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A direct Z-scheme heterojunction via decorating Ag3PO4 quantum dots on SnS2 nanosheets results in highly selective and efficient solar-driven CO2-to-CO photoreduction.

Owing to the passivation of surface states, low surface-potential fluctuations, and low charge-transfer resistance, an in situ electrochemically passivated photoanode shows higher photoelectrochemical performance and outstanding stability for ∼100 h.

Designing an organic polymer photocatalyst for efficient hydrogen evolution with visible and near-infrared (NIR) light activity is still a major challenge. Unlike the common behaviour of increasing the charge recombination gradually while shrinking the bandgap, here we present a series of polymers nanoparticles (Pdots) based on ITIC and BTIC units with different π-linkers between the acceptor-donor-acceptor (A-D-A) repeated moieties of the polymer, which acts as an efficient single polymer photocatalyst for H2 evolution under both visible and NIR light without combining or hybridizing with other materials. Importantly, the difluorothiophene (ThF) π-linker facilitates the charge transfer between acceptors of different repeated moieties (~ A-D-A-(π-Linker)-A-D-A~) leading to enhancement of charge separation between D and A. As a result, the PITIC-ThF Pdots exhibit superior hydrogen evolution rates of 339.7 mmol g− 1 h− 1 (0.279 mol/h) and 4100 µmol g− 1 h− 1 (20.5 µmol/h) with visible (> 420 nm) and NIR (> 780 nm) light irradiation, respectively. Furthermore, PITIC-ThF Pdots exhibit a record-breaking apparent quantum yield (AQY) at 700 nm (4.76%).

In this work, we, for the first time, observed the remarkable thermoelectric properties of a few high-quality PtSe2 layered films fabricated by a post selenization of Pt thin films. An excellent po...

Cu2ZnSnS4 (CZTS) has demonstrated excellent performance as an anode material for lithium-ion batteries. However, the repeated lithiation and delithiation create a cracking pattern and lead to island formation in the thin-film electrode, resulting in a capacity fading over cycling in lithium-ion batteries (LIB's). In order to control this crack behaviour, we introduce carbon into CZTS thin-films by a hydrothermal method to form CZTS@C composite. CZTS@C significantly reduced the crack pattern formation on the electrode surface as well as improved the conductivity of the CZTS@C electrode. At the early stages of lithiation and delithiation, the volume expansion and contraction of Li–CZTS@C create intra-granular cracking only at the surface level, and it offers a high capacity of about 785 mA h g−1 after 150 cycles at 1000 mA g−1 charging rate, excellent rate capability (942 mA h g−1, 678 mA h g−1 and 435 mA h g−1 at 500 mA g−1, 2000 mA g−1 and 5000 mA g−1), and superior cyclability (925 mA h g−1 even after 200 cycles at 500 mA g−1). The excellent electrochemical performance at high-current rates can be attributed to intra-granular cracking together with carbon coating that provides a short transportation length for both lithium ions and electrons. Moreover, the controlled cracking pattern formation in CZTS@C facilitates faster reaction kinetics, which open up a new solution for the development of high-power thin-film anodes for next-generation LIBs applications.

Most chemical vapor deposition methods for transition metal dichalcogenides use an extremely small amount of precursor to render large single-crystal flakes, which usually causes low coverage of the materials on the substrate. In this study, a self-capping vapor-liquid-solid reaction is proposed to fabricate large-grain, continuous MoS2 films. An intermediate liquid phase-Na2Mo2O7 is formed through a eutectic reaction of MoO3 and NaF, followed by being sulfurized into MoS2. The as-formed MoS2 seeds function as a capping layer that reduces the nucleation density and promotes lateral growth. By tuning the driving force of the reaction, large mono/bilayer (1.1 mm/200 μm) flakes or full-coverage films (with a record-high average grain size of 450 μm) can be grown on centimeter-scale substrates. The field-effect transistors fabricated from the full-coverage films show high mobility (33 and 49 cm2 V−1 s−1 for the mono and bilayer regions) and on/off ratio (1 ~ 5 × 108) across a 1.5 cm × 1.5 cm region., Here, the authors develop a self-capping vapour-liquid-solid reaction to fabricate large-grain continuous MoS2 films, whereby an intermediate liquid phase-Na2Mo2O7 is formed through a eutectic reaction of MoO3 and NaF, followed by sulphurisation into MoS2.

The mechanisms for O2 reduction and H2O/H2O2 formation on Co–corrin and Co–porphyrin cathode surfaces of the proton exchange membrane fuel cell (PEMFC) systems have been studied by hybrid Hartree–F...

In addition to the Ge-vacancy control of GeTe, the antimony (Sb) substitution of GeTe for the improvement of thermoelectric performance is explored for Ge1−xSbxTe with x = 0.08–0.12. The concomitant carrier concentration (n) and the aliovalent Sb ion substitution led to an optimal doping level of x = 0.10 to show ZT ∼ 2.35 near ∼800 K, which is significantly higher than those single- and multi-element substitution studies of the GeTe system reported in the literature. In addition, Ge0.9Sb0.1Te demonstrates an impressively high power factor of ∼36 μW cm−1 K−2 and a low thermal conductivity of ∼1.1 W m−1 K−1 at 800 K. The enhanced ZT level for Ge0.9Sb0.1Te is explained through a systematic investigation of micro-structural change and strain analysis from room temperature to 800 K. A significant reduction of lattice thermal conductivity (κlat) is identified and explained by the Sb substitution-introduced strained and widened domain boundaries for the herringbone domain structure of Ge0.9Sb0.1Te. The Sb substitution created multiple forms of strain near the defect centre, the herringbone domain structure, and widened tensile/compressive domain boundaries to support phonon scattering that covers a wide frequency range of the phonon spectrum to reduce lattice thermal conductivity effectively.

Recent advances in nanotechnology, especially the development of integrated nanostructured materials, have offered unprecedented opportunities for photocatalytic CO2 reduction. Compared to bulk semiconductor photocatalysts, most of these nanostructured photocatalysts offer at least one advantage in areas such as photogenerated carrier kinetics, light absorption, and active surface area, supporting improved photochemical reaction efficiencies. In this review, we briefly cover the cutting-edge research activities in the area of integrated nanostructured catalysts for photochemical CO2 reduction, including aqueous and gas-phase reactions. Primarily explored are the basic principles of tailor-made nanostructured composite photocatalysts and how nanostructuring influences photochemical performance. Specifically, we summarize the recent developments related to integrated nanostructured materials for photocatalytic CO2 reduction, mainly in the following five categories: carbon-based nano-architectures, metal-organic frameworks, covalent-organic frameworks, conjugated porous polymers, and layered double hydroxide-based inorganic hybrids. Besides the technical aspects of nanostructure-enhanced catalytic performance in photochemical CO2 reduction, some future research trends and promising strategies are addressed.

Effects of electronic and atomic structures of V-doped 2D layered SnS

The widespread use of energy storage technologies has created a high demand for the development of novel anode materials in Li-ion batteries (LIBs) with high areal capacity and faster electron-transfer kinetics. In this work, carbon-coated Cu

Ascertaining the function of in-plane intrinsic defects and edge atoms is necessary for developing efficient low-dimensional photocatalysts. We report the wireless photocatalytic CO

The quest of earth-abundant bifunctional electrocatalysts for highly efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential for clean and renewable energy systems. Herein, directed by the experimental analysis, we demonstrate layered nickel lithium phosphosulfide (NiLiP2S6) crystal as a highly efficient water-splitting catalyst in alkaline media. With strained lattice due to stacked layers as observed by TEM and electronic structure analysis performed by XPS showed mixed Ni2+,3+ oxidation states induced by addition of Li as a cation, NiLiP2S6 displays excellent OER (current density of 10 mA cm–2 showed an overpotential of 303 mV vs. RHE and a Tafel slope of 114 mV dec–1) and HER activity (current density of −10 mA cm–2 showed an overpotential of 184 mV vs. RHE and a Tafel slope of 94.5 mV dec–1). Finally, an alkaline media was employed to demonstrate the overall water splitting using NiLiP2S6 as both the anode and the cathode, which attained a 50 mA cm−2 current density at 1.68 V. This bimetallic phosphosulfide, together with long-term stability and enhanced intrinsic activity, shows enormous potential in water splitting applications.

Germanium tellurides and its pseudo binary compounds offer interesting properties that are important in thermoelectric and phase-change applications. Despite being a class of materials under scrutiny since its discovery, unique properties and functionalities kept on emerging in recent years. In this work, we observed another unique property of Ge-Sb-Te (GST) thin film that can be beneficial in its development for thermoelectric application. A rapid heating and quenching process of the GST film resulted in a metastable rock-salt cubic structure, exhibiting a unique electronic-transition-like behavior. Above the transition temperature at 150 °C, we observed a temperature-induced band modulation, corroborated with changes in its effective mass and valence band position that leads to favorable electronic and thermoelectric properties. Charge transfer between Sb and Te occurred, accompanied by a distorted cubic-to-cubic structural change. The interplay of the electronic and lattice structure born out of the co...

Interface engineering of CdS/CZTS(Se) is an important aspect of improving the performance of buffer/absorber heterojunction combination. It has been demonstrated that the crossover phenomenon due to the interface recombination can be drastically eliminated by interface modification. Therefore, in-depth studies across the CdS/CZTS(Se) junction properties, as well as effective optimization processes, are very crucial for achieving high-efficiency CZTSSe solar cells. Here, we present a comprehensive study on the effects of soft-baking (SB) temperature on the junction properties and the corresponding optoelectronic and interface-structural properties. Based on in-depth photoemission studies corroborated with structural and composition analysis, we concluded that interdiffusion and intermixing of CZTSSe and CdS phases occurred on the Cu-poor surface of CZTSSe at elevated SB temperatures, and the interface dipole moments induced by electrostatic potential fluctuation were thus significantly eliminated. In contrast, with low SB temperature, the CdS/CZTSSe heterojunction revealed very sharp interface with very short interdiffusion, forming interface dipole moments and drastically deteriorating device performance. These post thermal treatments also significantly suppress defect energy level of interface measured by admittance spectroscopy from 294 to 109 meV due to CdS/CZTSSe interdiffusion. Meanwhile, the interdiffusion effects on the shift of valence band maximum, conduction band minimum and band offset across the heterojunction of thermally treated CdS/CZTSSe interface are spatially resolved at the atomic scale by measuring the local density of states with cross-sectional scanning tunneling microscopy and spectroscopy. A significant enhancement in the power conversion efficiency from 4.88% to 8.48% is achieved by a facile interface engineering process allowing a sufficient intermixing of CdS/Cd and CZTSSe/Se phases without detrimental recombination centers.

Tuning the electronic band structure of black titania to improve photocatalytic performance through conventional band engineering methods has been challenging because of the defect-induced charge carrier and trapping sites. In this study, KSCN-modified hydrogenated nickel nanocluster-modified black TiO2 (SCN–H–Ni–TiO2) exhibits enhanced photocatalytic CO2 reduction due to the interfacial dipole effect. Upon combining the experimental and theoretical simulation approach, the presence of an electrostatic interfacial dipole associated with chemisorption of SCN has dramatic effects on the photocatalyst band structure in SCN–H–Ni–TiO2. An interfacial dipole possesses a more negative zeta potential shift of the isoelectric point from 5.20 to 3.20, which will accelerate the charge carrier separation and electron transfer process. Thiocyanate ion passivation on black TiO2 demonstrated an increased work function around 0.60 eV, which was induced by the interracial dipole effect. Overall, the SCN–H–Ni–TiO2 photocat...

Designing highly conducting metal–organic frameworks (MOFs) is currently a subject of great interest for their potential applications in diverse areas encompassing energy storage and generation. Herein, a strategic design in which a metal–sulfur plane is integrated within a MOF to achieve high electrical conductivity, is successfully demonstrated. The MOF {[Cu2(6-Hmna)(6-mn)]·NH4}n (1, 6-Hmna = 6-mercaptonicotinic acid, 6-mn = 6-mercaptonicotinate), consisting of a two dimensional (–Cu–S–)n plane, is synthesized from the reaction of Cu(NO3)2, and 6,6′-dithiodinicotinic acid via the in situ cleavage of an S–S bond under hydrothermal conditions. A single crystal of the MOF is found to have a low activation energy (6 meV), small bandgap (1.34 eV) and a highest electrical conductivity (10.96 S cm−1) among MOFs for single crystal measurements. This approach provides an ideal roadmap for producing highly conductive MOFs with great potential for applications in batteries, thermoelectric, supercapacitors and related areas.

A highly reproducible sample preparation method for pure GeTe in a rhombohedral structure without converting to the cubic structure up to ∼500 °C is reported to show control of the Ge-vacancy level and the corresponding herringbone-structured microdomains. The thermoelectric figure-of-merit (ZT) for GeTe powder could be raised from ∼0.8 to 1.37 at high temperature (HT) near ∼500 °C by tuning the Ge-vacancy level through the applied reversible in situ route, which made it highly controllable and reproducible. The enhanced ZT of GeTe was found to be strongly correlated with both its significantly increased Seebeck coefficient (∼161 μV K−1 at 500 °C) and reduced thermal conductivity (∼2.62 W m−1 K−1 at 500 °C) for a sample with nearly vacancy-free thicker herringbone-structured microdomains in the suppressed rhombohedral-to-cubic structure phase transformation. The microdomain and crystal structures were identified with HR-TEM (high-resolution transmission electron microscopy) and powder X-ray diffraction (XRD), while electron probe micro-analysis (EPMA) was used to confirm the stoichiometry changes of Ge : Te. Theoretical calculations for GeTe with various Ge-vacancy levels suggested that the Fermi level shifts toward the valence band as a function of increasing the Ge-vacancy level, which is consistent with the increased hole-type carrier concentration (n) and effective mass (m*) deduced from the Hall measurements. The uniquely prepared sample of a near-vacancy-free GeTe in a rhombohedral structure at high temperature favoured an enhanced Seebeck coefficient in view of the converging L- and Σ-bands of the heavy effective mass at the Fermi level, while the high density domain boundaries for the domain of low carrier density were shown to reduce the total thermal conductivity effectively.

Exploring electrocatalysts composed of earth-abundant elements for a highly efficient hydrogen evolution reaction (HER) is scientifically and technologically important for electrocatalytic water splitting. In this work, we report HER properties of acid treated pyrolyzed vitamin B12 supported on reduced graphene oxide (B12/G800A) that shows an extraordinarily enhanced catalytic activity with low overpotential (115 mV vs. RHE at 10 mA cm−2), which is better than that of most traditional nonprecious metal catalysts in acidic media. Stability tests through long-term potential cycles and at a constant current density confirm the exceptional durability of the catalyst. Notably, the B12/G800A catalyst exhibits extremely high turnover frequencies per cobalt site in acid, for example, 0.85 and 11.46 s−1 at overpotentials of 100 and 200 mV, respectively, which are higher than those reported for other scalable non-precious metal HER catalysts. Moreover, it has been conjectured that the covalency of Co–C and Co–N bonds affects HER activities by comparing the extended X-ray absorption fine structure (EXAFS) spectra of the B12/G800A. High-temperature treatment can modify the Co-corrin structure of B12 to form Co–C bonds along with Co–N, which broadens the band of cobalt, essentially lowering the d-band center from its Fermi level. The lower d-band center leads to a moderate hydrogen binding energy, which is favorable for hydrogen adsorption and desorption.

Photocatalytic water splitting is a promising way to produce hydrogen fuel from solar energy. In this regard, the search for new photocatalytic materials that can efficiently split water into hydrogen is essential. Here, using first-principles simulations, we demonstrate that the dual-defective SnS2 (Ni-SnS2-VS), by both single-atom nickel doping and sulfur monovacancies, becomes a promising two-dimensional photocatalyst compared with SnS2. The Ni-SnS2-VS monolayer, in particular, exhibits a suitable band alignment that perfectly overcomes the redox potentials for overall water splitting. The dual-defective monolayer displays remarkable photocatalytic activity, a spatially separated carrier, a broadened optical absorption spectrum, and enhanced adsorption energy of H2O. Therefore, the dual-defective SnS2 monolayer can serve as an efficient photocatalyst for overall water splitting to produce hydrogen fuel. Furthermore, a novel dual-defect method can be an effective strategy to enhance the photocatalytic behavior of 2D materials; it may pave inroads in the development of solar-fuel generation.

Earth-abundant Cu2ZnSn(S,Se)4 (CZTSSe) is a promising nontoxic alternative compound for commercially available Cu(In,Ga)(S,Se)2 thin-film solar cells. In this study, a MoO3 nanolayer was applied as a sacrificial layer to optimize the quality of the interface between the CZTSSe and Mo back contact. MoO3 nanolayers can greatly improve CZTSSe grain growth and suppress the formation of some harmful secondary phases, especially the undesirable MoS(e)2. In terms of device performance, the series resistance was reduced from 1.83 to 1.54 Ω·cm2, and the fill factor was significantly enhanced from 42.67% to 52.12%. Additionally, MoO3 nanolayers improved CZTSSe absorber quality by lowering the defect energy levels from 228 to 148 meV. Furthermore, first-principles calculations demonstrate that the partial sulfoselenized MoO3 nanolayers may function as the (p-type) hole-selective contacts at Mo/CZTSSe interfaces, leading to an overall improvement in device performance. Lastly, a CZTSSe solar cell with about 26% improvement (compared with reference cells) in power conversion efficiency was achieved by inserting 5 nm MoO3 sacrificial layers.

This work demonstrates the first example of interfacial manipulation in a hybrid photocatalyst based on poly(3-hexylthiophene-2,5-diyl) (P3HT) nanoparticle and graphene oxide (GO) bulk heterojunctions to efficiently reduce CO2 into selective industrial hydrocarbons under gas-phase reaction and visible-light illumination. High selectivity of chemical products (methanol and acetaldehyde) was observed. Moreover, the hybrid photocatalyst’s solar-to-fuel conversion efficiency was 13.5 times higher than that of pure GO. The increased production yield stems from the co-catalytic and sensitizing role of P3HT in the hybrid system due to its ability to extend light absorption to the visible range and improve interfacial charge transfer to GO. The hybrid P3HT-GO formed a type II heterojunction, and its static and dynamic exciton behaviors were examined using fluorescence spectroscopy and exciton lifetime mapping. A reduced fluorescence decay time was observed by interfacial manipulation for improved dispersion, indicating a more efficient charge transfer from the excited P3HT to GO. Thus, the conducting polymer nanoparticles, 2D nanocarbon, have demonstrated superior performance as a metal-free, non-toxic, low-cost, and scalable heterogeneous photocatalyst for CO2 reduction to solar fuel, a solid–gas system.

Pharmaceutical drugs' removal from wastewater by photocatalytic oxidation process is considered as an attractive approach and environmentally friendly solution. This report aims to appraise the practical application potential of Ag/g-C