imidazole framework (NiIm) with CdS nanorods for p–HER. The p–HER rate of CdS/NiIm hybrid sharply increased by about 14.23 times to 21,712 µmol h−1 g–1 when compared with that of CdS alone. Physicochemical characterizations and theoretical calculations reveal strong interactions at the CdS/NiIm interface and the presence of numerous Ni–N 4 active sites on NiIm leading to the significant performance enhancement. This work demonstrates that NiIm acts as an affordable and abundant co-catalyst that remarkably enhances the p–HER, and enlightens the further development in the design and preparation of metal−organic framework-based materials for various applications in photocatalysis and related subjects. [ABSTRACT FROM AUTHOR]

Highlights: [•] The porous γ-Al2O3 was prepared by surfactants-assisted hydrothermal method. [•] Morphology changes of γ-Al2O3 are highly dependent on the surfactants. [•] The products exhibit high adsorption capacities for parachlorophenol in water. [Copyright &y& Elsevier]

Abstract: The porous α-Fe2O3 nanomaterials were prepared using glycine as structure-directing agent via a simple hydrothermal synthesis followed by calcination. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), nitrogen adsorption–desorption isotherms measurement. The as-obtainted α-Fe2O3 presents crosslinked hierarchical pore structure on small meso (ca. 15nm), large meso (ca. 40nm) and macro (ca. 100–200nm) length scales. The equilibrium adsorption data of p-nitrophenol on the as-prepared samples were well fitted by the Langmuir isothermal model. The adsorption kinetics was found to follow the pseudo-second-order equation. The Fe2O3 samples are found to be effective adsorbent for the removal of p-nitrophenol from wastewater as a result of their high surface area and accessible diffusion pathways of porous network. [Copyright &y& Elsevier]

[Display omitted] • The design strategy of highly-active photocatalysts was summarized. • Improving crystallinity, reducing particle size and increasing the surface area. • Constructing heterojunction and loading cocatalysts. • S-scheme heterojunction with suitable band-gap and dual cocatalysts. Due to the severe energy and environmental crisis, solar fuels are receiving wide attention. They are generated by solar-driven photocatalytic systems. Highly-active photocatalytic materials are cardinal for this promising technology. However, they suffer from rapid carrier recombination, limited solar light adsorption, as well as deficient active sites. To overcome these drawbacks and develop efficient photocatalysts, various strategies have been devised. In this perspective, we attempt to summarize the recent development of highly-active photocatalysts designed from three aspects: light-harvesting, charge separation and transport, and surface redox reactions. This perspective mainly focuses on i) developing visible-light response photocatalysts, ii) constructing heterojunction photocatalysts, and iii) loading cocatalysts. It is expected that further innovative works on the design of highly-active photocatalytic materials for solar fuel production can be inspired by this perspective. [ABSTRACT FROM AUTHOR]

[Display omitted] • The design strategy of highly-active photocatalysts was summarized. • Improving crystallinity, reducing particle size and increasing the surface area. • Constructing heterojunction and loading cocatalysts. • S-scheme heterojunction with suitable band-gap and dual cocatalysts. Due to the severe energy and environmental crisis, solar fuels are receiving wide attention. They are generated by solar-driven photocatalytic systems. Highly-active photocatalytic materials are cardinal for this promising technology. However, they suffer from rapid carrier recombination, limited solar light adsorption, as well as deficient active sites. To overcome these drawbacks and develop efficient photocatalysts, various strategies have been devised. In this perspective, we attempt to summarize the recent development of highly-active photocatalysts designed from three aspects: light-harvesting, charge separation and transport, and surface redox reactions. This perspective mainly focuses on i) developing visible-light response photocatalysts, ii) constructing heterojunction photocatalysts, and iii) loading cocatalysts. It is expected that further innovative works on the design of highly-active photocatalytic materials for solar fuel production can be inspired by this perspective. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel amorphous NiCuS x H 2 -evolution cocatalyst was anchored onto TiO 2. • Amorphous NiCuS x nanoparticles possess electron-rich active S sites for H 2 evolution. • H 2 -evolution rate of TiO 2 can be greatly enhanced by amorphous NiCuS x nanoparticles. • An optimized surface-hydrogen-desorption mechanism of a-NiCuS x cocatalyst was raised. Cost-effective nickel sulfide has attracted great interest as a favorable cocatalyst for achieving highly-efficient photocatalytic activity, but its H 2 -evolution performance is still suppressed owing to the strong sulfur-hydrogen bonds (S-H ads). In this study, the interfacial S-H ads bonds can be effectively weakened by the formation of the electron-rich active S sites via introducing Cu atoms into the amorphous NiS x cocatalyst. By use of a precursor-complexation photodeposition strategy, novel amorphous NiCuS x H 2 -evolution cocatalyst (a-NiCuS x) have been constructed and simultaneously anchored onto TiO 2 to form a-NiCuS x /TiO 2 photocatalysts. Photocatalytic results reveal that the optimized a-NiCuS x /TiO 2 (3:1) photocatalyst (427.9 μmol h−1, AQE = 34.67%) achieves an enhanced H 2 -generation activity compared to the a-NiS x /TiO 2 (226.1 μmol h−1). As investigated by density-functional-theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS), the Cu heteroatom into a-NiS x can induce its charge redistribution to form electron-rich active S sites, thereby effectively weakening the S-H ads bonds to optimize hydrogen adsorption and accordingly boosting the photocatalytic H 2 -generation rate. This work offers a promising and rational method to optimize the catalytic centers of a H 2 -evolution cocatalyst, presenting great potential in designing highly-efficient photocatalyst for future scalable and sustainable H 2 production. [ABSTRACT FROM AUTHOR]

• In-situ growth of graphene on ZnO surface by CVD method. • Intimate interfacial contact is beneficial to the charge transfer. • Graphene can effectively trap the photogenerated electrons from ZnO. • Photothermal effect of graphene contributed to the performance enhancement. Intimate interfacial contact between semiconductor photocatalysts and cocatalysts is important for the transfer and separation of photogenerated charge carriers. Herein, few-layer graphene, as an efficient cocatalyst, was in-situ deposited on the surface of ZnO. The composite demonstrated improved photocatalytic CO 2 reduction performance than pristine ZnO, ascribing to the intimate interfacial contact and Schottky junction between ZnO and graphene. Meanwhile, photothermal effect of graphene and π-π conjugation interaction between graphene and CO 2 molecules also contributed to the performance enhancement. This work not only provides a feasible approach for the in-situ growth of graphene, but also develops an efficient photocatalyst for CO 2 reduction. [ABSTRACT FROM AUTHOR]

• ZnMn 2 O 4 /ZnO nanocomposites are prepared. • High yields of CO and CH 4 are concurrently achieved. • DFT calculation explores their band structures. • Charge separation is greatly improved via S-scheme mechanism. • The outcome extends S-scheme heterojunctions to p-type and n-type semiconductors. Inspired by the carbon cycle in nature, it is promising to convert CO 2 into energy-dense hydrocarbon fuels via photocatalytic CO 2 reduction. In the present paper, hierarchical ZnMn 2 O 4 /ZnO nanofibers were prepared as photocatalysts by electrospinning and calcination. They outperformed pristine ZnO nanofibers with about 4-fold increment in CO and CH 4 yields. Except for the advantages coming from the design, such as more exposed active sites and multiple light reflections, other benefits derived from interface charge transfer are also important. To uncover this, density functional theory calculation (DFT), along with X-ray photoelectron spectroscopy (XPS) was performed. Photoluminescence (PL) and time-resolved PL spectroscopy revealed that the charge separation efficiency in the composite was significantly elevated. Step-scheme (S-scheme) charge transfer was testified in the composite. This result, for the first time, exemplifies that S-scheme charge-transfer can also be realized in heterojunction based-on p-type ZnMn 2 O 4 and n-type ZnO. It provides a new insight into the design of other S-scheme photocatalysts, which are composed of p-type and n-type semiconductors. [ABSTRACT FROM AUTHOR]

• Selenium-enriched amorphous NiSe 1+ x as a new cocatalyst was deposited onto TiO 2. • Selenium-enriched amorphous NiSe 1+ x has more unsaturated active Se atoms. • H 2 -evolution rate of TiO 2 was improved by selenium-enriched amorphous NiSe 1+ x. • An enriched Se-mediated mechanism of NiSe 1+ x was proposed. Exploiting and fabricating of novel non-noble metal cocatalysts with abundant active sites is highly required to boost the photocatalytic performance. Herein, selenium-enriched amorphous NiSe 1+ x nanoclusters (a-NiSe 1+ x) as a novel cocatalyst were rationally integrated with the TiO 2 to greatly boost its hydrogen-generation rate via a simple photoinduced deposition route. It was interesting to find that in comparison with the crystalline nickel selenide (c-NiSe), the a-NiSe 1+ x evidently displayed more unsaturated active Se atoms because of its highly irregular arrangement structure and small particle size (0.5–2 nm). Photocatalytic results revealed that the a-NiSe 1+ x nanoclusters could significantly improve the hydrogen-production activity of TiO 2 (4095.3 μmol h−1 g−1, AQE = 19.6%), which is higher than that of pristine TiO 2 and c-NiSe/TiO 2. The outstanding performance of a-NiSe 1+ x /TiO 2 can be attributed to the synergism of facilitated photoelectron transfer from TiO 2 to a-NiSe 1+ x cocatalyst and excellent H 2 -production active site of Se atoms, which was well revealed by density functional theory (DFT) calculations and in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) measurement. Based on the above results, an enriched Se-mediated mechanism is raised for the boosted H 2 -generation rate of a-NiSe 1+ x /TiO 2. Moreover, the present a-NiSe 1+ x can also be used as the general cocatalyst for typical g-C 3 N 4 and CdS photocatalysts. Considering the gentle preparation, low-cost and admirable activity, the a-NiSe 1+ x cocatalyst would have tremendous prospects for the fabrication of advanced photocatalytic materials. [ABSTRACT FROM AUTHOR]

• Ternary BiVO 4 -N/C-CoPOM photoanode is constructed. • High photocurrent density of 3.30 mA cm−2 and low onset potential are achieved. • Much higher applied bias photon-to-current efficiency and fill factor are achieved after depositing CoPOM. • Charge injection efficiency is greatly improved after depositing CoPOM. Photoelectrochemical (PEC) water splitting can convert solar power into clean energy carrier of hydrogen, which is a promising strategy to address the global energy crisis and environmental issues. At present, the sluggish kinetics of the separation and migration of the photo-excited electrons and holes for water oxidation is the bottleneck for the high solar-to-hydrogen efficiency in this field. Herein, we exploit cobalt polyoxometalate (CoPOM) as a novel molecular cocatalyst locating at N-doped carbon (N/C) to boost the charge separation and injection of BiVO 4 photoanodes for PEC water oxidation. Comprehensive results reveal that the uniformly distributed CoPOM specially improves the hole injection efficiency, leading to the lower onset potential of water oxidation and confirming the improved the kinetics of BiVO 4 photoanode for PEC water splitting. A high maximum applied bias photon-to-current efficiency of 1.22% is achieved at a low potential of 0.63 V vs. reversible hydrogen electrode (RHE) for BiVO 4 -N/C-CoPOM, and the photocurrent density of increases up to 1.93 mA cm−2 at 0.63 V vs. RHE and 3.30 mA cm−2 at 1.23 V vs. RHE, which are 11.4 and 5.4 times higher than that of the pristine BiVO 4, respectively. Particularly, the significantly improved PEC performance in the low bias range indicates CoPOM can effectively reduce the water oxidation energy barrier. We believe this research provides a novel molecular cocatalyst of POM for the improvement of PEC performance of photoanode, and expands the scope for the design of efficient cocatalysts for solar energy-conversion devices. [ABSTRACT FROM AUTHOR]

• An ethyl acetate-induced route was developed to prepare a-MoS x /TiO 2 photocatalysts. • The amorphous MoS x nanoclusters are in the range of 0.4–0.7 nm. • The a-MoS x /TiO 2 photocatalysts clearly achieve an improved H 2 -evolution activity. • More unsaturated S atoms work as effective active sites to boost H 2 -evolution rate. Amorphous MoS x has been demonstrated to be a high H 2 -production cocatalyst towards various photocatalytic materials, and the facile synthetic route of MoS x cocatalyst with a small size is highly required to further improve its H 2 -evolution performance. In this study, amorphous MoS x nanoclusters (a-MoS x) with a very small size of 0.4–0.7 nm have been successfully loaded on TiO 2 surface by an ethyl acetate-induced hydrolysis route. Herein, the MoS 4 2− ions can be gradually and homogeneously transformed into amorphous MoS x nanoclusters on the TiO 2 surface to prepare the highly efficient a-MoS x /TiO 2 photocatalysts via the gradual hydrolysis of ethyl acetate. The photocatalytic hydrogen-production experimental results reveal that the resulting a-MoS x /TiO 2 (5 wt%) photocatalyst achieves the maximum H 2 -evolution rate (1106 μmol h−1 g−1), which is apparently higher than that of crystalline MoS x -modified TiO 2 (94 μmol h−1 g−1) by a factor of 11.71 times. The markedly enhanced H 2 -evolution rate of the a-MoS x /TiO 2 photocatalyst can be attributed to the formation of more unsaturated S atoms in the amorphous MoS x nanoclusters, which can work as effective active sites to boost the interfacial H 2 -production rate. The present facile method may provide rational ideas for preparing other nanocluster materials for energy and environmental applications. [ABSTRACT FROM AUTHOR]