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The formation of heterojunctions has been identified as the most promising strategy for circumventing the constraints of the g-C 3 N 4 photocatalyst, including sluggish surface kinetics and rapid recombination loss of photoexcited electron and hole pairs. Combining g-C 3 N 4 with other semiconductors to form S-scheme heterojunctions can boost charge carrier surface migration, reduce recombination loss, and maintain high redox potentials, which synergistically improve the photocatalytic performance of g–C 3 N 4 –based systems. However, as the development and understanding of g–C 3 N 4 –based S-scheme catalysts has advanced, several conflicts and confusions have emerged, which must be clarified to widen the scope applicability of g–C 3 N 4 –based photocatalysts. To understand whether the charge migration route in g–C 3 N 4 –based heterojunctions is type-II or S-scheme, this review includes a systematic discussion with the support of theoretical models and advanced experimental techniques that illustrate the requirements for building type-II and S-scheme charge migration. Furthermore, in contrast to the conventional role, the actual function of Fermi levels bending at equalization in g–C 3 N 4 –based S-scheme heterojunctions to provide the potential difference for maintaining the interfacial built-in electric field, the persistence of driving, and strategies to strengthen the driving force are explained in depth. The current review offers fresh insights into the criteria used to establish the prerequisites for the creation of g–C 3 N 4 –based type-II and S-scheme heterojunctions. • Confusion between g–C 3 N 4 –based S-scheme and type-II charge migration route is clarified. • The actual role of Fermi levels instead of ideal in g-C 3 N 4 S-scheme heterojunction is discussed. • The persistence of driving force in g–C 3 N 4 –based S-scheme heterojunctions and associated strategies are introduced. • Characterization techniques to identify the S-scheme charge migration route are described. [ABSTRACT FROM AUTHOR]

The current study employs both theoretical and experimental methods to investigate the effect of Ti and Co doping on the WO 3 nanocomposite with MoS 2 photoanode's photoelectrochemical (PEC) water-splitting reaction. A simple hydrothermal and sol-gel method was adopted for the preparation of samples. The Ti-doped WO 3 –MoS 2 (1.96 at %) sample showed the maximum optical absorption with a photocurrent density of 1.15 mA/cm2 at 1.6 V vs Ag/AgCl. The improvement in photocurrent density may be ascribed to the upward shifting of the conduction band edge towards the H+/H 2 redox potential as well as the presence of a large number of active sites in MoS 2. A high value of flat band potential of −0.3 V vs Ag/AgCl was achieved in Ti-doped WO 3 –MoS 2 , which was confirmed by Mott-Schottky measurements with the corresponding lowest charge transfer resistance at the semiconducting electrode/electrolyte interface. Furthermore, density functional theory calculations have also indicated that on doping WO 3 with Ti and Co, there is a slight upward shift in the conduction band minimum, without any significant change in the valence band maximum, with respect to the Fermi level. This study provides new insight into the impact of transition metal doping and nanocomposite of chalcogenide materials for WO 3 -based PEC electrodes. [Display omitted] • Ti and Co-doped WO 3 nanorods and MoS 2 nanoflowers were prepared using a cost-effective sol-gel and hydrothermal method. • MoS 2 plays a crucial role in boosting the PEC response due to the presence of a large number of active sites. • Improved charge carrier separation and enhanced PEC response were achieved in 1.96 at% Ti-doped WO 3 –MoS 2 sample. • DFT calculations showed that on doping WO 3 with Ti and Co, a slight upward shift in CBM, without any notable change in VBM, with respect to Fermi level. [ABSTRACT FROM AUTHOR]

Coking is bottleneck problem during steam cracking processes, so strategies for online catalytic conversion of coke are vitally important for ethylene production. In this work, a method for regulating the band bap of perovskites to enhance hydroxyl radical generation is proposed to promote the catalytic conversion of coke. A series of ternary La 1- x Sr x FeO 3 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) perovskites were successfully prepared by sol-gel method. Experimental and DFT calculations show that Sr doped at A sites facilitates a reduction in the band gap and the promotion of electronic transitions in the perovskites. Moreover, water molecule adsorption, decomposition, and intermediate transition state desorption are improved. Using 10 wt % LSF-0.6 catalyst, a water flow rate of 0.167 mL/min, reaction temperature of 900 °C, and reaction time of 120 min, a coke conversion rate of 85.56% is achieved. This work provides a theoretical basis for in-situ high-efficiency coke removal. Perovskite LaFeO 3 is doped with s-block metal strontium (Sr) to regulated band gap of perovskite and move the O 2 p -band center up relative Fermi level, which enhances the generation of free ·OH radicals and the efficient in-situ conversion of coke. [Display omitted] [ABSTRACT FROM AUTHOR]

The composite MoO 3 / Me MoO 4 (Me = Cu, Ni, Co, Fe, and Mn) ceramics were obtained by standard high-temperature sintering. Their structure was tested using XRD, SEM, EDS, and XPS. The occurrence of two phases was determined. The main MoO 3 phase exhibited an orthorhombic Pnma space group related to the ceramic grain of micrometre size. The second phase was induced by doping with the Me atom. It showed various monoclinic structures and a smaller grain size. The XPS test confirmed the coexistence of the phases, which was reflected in several lines in the patterns. The valence band of the undoped MoO 3 was located ∼3.3 eV below the Fermi level. An additional subband attributed to the Me 3d state was detected within the energy gap. The MoO 3 / Me MoO 4 composites showed a valence band shifted toward the Fermi level and overlapped with the subband, originating from hybridized Mo 4d – Me 3d states. Magnetic susceptibility showed an antiferromagnetic state below ∼20 K for the Ni- and Fe-doped composites. The estimated magnetic moment magnitudes indicated the contribution from Me 2+ and Me 3+ ions that marked the occurrence of oxygen vacancies. Diffuse reflectance spectra exhibited anomalies in the Vis (∼500–650 nm) and the NIR (∼700–850 nm) ranges and tails in the ∼900–1000 nm range. The estimated magnitudes of energy gaps were attributed to defect-induced states. They corresponded to deduced oxygen vacancies (2.05–2.38 eV) and states or subbands induced by the introduced Me atoms (1.34–1.89 eV). Electric dc resistivity temperature dependence showed thermally activated dependence. The estimated activation energy varied from 0.27 eV to 0.58 eV, depending on the doping of the Me atom. The electric features were consistent with the electronic structure determined using XRD and XPS tests. [ABSTRACT FROM AUTHOR]

[Display omitted] α -Sn is an elemental topological material, whose topological phases can be tuned by strain and magnetic field. Such tunability offers a substantial potential for topological electronics. However, InSb substrates, commonly used to stabilize α -Sn allotrope, suffer from parallel conduction, restricting transport investigations and potential applications. Here, the successful MBE growth of high-quality α -Sn layers on insulating, hybrid (001) CdTe/GaAs substrates, with bulk electron mobility approaching 20000 cm2V−1s−1 is reported. The electronic properties of the samples are systematically investigated by independent complementary techniques, enabling thorough characterization of the 3D Dirac (DSM) and Weyl (WSM) semimetal phases induced by the strains and magnetic field, respectively. Magneto-optical experiments, corroborated with band structure modelling, provide an exhaustive description of the bulk states in the DSM phase. The modelled electronic structure is directly observed in angle-resolved photoemission spectroscopy, which reveals linearly dispersing bands near the Fermi level. The first detailed study of negative longitudinal magnetoresistance relates this effect to the chiral anomaly and, consequently, to the presence of WSM. Observation of the π Berry phase in Shubnikov-de Haas oscillations agrees with the topologically non-trivial nature of the investigated samples. Our findings establish α -Sn as an attractive topological material for exploring relativistic physics and future applications. [ABSTRACT FROM AUTHOR]

Although great progress has been made in the study of the performance of NiFe-based electrocatalysts, the specific role of Fe is still under debate, largely due to the lack of desirable platforms. Metal-organic frameworks (MOFs) with uniform pore size, large specific surface area and uniform distribution of active sites are ideal platforms. Therefore, we synthesized a series of NiM-MOF (M = Fe, Co, Mn, Cu, or Zn) nanosheet arrays by solvothermal method with MOF as a platform and systematically investigated their OER properties. XRD and XPS characterizations show that the introduction of Fe into Ni-MOF not only leads to lower crystallinity, but also increases the oxidation state of Fe and modifies the electronic structure of Ni sites. This is further confirmed by DFT calculations, where the d-band center is closer to the Fermi level, enhancing the ability to adsorb/desorb oxygen-containing intermediates and thereby improving the intrinsic activity of NiFe-MOF. By combining material characterizations and DFT calculation, a series of NiM-MOF (M = Fe, Co, Mn, Cu, or Zn) nanosheet arrays have been synthesized as a platform to elucidate and verify the specific roles of Fe in NiFe-MOF towards alkaline OER. [Display omitted] • NiM-MOFs (M = Fe, Co, Mn, Cu, or Zn) nanosheet arrays were synthesized as OER catalysts. • Fe incorporation optimized the crystallinity and electronic structure of the NiFe-MOF. • DFT was used to elucidate and verify the specific role of Fe in NiFe-MOF towards OER. [ABSTRACT FROM AUTHOR]

[Display omitted] Electron–phonon interactions and electron–electron correlations represent two crucial facets of condensed matter physics. For instance, in a half-filled spin-1/2 anti-ferromagnetic chain, the lattice dimerization induced by electron-nucleus interaction can be intensified by onsite Coulomb repulsion, resulting in a spin-Peierls state. Through first-principles calculations and crystal structure prediction methods, we have identified that under mild pressures, potassium and ammonia can form stable compounds: R 3 ¯ m K(NH 3) 2 , Pm 3 ¯ m K(NH 3) 2 , and Cm K 2 (NH 3) 3. Our predictions suggest that the R 3 ¯ m K(NH 3) 2 exhibits electride characteristics, marked by the formation of interstitial anionic electrons (IAEs) in the interlayer space. These IAEs are arranged in quasi-two-dimensional triangular arrays. With increasing pressure, the electronic van-Hove singularity shifts toward the Fermi level, resulting in an augmented density of states and the onset of both Peierls and magnetic instabilities. Analyzing these instabilities, we determine that the ground state of the R 3 ¯ m K(NH 3) 2 is the dimerized P 2 1 / m phase with zigzag-type anti-ferromagnetic IAEs. This state can be described by the triangular-lattice antiferromagnetic Heisenberg model with modulated magnetic interactions. Furthermore, we unveil the coexistence and positive interplay between magnetic and Peierls instability, constituting a scenario of spin-Peierls instability unprecedented in realistic 2D materials, particularly involving IAEs. This work provides valuable insights into the coupling of IAEs with the adjacent lattice and their spin correlations in quantum materials. [ABSTRACT FROM AUTHOR]

Hollow cubic nanoheterojunction in SnS 2 /CdS is obtained via in situ sulfuration-hydrothermal-chemical deposition. The SnS 2 /CdS nanoheterojunction (SnS 2 /CdS-3) exhibits remarkable enhanced photocatalytic HER (∼1424.56 μmol g−1 h−1) and photodegradation than normal CdS (∼72/∼28 folds) and SnS 2 (∼148/∼29 folds). In this structure, the SnS 2 /CdS heterojunction with greater Fermi levels gradient can promote interface carrier drive to optimize carrier efficiency, the hollow cubic structure can provide numerous active sites to decreased overpotential and promote electron diffusion, and increase light reflections, including inhibiting photocorrosion and maintaining structural stability. [Display omitted] • Heterojuction with greater Fermi levels gradient can optimize carrier efficiency. • Hollow cubic structure can increase active sites to promote electron diffusion. • Hollow cubic structure can shorten carrier pathway to inhibit photocorrosion. [ABSTRACT FROM AUTHOR]

[Display omitted] The reactivity of metal surfaces is a cornerstone concept in chemistry, as metals have long been used as catalysts to accelerate chemical reactions. Although fundamentally important, the reactivity of metal surfaces has hitherto not been explicitly defined. For example, in order to compare the activity of two metal surfaces, a particular probe adsorbate, such as O, H, or CO, has to be specified, as comparisons may vary from probe to probe. Here we report that the metal surfaces actually have their own intrinsic/eigen reactivity, independent of any probe adsorbate. By employing unsupervised machine learning algorithms, specifically, principal component analysis (PCA), two dominant eigenvectors emerged from the binding strength dataset formed by 10 commonly used probes on 48 typical metal surfaces. According to their chemical characteristics revealed by vector decomposition, these two eigenvectors can be defined as the covalent reactivity and the ionic reactivity, respectively. Whereas the ionic reactivity turns out to be related to the work function of the metal surface, the covalent reactivity cannot be indexed by simple physical properties, but appears to be roughly connected with the valence-electron number normalized density of states at the Fermi level. Our findings expose that the metal surface reactivity is essentially a two-dimensional vector rather than a scalar, opening new horizons for understanding interactions at the metal surface. [ABSTRACT FROM AUTHOR]

In this article, we constructed an AlN/B 2 SSe heterostructure using B 2 SSe and AlN. Using first-principles calculations, we calculated the stability, electronic structure, optical properties, and photocatalytic properties of the AlN/B 2 SSe heterostructure. Firstly, we consider four high-symmetry stacking configurations of the AlN/B 2 SSe heterostructure: Model I, Model II, Model III, and Model IV. After analysis, Model III and Model IV have the lower binding energy. The stability of the Model III and Model IV of AlN/B 2 SSe heterostructure was determined through phonon spectra. Secondly, the band structure, charge density, work function, and difference charge density of the AlN/B 2 SSe heterostructure were calculated using the HSE06 hybrid density functional. Model III is an indirect bandgap semiconductor with a bandgap of 1.89/3.03 eV at the PBE/HSE06 level, meanwhile, Model IV is also an indirect bandgap semiconductor with a bandgap of 1.47/2.60 eV at the PBE/HSE06 level. The work functions (Φ) of B 2 SSe, AlN, Model III, and Model IV are 6.31 eV, 5.81 eV, 6.02 eV, and 6.08 eV, respectively. This also means that during the heterojunction formation between B 2 SSe and AlN, electrons will transfer from the AlN layer to the B 2 SSe layer until the Fermi level reaches dynamic equilibrium, which creates a built-in electric field between the B 2 SSe and AlN layers. The presence of the built-in electric field promotes the separation of electron-hole pairs. Additionally, applying strain to the AlN/B 2 SSe heterostructure further broadened the range of the optical absorption spectrum. The light absorption range of Model III is extended to 557 nm, and the light absorption range of Model IV is extended to 683 nm. Therefore, the photocatalytic efficiency of AlN/B 2 SSe heterostructure is improved under strain. Finally, the AlN/B 2 SSe heterostructure exhibited good hydrogen evolution efficiency, as observed through HER. These characteristics make the AlN/B 2 SSe heterostructure promising for photocatalytic water-splitting applications. • The structural, optical, mechanical, and electronic properties of the AlN/B 2 SSe heterostructure were studied. • From indirect band gap to direct band gap and then indirect band gap of AlN/B 2 SSe heterostructure under strain. • The band gap first increased and then decreased of AlN/B 2 SSe heterostructure. • Strain can modulate the electronic and optical properties effectively. [ABSTRACT FROM AUTHOR]

Hydrogen has recently attracted a lot of attention as a clean as well as sustainable energy source. However, the vast bulk of industrial hydrogen is produced by converting natural gas into hydrogen. One of the primary goals of large-scale electrolysis is to find efficient, cost-effective, stable, and many other catalysts capable of producing hydrogen from water with minimal electrical bias. Using readily available electrocatalysts on Earth to facilitate the oxidation of water is one way to get closer to an effective method of splitting water to produce hydrogen. Here in the present work, CuWO 4 was coated on the conducting polypyrrole (PPy) polymer via hydrothermal techniques to boost its catalytic performance. The fabricated PPy/CuWO 4 composite is then utilized for water splitting to yield hydrogen in addition to oxygen. The PPy is able to raise the CuWO 4 Fermi levels are separated, as a result, the PPy/CuWO 4 produced a large number of strong and readily accessible charges, which led to the splitting of water into hydrogen, and demonstrated that at a potential of 1.470 V vs. RHE, the current density intended for CuWO 4 -3/PPY reached 10 mAcm−2, attaining an overpotential of 197 mV, with a Tafel plot slope of about 34.4 mVdec−1, and also with a charge transfer resistance of 2.3Ω for OER. Furthermore, the HER activity also attained lower overpotential (250 mV), with a Tafel slope of 50 mV dec−1 in order to reach a 10 mAcm−2 current density. In addition, the CuWO 4 is completely encased by the PPy, facilitating charge transfer, allowing the particles to travel rapidly to the polymer's surface. Hence, this study demonstrates that the highly effective CuWO 4 -3/PPy nanocomposite is responsible for future energy-related applications. [Display omitted] • The PPy/CuWO 4 is fabricated via hydrothermal technique for hydrogen production. • The fabricated PPy/CuWO 4 composite demonstrates a potential of 1.470 V vs. RHE. • The CuWO 4 -3/PPY attains tafel slope of 34.4 mVdec−1 at 10 mAcm−2. • It also attained lower overpotential 250 mV at 10 mAcm−2 for HER. • The CuWO 4 -3/PPy nanocomposite shows many future energy related applications. [ABSTRACT FROM AUTHOR]

Improving chemical stability and performance is desirable for protonic ceramic cathodes (PCFCs). In this study, the proton conductor SrSn 0.8 Sc 0.2 O 3-δ (SSSc) is used to couple the classically unstable Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathode to increase the chemical stability of the composite cathode. Compared to the conventional BSCF + BaCe 0.7 Zr 0.1 Y 0.2 O 3-δ (BCZY) composite cathode, the new BSCF + SSSc cathode demonstrates enhanced chemical stability. This is a result of the superior chemical stability of SSSc, which protects BSCF. Moreover, the formation of oxygen vacancies is easier at the BSCF/SSSc interface than at the BSCF/BCZY interface, thereby enhancing the cathode oxygen reduction reaction (ORR) activity. The closer proximity of the O p-band center to the Fermi level in BSCF + SSSc compared to BSCF + BCZY further validates the higher ORR activity of the BSCF + SSSc cathode. The peak power density of the PCFC with BSCF + SSSc cathode, which reaches 1404 mW cm−2 at 700 °C, is significantly greater than that with BSCF + BCZY cathode. The protection of SSSc to BSCF is also reflected in the fuel cell's long-term operation, as the BSCF + SSSc cell operates without detectable degradations for more than 150 h, whereas the BSCF + BCZY cell exhibits observable degradation. These findings indicate that utilizing the SSSc proton conductor to couple the cathode material is a feasible and effective strategy for producing the composite cathode with high chemical stability and superior electrochemical performance for PCFCs. [ABSTRACT FROM AUTHOR]

To explore the correlation between the hydrogen concentration and electronic properties of the lithium borohydrides (LiBH x), we apply the first-principles method to study the influence of hydrogen (H) concentration on the structural stability, physical properties and hydrogen storage properties of LiBH x (x = 1 and 4). Two hydrogen concentrations are considered. The calculated results show that three LiBH x phases are thermodynamic stability because of the negative formation enthalpy. LiBH with the low concentration of hydrogen has better thermodynamic stability in comparison to LiBH 4. In particular, the calculated gravimetric hydrogen storage capacity is 5.06 wt% for LiBH and 15.53 wt% for LiBH 4 , respectively. Essentially, the higher hydrogen storage capacity of LiBH 4 is related to the product of [BH 4 ] group because of the strong electronic interaction between B atom and H atom. Based on the m -GGA function, it is found that the calculated band gap is 0.044 for LiBH, 7.744 eV for the hexagonal LiBH 4 and 7.908 eV for the orthorhombic LiBH 4 , respectively. Naturally, the calculated electronic structure shows that the wide band gap is related to the band separation between H-s state, Li-state and B-2 p state near the Fermi level. [ABSTRACT FROM AUTHOR]

Solar energy is considered a sustainable energy resource for various electrochemical reactions, but its conversion efficacy is controlled by excitons transference and isolation. To increase the conversion efficacy, it is vital to restrict the recombination rate of photocarriers and boost their redox potentials. For this, S-scheme-based photocatalysts offer an effective charge migration mechanism. Herein, we have highlighted the basics of the electronic and optical properties of CdS as a potential photocatalyst using DFT simulation. Afterward, an overview of the thermodynamic kinetics for PWS has been defined. The high point of the review is the CdS-based S-scheme charge transferal route comprising of a reductive and oxidative photocatalyst having staggered band alignment with a difference in Fermi energy level for H 2 evolution. Also, the factors determining the S-scheme charge transferal route with respective validating techniques, like in/ex -situ XPS analysis, EPR, AFM, and DFT theoretical simulations, have been discussed. These characterization techniques successfully validated the S-scheme mechanism. Lastly, shortcomings of CdS-based S-scheme heterostructures that further need to be examined in this promising research arena have been outlined. [Display omitted] • Recent advances in the electronic and optical properties of CdS are revealed. • Mechanistic insights on the emergence of S-scheme mechanisms have been explored. • Various validation techniques for CdS-based S-scheme charge transferal route are delineated. • A concluding remark and future viewpoints on the CdS-based S-scheme are proposed. [ABSTRACT FROM AUTHOR]

The kinetic of the oxygen reduction reaction (ORR) at the cathodes of polymer-electrolyte-membrane fuel cells (PEMFCs) has been demonstrated to be slow, which is one of the pivotal issues in developing PEMFCs. Within the current piece of research, by performing first-principles calculations, we introduce a Co-doped vacancy BN nanosheet (Co-HBN) as an efficacious noble metal-free electro-catalyst for the ORR process (ORRP) in fuel cells. The results demonstrate a rise in the energies of adsorption (or adhesion) onto the Co–N active site of these electrocatalysts in the order of O < OH < OOH < O 2 < H 2 O 2 < H 2 O on this electrocatalyst and there is a consistent change in the adsorption energies (E ads)for all oxygen-containing intermediates (OCIs). Based on the small and large thermodynamic driving force for the generation of H 2 O 2 and for reducing OOH into O∗ (or to 2OH∗), respectively, the four-electron route was more favorable in comparison with the 2e− route. Furthermore, with the largest value of ΔG for Co-HBN electrocatalyst, the final reduction step (OH∗ + H+ + e− → H 2 O + ∗) has been regarded as the rate-limiting step. The d-band center of Co was considerably distant from the Fermi level. The greater gap between the frontier orbitals suggested that the electrocatalyst is not conducive to the adsorption of OCIs, which shows that the onset potential is larger and ORR is high. • The catalytic activity of a series of Co-doped v-BN has been theoretically explored in the ORR. • O 2 molecule can be directly dissociated on the Co-doped v-BN with 4e pathway. • It is reacting more favorable for the ER mechanism of OH∗ to convert into H 2 O. • The ORR reaction was found to be thermodynamically favorable in the Co-doped v-BN. [ABSTRACT FROM AUTHOR]

The design of reasonable and efficient electrocatalysts is imperative in large scale water splitting applications. In this paper, NiMoO 4 nanospheres doped with Cr and P were constructed by hydrothermal method and phosphating process as electrocatalysts for water splitting, and the doping of Cr and P effectively modulated the electronic structure, which led to an increase in the active sites and an increase in the intrinsic activity of each site. Notably, Cr/P–NiMoO 4 @NF presented excellent urea oxidation reaction (UOR) performance (1.312V @ 10 mA cm−2) and oxygen evolution reaction (OER) performance (overpotential 309 mV @ 10 mA cm−2) in electrolytes of 1 M KOH and 1 M KOH with 0.5 M urea because of the doping effect of Cr and P. The experimental analysis showed that the improvement of electrochemical performance was mainly reflected in the accelerated electron transfer rate, increased exposure of reaction sites and improved metal properties and so on. For Cr/P–NiMoO 4 @NF, after a long time UOR and OER stability test, some changes have taken place in the appearance of the sample, which increases the contact area and provides more active sites, making the catalytic performance of the sample have no too obvious attenuation. Density functional theory calculation shows that the Cr/P–NiMoO 4 material exhibits higher urea adsorption energy, indicating that urea is preferentially adsorbed on its surface. The Cr/P–NiMoO 4 material shows more state density near the Fermi level, indicating that the introduction of Cr and P enhances the conductivity of the Cr/P–NiMoO 4 material. This work provides a novel idea for the research and exploitation of low cost and robust UOR and OER electrocatalysts. [Display omitted] • NiMoO 4 nanospheres doped with Cr and P were constructed by hydrothermal method. • Cr/P–NiMoO 4 @NF presented excellent urea oxidation reaction performance (1.312V @ 10 mA cm−2). • Cr/P–NiMoO 4 @NF presented excellent oxygen evolution reaction performance (overpotential 309 mV @ 10 mA cm−2). [ABSTRACT FROM AUTHOR]

In this paper, the crystal structure and electronic structure of Ti 4 O 7 were calculated based on density functional theory, and Magnéli phase Ti 4 O 7 bulks were successfully prepared by spark plasma sintering (SPS). Results indicated that the contribution of Ti 3 d to Fermi level increased due to the lack of oxygen atom in lattice, and the energy band gap of Ti 4 O 7 was reduced compared with that of TiO 2. By calculating the relationship between the densification rate and effective stress in the process of SPS, it can be known that the densification mechanism of Ti 4 O 7 powders was controlled by diffusion. Based on this, under the conditions of sintering temperature of 1000 °C, holding time of 10 min and sintering pressure of 30 MPa, Ti 4 O 7 bulks with the optimal electrical conductivity (961.5 S cm−1) could be obtained, which was more than 30% higher than the graphite material reported in literature. The results reveals that Ti 4 O 7 will be one of the most promising electrode materials in the electrochemical field. [ABSTRACT FROM AUTHOR]

The off-stoichiometry i.e., ZrNi 1+δ Sn (0 < δ < 1), and carrier modulation are the two approaches that have separately been found effective mainly to reduce thermal conductivity and improve power factor. This work explores the combined effect of both of these approaches by tuning the carrier density by varying the Sb-concentration in off-stoichiometric ZrNi 1.04 Sn, which shifts the Fermi level towards the conduction band as confirmed by the band structure calculations. The maximum thermoelectric figure-of-merit ZT∼0.95 at ∼873 K was achieved in the optimum composition ZrNi 1.04 Sn 0.975 Sb 0.025. For evaluating the device applicability of the synthesized materials, the cumulative temperature dependence (CTD) model was applied, predicting the single leg maximum efficiency ∼8.6% at ΔT ∼ 546 K. A series of calculations have been performed to predict electronic band structure and electronic transport properties to unearth the underlying physics. The microhardness and fracture toughness were determined to ensure that the enhanced thermoelectric performance is not deteriorating mechanical robustness. [ABSTRACT FROM AUTHOR]

Unprecedented standalone tandem cell consisted of dual Cu 2 O, of which the complementary wavelength–dependent quantum efficiency is in favor of the full utilization of the broadband sunlight with the photon energy above their characteristic band gap and the striking difference in the Fermi level as a result of their distinct p –type and n –type conductivities turns into a strong photovoltage, is developed in the present contribution to carry out unassisted photoelectrochemical water splitting using energy exclusively from the sun. Further deposition of the n –type TiO x overlayer on p –type Cu 2 O engineered into a wire–like nanostructure, forming the core–shell p – n heterojunction to provide additional photovoltage to accelerate the hydrogen evolution reaction, and the circumvention of the severe charge accumulation at the Schottky Cu/ n –Cu 2 O back contact well relax the associated kinetic overpotentials. The synergistic effect renders the solar–to–hydrogen efficiency of the tandem n –TiO x / p –Cu 2 O// n –Cu 2 O device amounting to 0.32%, which is among the highest performance reported to date for the Cu 2 O–based tandem PEC//PEC cells in the literature. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Catalytic descriptors of electrocatalysts such as d -band center are the important indicators that connect the physiochemical interaction and catalytic performance and have been used for rational design of the catalysts and performance optimizations. However, these descriptors developed in traditional electrocatalysts are invalid in recent emerged topological catalysis. Here, we identify topological surface state (TSS) density at the Fermi level can serve as the universal catalytic descriptor in the family of metal diborides, the materials hosting fantasying topological nodal-net states. The catalytic activity for hydrogen evolution reaction (HER) is linearly correlated with the projected TSSs on corresponding surfaces, which are independent on the material types. The findings are further proven by the weakened HER performance under topological phase transition where the TSS density at Fermi level is reduced, and the revival of d -band center once all the TSSs are removed. Our work will open a new route for developing high-performance catalysts from the quantum topological point of view. [ABSTRACT FROM AUTHOR]

Pb 0.92 La 0.08 (Zr 0.52 Ti 0.48)O 3 / YBa 2 Cu 3 O 7− ẟ (PLZT/YBCO) heterostructure was prepared via the photosensitive sol–gel method (P-SG) combined with pulsed laser deposition (PLD). Test results show that the preparation process of PLZT film does not significantly cause degradation of the superconductivity of underlying YBCO film, and the PLZT has good ferroelectric properties in the temperature range of 300–50 K. With decreasing temperature, ferroelectric domain formation and inversion become more difficult, which causes coercive field (E c) of PLZT to increase. However, remanent polarization (P r) remains almost constant with decreasing temperature. Furthermore, it is found that the critical transition temperature (T c) of YBCO decreases and resistance of non-superconducting state of YBCO increases as positive electric field applied to PLZT increases, while T c and the resistance of non-superconducting state of YBCO do not change when negative electric fields are applied. It is believed that polarization charges regulate Fermi level of PLZT, which results in the promotion (hindrance) of electron injection into YBCO for positive (negative) applied electric fields, thereby regulating T c and the resistance of non-superconducting state of YBCO. When positive applied electric fields are removed, the superconducting properties of YBCO in PLZT/YBCO structure cannot be restored to their initial values due to the remanent polarization of PLZT. [ABSTRACT FROM AUTHOR]

A CuAlO 2 /LaNiO 3 quantum dots/SnO 2 transparent pn junction is prepared by a sol-gel-annealing-hydrothermal method. The obtained CuAlO 2 /LaNiO 3 QDs/SnO 2 exhibits a high transmittance of ∼90%, obvious photovoltaic enhancement of ∼3.0 × 103-fold compared to intrinsic CuAlO 2 /SnO 2 (PCE of ∼1.03%), and stable output during 3000 s and 6 months of cycling. This is mainly ascribed to the dual functional perovskite LaNiO 3 QDs, which obtain an appropriate Fermi level and high quantum yields and can optimize the carrier kinetic equilibrium efficiently while maintaining higher transparency. Moreover, the p-type carrier induction of Cu vacancies, interstitial oxygen and Ni2+/Ni3+ ions can further optimize the carrier efficiency. Additionally, CuAlO 2 and SnO 2 with stable intrinsic physical-chemical properties can efficiently increase the photovoltaic conversion stability. [ABSTRACT FROM AUTHOR]

[Display omitted] The itinerant ferromagnetism can be induced by a van Hove singularity (VHS) with a divergent density of states at Fermi level. Utilizing the giant magnified dielectric constant ε r of SrTiO 3 (111) substrate with cooling, here we successfully manipulated the VHS in the epitaxial monolayer (ML) 1T-VSe 2 film approaching to Fermi level via the large interfacial charge transfer, and thus induced a two-dimensional (2D) itinerant ferromagnetic state below 3.3 K. Combining the direct characterization of the VHS structure via angle-resolved photoemission spectroscopy (ARPES), together with the theoretical analysis, we ascribe the manipulation of VHS to the physical origin of the itinerant ferromagnetic state in ML 1T-VSe 2. Therefore, we further demonstrated that the ferromagnetic state in the 2D system can be controlled through manipulating the VHS by engineering the film thickness or replacing the substrate. Our findings clearly evidence that the VHS can serve as an effective manipulating degree of freedom for the itinerant ferromagnetic state, expanding the application potentials of 2D magnets for the next-generation information technology. [ABSTRACT FROM AUTHOR]

Kesterite Cu 2 ZnSnS 4 (CZTS) thin film is an attractive photovoltaic material. Harmful vacancy and anti-site defects in CZTS can be reduced by equivalent doping. However, equivalent doping leads to a reduction in the carrier concentration that is essential to the built-in electric field and built-in potential of the device. In this work, we propose heterovalent Al doping to provide hole conduction in CZTS thin film. The chemical valence of doping cation Al3+ is different from that of the substituted cation Sn4+. Al-doped CZTS thin films were fabricated by magnetron sputtering and sulfurization. The Al content was controlled by the Al sputtering time of the precursor. The experimental results revealed the successful fabrication of heterovalent Al-doped CZTS with the preferred orientation of the (112) plane. The partial substitution of Sn by Al led to a right shift of the CZTS diffraction peaks. Al doping could improve the crystalline quality of CZTS, reduce the dislocation density and microstrain of CZTS, and enhance the compactness of the thin-film surface. With the increase in Al content, the distance decreased between the Fermi level and the valence band maximum of CZTS, and the hole concentration and conductivity of CZTS increased monotonously while the non-radiative recombination of carriers was suppressed. The conductivity of CZTS reached 1.47 × 102 S/cm. Therefore, heterovalent Al doping was found to be a useful method to regulate the electrical properties of CZTS thin film. [ABSTRACT FROM AUTHOR]

The combination of photothermal treatment and chemodynamic therapy has attracted extensive attention for improving therapeutic effects and compensating the insufficiency of monotherapy. In this work, a copper-metal organic framework (Cu-BTC) was used to augment the photothermal effect of polydopamine (PDA) and endow it with a chemodynamic ability by constructing a Cu-BTC@PDA nanocomposite. Density functional theory calculations revealed that the plasmonic vibrations formed by the d-d transition of Cu at the Fermi level in Cu-BTC@PDA could enhance the photothermal performance of PDA. In addition, more Cu2+ released from Cu-BTC@PDA in the acidic microenvironment of the tumor was then reduced to Cu+ by glutathione (GSH) and further catalyzed H 2 O 2 to generate more toxic hydroxyl radical (•OH), which synergized with photothermal treatment for melanoma therapy. Furthermore, Cu-BTC@PDA could quickly and effectively kill bacteria under the action of PTT, and the sustained release of Cu ions could contribute to the long-term and stable bacteriostatic ability of the material. This sustained release of Cu ions could also promote the cell migration and angiogenesis, and upregulate the expression of COL -, TGF -, and VEGF -related genes to accelerate wound healing. This multifunctional nanomaterial has potential application in the treatment of melanoma and repair of wounds. We constructed a multifunctional nanoplatform (Cu-BTC@PDA) by two steps. This nanoplatform can not only perform cascade catalysis in the tumor microenvironment to generate more toxic hydroxyl radical (•OH), but also synergize with photothermal treatment for melanoma therapy. Additionally, Cu-BTC@PDA possesses enhanced photothermal performance through the plasmonic vibrations formed by the d-d transition of Cu at the Fermi level in Cu-BTC@PDA, which is revealed by DFT calculations. And Cu-BTC@PDA shows good antitumor, antibacterial, and wound healing properties in vivo and in vitro. Such a multifunctional nanomaterial has potential application in the treatment of melanoma and repair of wounds. [Display omitted] [ABSTRACT FROM AUTHOR]

The induced impacts of high doses of gamma irradiations on the optical features of the Makrofol DE 1-1 detector were studied in the ultraviolet and visible range (from 270 to 500 nm). Makrofol DE 1-1 detector specimens were irradiated separately for different doses from 200 to 1000 kGy; step 200. The optical absorbance spectra of the pristine Makrofol DE 1-1, as well as the irradiated gamma-ray samples display two main features: (i) A redshift with further gamma-ray irradiation doses from 200 to 1000 kGy. This redshift can be ascribed to irradiation-induced defects in polymer material. (ii) A remarkable increment in the optical absorbance for irradiated Makrofol DE 1-1 specimens compared to the pristine one. This increment can be ascribed to the creation of some electronic levels within the forbidden gap resulting from the irradiation process. Moreover, this absorbance increment was employed to assess the degradation percent produced by gamma-ray irradiations. The degradation percent of the Makrofol DE 1-1 increased from 31.73% at 200 kGy to 78.08% at 1000 kGy. The optical band gap, Fermi level and metallization criterion showed decrement behaviors with further doses of gamma-ray irradiations. Also, the percent of changes in optical band gap values were employed to evaluate the degradation of Makrofol DE 1-1 under gamma-ray irradiations. This percent augmented from 15.19% at 200 kGy to 20.25% at 1000 kGy proving the obvious degradation of Makrofol DE 1-1 under gamma-ray irradiations. On the other hand, the number of carbon atoms per cluster, linear and nonlinear refractive indices showed increasing behaviors with further doses of gamma-ray irradiations. [ABSTRACT FROM AUTHOR]

Fabrication of ordered structures at the nanoscale limit poses a cornerstone challenge for modern technologies. In this work we show how naturally occurring moiré patterns in Ir(111)-supported graphene template the formation of 2D ordered arrays of substitutional boron species. A complementary experimental and theoretical approach provides a comprehensive description of the boron species distribution, bonding configurations, interfacial interaction with Ir(111) and the impact on graphene's electronic structure. Atomically-resolved scanning tunnelling microscopy images and density functional theory calculations reveal that boron preferably forms small aggregates of substitutional defects in geometrically low regions of the moiré superlattice of graphene, by inducing local bending of graphene towards the underlying Ir(111). Surprisingly, calculations reveal that the incorporation of electron deficient boron does not lead to an enhanced p-type doping, as the local rippling of the graphene layer prompts electron uptake from the iridium substrate that compensates the initial electron loss due to substitutional boron. Scanning tunnelling spectroscopy and angle-resolved photoemission spectroscopy measurements corroborate that the arrays of boron species do not modify the electronic structure of graphene near the Fermi level, hence preserving the slight p-type doping induced by Ir(111). [Display omitted] [ABSTRACT FROM AUTHOR]

Finding efficient and versatile catalysts that can both produce clean energy H 2 and treat wastewater is an important matter to solve energy shortages and wastewater pollution. Herein, a feather-like NiCoP supported on NF was synthesized via the two-step hydrothermal-phosphorization process. NiCoP/NF requires only overpotentials of 44 and 203 mV to reach 10 mA cm−2 for HER and OER in 1 M KOH, respectively. Besides, NiCoP/NF requires only 1.13 V (vs RHE) to achieve 10 mA cm−2 in 1 M KOH containing 0.33 M urea. DFT calculation shows that NiCoP exhibits enhanced DOS in the Fermi level attachment, which promotes charge transfer. Subsequently, the trifunctional NiCoP/NF, for overall water splitting, requires a lower potential of 1.48 V to gain 10 mA cm−2 in 1 M KOH. For urea electrolysis, NiCoP/NF requires just 1.36 V to drive 10 mA cm−2 in 1 M KOH with 0.33 M urea. This work provides extraordinary insights into electrolytic hydrogen production and wastewater treatment through simple preparative methods. The performance of the prepared catalyst is at a high level in non-noble metal. [ABSTRACT FROM AUTHOR]

High-strain-induced microstructural refinement and dislocations are critical for the strengthening of metallic materials; however, this is difficult to achieve in ceramic materials due to their unique bonding characteristics and electronic structure. Here, a series of β -Mo 2 C bulk ceramics are consolidated by the high pressure and high temperature (HPHT) strategy. Our results demonstrate that high strain-induced grain plastic deformation at high pressure produces a lamellar sub-grain structure with high-density dislocations, and that the dislocations at the lath-like grain boundaries eventually evolve into low-angle grain boundaries. The mechanical properties, superconducting behavior, and onset of oxidation of the specimens are investigated. It is found that superconductivity and hardness arise from the high density of states at the Fermi level, while the high intrinsic hardness is attributed to the strong hybridization between Mo-4 d orbitals and C-2 p orbitals. Furthermore, strain-induced defect structure (dislocations and low-angle grain boundaries) mainly mainly enhances the intrinsic structure of β-Mo 2 C. [ABSTRACT FROM AUTHOR]

One of the holy grails of catalysis - direct nonoxidative methane conversion to ethylene is resolved in this study using dielectric barrier discharge plasma (DBDP) assisted catalysis. Motivated by the formation of ethane and very low amount of ethylene in the DBDP over acid or base treated kaolin supported Ni and oxalate ligand functionalized Ni in CO 2 reforming of methane wherein Ni catalysts that were calcined at 800 °C showing higher methane conversion ( X CH4), ethylene to ethane (C 2 = /C 2 –) ratio, and hydrogen yield ( Y H2). A novel CeO 2 confined atomically dispersed Pt supported on oxalate ligand functionalized Cu modified zeolite Y catalyst (PtCe/CuX-ZY) was synthesized to exhibit strong-metal-support interaction, which rendered the d-band center far away from the Fermi level, densification, and localization of d electrons thus weakening the adsorption of C 2 H 4 upon formation to prevent subsequent hydrogenation to ethane. The novel PtCe/CuX-ZY catalyst showed an impressively high average X CH4 , Y C2H4 , and Y H2 of 73.5%, 23.9%, and 33.8%, respectively with a high C 2 = /C 2 – ratio of ca. 12.3 compared to an average of 0.032 observed over Ni-based catalysts. This finding is impressive and opened up a further investigation in both academia and the industry. [Display omitted] • High ethylene selective Pt-based nanocomposite catalyst was synthesized. • Pt-based nanocomposite catalyst converted methane to ethylene and hydrogen. • Shift in Pt d-band center away from Fermi level favours ethylene yield. • Non-catalytic plasma activation of methane favour ethane. • Catalytic plasma activation of methane favour ethylene and hydrogen. [ABSTRACT FROM AUTHOR]

Perovskite oxides (ABO 3−δ) have highly tuneable compositions because of the abundance of element candidates for the A-, B-, and O-sites. Generally, perovskite catalytic activity for the oxygen evolution reaction (OER) can be improved by B-site doping. However, doping does not always enhance activity. This work shows that Nb doping of La 0.2 Sr 0.8 CoO 3−δ (LSC) is detrimental to OER activity but benefits cycling stability. With 10 at.% Nb doping (La 0.2 Sr 0.8 Co 0.9 Nb 0.1 O 3−δ , LSCN10), the overpotential at 10 mA cm−2 increased to 450 mV, 30 mV higher than that of the undoped LSC. Accelerated stability testing demonstrated enhanced stability with only 5 mV attenuation after 1000 cycles. Density functional theory (DFT) revealed that the high stability stems from the downward shift of the O 2 p band centre relative to the Fermi level. The findings of this work provide guidance for the design of highly stable OER perovskite catalysts. [ABSTRACT FROM AUTHOR]

The construction of efficient and low-cost photocatalytic systems is a major challenge in the field of photocatalysis. An efficient heterojunction photocatalyst designed for water splitting is also an interesting prospect in energy conversion. In this study, a novel Mn 0.43 Cd 0.57 S/ZnCo 2 O 4 p-n heterojunction photocatalyst was prepared via a simple solvothermal method. Mn 0.43 Cd 0.57 S was loaded on the surface the of noble metal-free transition metal oxide ZnCo 2 O 4 to prevent the agglomeration of particles, resulting in efficiently improving the photocatalytic performance of the material. Due to the Fermi level balance, the band bending of the two materials constructs a p-n heterojunction, which stimulates the transfer of photogenerated electrons from the CB of Mn 0.43 Cd 0.57 S to the CB of ZnCo 2 O 4. The uniformly dispersed p-n heterojunction structure effectively suppresses the recombination of photoinduced charges and preserves stronger redox charges. As a result, the established Mn 0.43 Cd 0.57 S/ZnCo 2 O 4 heterojunction showed the best photocatalytic hydrogen production concentration (92.1 mmol g−1 h−1), which was 4.7 times that of the original Mn 0.43 Cd 0.57 S (19.4 mmol g−1 h−1) and 54.2 times that of ZnCo 2 O 4 (1.7 mmol g−1 h−1). This strategy will provide new insights into the development of new photocatalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphene/Cu composites are promising materials for future electrodes because of their mechanical, electrical, and thermal stability. However, the presence of graphene accelerates oxidation of the underlying Cu surface, which affects the various properties of graphene/Cu composites. Therefore, investigating the effects of Cu oxidation on the interfacial properties of graphene/Cu composite is critical. Here, the time-dependent doping and strain of large-area graphene on a Cu surface were analyzed through characterization of both the degree of oxidation and the crystallographic orientation of Cu using Raman spectroscopy. Moreover, we proposed a model for describing the Fermi level of graphene depending on the state of the Cu, such as its crystallographic orientation and degree of surface oxidation. [Display omitted] [ABSTRACT FROM AUTHOR]

The strong interaction between graphene and elemental ferromagnetic transition metals results in considerable shifts of the graphene π band away from the Fermi level. At the same time, a weakly-dispersing single-spin conical band feature is found in the proximity of the Fermi level at the K ̄ point in the surface Brillouin zone of epitaxially-aligned graphene/Co(0001). Here, the robustness of this electronic state against twisting angles at the interface is experimentally and theoretically demonstrated by showing the presence of similar band features also in the case of rotated graphene domains on Co(0001). Spin-resolved reciprocal space maps show that the band feature in rotated graphene has similar Fermi velocity and spin polarization as its counterpart in epitaxially-aligned graphene. Density functional theory simulations carried out for the experimentally observed graphene orientations, reproduce the highly spin-polarized conical band feature at the graphene K ̄ point, characterized by a hybrid π -d orbital character. The presence of the conical features in the rotated domains is attributed to the unfolding of the superstructure K ̄ point states exclusively to the K ̄ point of the graphene primitive cell. The similarities found in the electronic character for different graphene orientations are crucial in understanding the magnetic properties of realistic graphene/Co interfaces, facilitating their implementation in spintronics applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, we synthesize V5+-doped LiNi 0.5 Mn 1.5 O 4 (LNMO) and subject it to SiO 2 surface modification using a coprecipitation method. The synergistic effect of ion doping and interfacial engineering improves the electrochemical properties of LNMO by accelerating its redox kinetics and prolonging its cycling life. The experimental results and density functional theory simulation data indicate that V5+-ion doping caused the Fermi level of LNMO to shift toward the conduction band, thereby narrowing the bandgap of LNMO because of the n-type doping effect. However, the introduction of V5+ ions prevents Li + -ion migration in LNMO, which hinders the ion intercalation–deintercalation process of LNMO cathodes. Therefore, the V5+-doped LNMO compound with optimal V5+-ion doping concentration was expected to present the highest rate capability. In addition, SiO2 surface modification provides a protective layer that inhibits metal dissolutions and significantly improves cathode cycling stability. Owing to the synergistic effect of doping and interfacial modification, the fabricated LNMO cathode presented remarkable energy storage capacity with discharge capacities of 133/118.8 mAh/g at 0.2/10 C and a capacity retention of 87.9% after 200 cycles at 4 C. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting is an emerging technology for the development of maintainable hydrogen energy. It remains challenging to manufacture a stable, efficient, and cost-effective electrocatalyst that can conquer the slow reaction kinetics of water electrolysis. Herein, A metal-organic framework (MOF) based material is manufactured and productively catalyze the oxygen evolution reaction (OER). The introduction of elemental nickel enhances the catalytic activity of Co-FcDA. The results show that single Ni was well doped in the CoNi-FcDA catalysts and the doping of Ni has a great influence on the OER activity of CoNi-FcDA catalysts. CoNi-FcDA displayed a low overpotential of 241 mV to arrive at the benchmark current density (10 mA cm−2) with a remarkably small Tafel slope of 78.63 mV dec−1. It surpassed the state-of-the-art electrocatalyst for OER, that is, RuO 2 (260 mV and 97.26 mV dec−1) in efficiency as well as instability. Density functional theory (DFT) calculations show that suitable Ni doping at the same time can increase the density of states of the Fermi level, resulting in excellent charge density and low intermediate adsorption energy. These discoveries provide a practical route for designing 2D polymetallic nanosheets to optimize catalytic OER performance. • Elemental Ni is doped and enhances the catalytic activity of Co-FcDA through one pot solvothermal reaction. • The OER overpotentials of CoNi-FcDA at 10 mA cm−2 only required 251 mV. • CoNi-FcDA increases the DOS of the Fermi level, which produce charge density and low intermediate adsorption energy. [ABSTRACT FROM AUTHOR]

We report the study of conductive polyaniline (PANI) chain embedded Ti-MOF functionalized with CoS as a cocatalyst for hydrogen evolution reaction (HER) application. The post synthetically modified hybrid photocatalyst PANI/Ti-MOF/CoS greatly influences the redox and e− − h+ separation process and exhibits an impressive rate of HER (∼1322 μmol h−1g−1), suppressing the pristine Ti-MOF (∼62 μmol h−1g−1) with apparent quantum yield (AQY) of ∼3.2 and transient current response of ∼46.4 μA cm−2. In this system, Ti-MOF provides the circulation of Ti3+ and Ti4+ to the reaction of photocatalytic H 2 generation, where the additional PANI and CoS amended the performance of H 2 production through electron enrichment and thereby improving the stability and integrity of Ti-MOF. The Electrochemical studies demonstrated increased photocurrent by interweaving Ti-MOF crystal with PANI through cation-π interaction thereby enhancing interface connection and then promoting electron transfers. The charge dynamics revealed the initial charge transfer from photoexcited PANI to encapsulated MOF framework to boost the photocatalytic performance of the system. Further, the electron movement at the Ti-MOF/CoS interface is investigated through work function and electrochemical potential of electrons (Fermi level). DFT results demonstrate the importance of CoS in improving the photocatalytic performance of hybrid Ti-MOF catalyst, which leads to superior catalytic behaviour. These results establish that the encapsulation of catalytic active sites inside MOFs with desirable energy band gaps would be an ideal choice for the production of solar fuels. [Display omitted] • Robust photocatalyst PANI/Ti-MOF/CoS is reported in water splitting. • The hybrid composite possesses enhanced visible light absorptions. • Impressive H 2 production rate 1322 μmol h−1 g−1 with a quantum efficiency of 3.2%. • The co-existence of Ti4+/Ti3+ in the photocatalyst favours high HER. • The combined experimental and theoretical studies support superior activities. [ABSTRACT FROM AUTHOR]

• Understand the selective contacts of silicon heterojunction solar cells through band alignment, Fermi level and barrier height. • Development of a new matric called contact strength for illumination dependent requirements on electrode work-function, doping and thickness of the doped/contact layer. • Calibrated the simulation models with experimental data for a wide range of illuminations (0.01 suns to 1 sun). • The developed model will provide deeper insight into the strategy of carrier selective contacts at various illuminations. Heterojunction carrier selective contacts for solar cells have gained great attention because of the ability of these contacts to efficiently collect majority carriers while hindering the recombination of minority carriers, thus resulting in the highest reported voltage among crystalline silicon technologies. The electrode work-function, doping and thickness of the doped layer remain the key parameters for governing the cell performance. Recently, we have studied the requirements for carrier selective contacts under various illumination levels and reported logarithmic dependence of these parameters. In this work, we define a new metric for describing the ability of a contact to collect the carriers and named it as contact strength. We have developed an analytical approach for contact strength of hole selective contacts which represents the requirements on doping, thickness of the contact layer, and electrode work-function for a given illumination. First, the numerical model is calibrated with the experimental data for a wide range of illumination (0.01 Sun – 1.0 Sun) and then simulations have been fitted with analytical model. For the selective contact layer, we observe that only the total charge, rather than thickness and doping individually, matters. The work-function of the top electrode also contributes strongly to contact strength and can in principle substitute doped layer. This insightful metric will guide the solar cell technologists to better understand the carrier selective contacts and to maximize the cell performance not only at standard test conditions (STC), but also at low light illuminations. [ABSTRACT FROM AUTHOR]

This work reports information on the transience of hole doping in epitaxial graphene devices when nitric acid is used as an adsorbent. Under vacuum conditions, desorption processes are monitored by electrical and spectroscopic means to extract the relevant timescales from the corresponding data. It is of vital importance to understand the reversible nature of hole doping because such device processing can be a suitable alternative to large-scale, metallic gating. Most measurements are performed post-exposure at room temperature, and, for some electrical transport measurements, at 1.5 K. Vacuum conditions are applied to many measurements to replicate the laboratory conditions under which devices using this doping method would be measured. The relevant timescales from transport measurements are compared with results from X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy measurements, with the latter performed at ambient conditions and accompanied by calculations of the spectra in the Reststrahlen band. [Display omitted] [ABSTRACT FROM AUTHOR]

We report thermopower and electrical resistance of valence-unstable CeNi 4 Cu and its non-magnetic analogue LaNi 4 Cu in the range of temperatures between 4 and 900 K. Based on experimental data we analyze the contributions of cerium f -states to the total thermopower, considering electronic transport properties of the crystal matrix in which the f -electron subsystem is located. We demonstrate that CeNi 4 Cu is a concentrated Kondo system with high Kondo temperature, Т К , of approximately 1300 K, where temperature behavior of thermoelectric power manifests combined effects of Kondo scattering on localized f -centers together with scattering associated with the presence of a narrow d -band near the Fermi level. We further discuss the features of the temperature stability of the position of the narrow peak (so-called Kondo resonance) in the density of states at the Fermi level. • CeNi 4 Cu is a concentrated Kondo system with high Kondo temperature, Т К ≈1300 K. • Peculiarities of thermopower behavior are due to the combined effect of spin fluctuations in Ce- and Ni-sublattices. • Thermoelectric power of CeNi4Cu in a wide range of temperatures is well described in the two-band model. • Detected temperature instability of the position Kondo resonance at the Fermi level at temperatures T > 300 K. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermoelectric properties of F4TCNQ-doped benzodithiophene-thienothiophene copolymers. • Partial or integer charge transfer states between the polymers and dopant. • Significant influence of polymer aggregation on polymer-dopant interaction. • Correlation between the nature of charge transfer states with thermoelectric parameters. Organic thermoelectric materials have been gaining increasing interest due to their capacity to convert waste heat into electricity. This study explores the impact of doping-induced charge transfer states on the thermoelectric properties of benzodithiophene-thieno[3,2-b]thiophene-based polymers (PBDTTT) doped with 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Detailed structural, optical, and electrical analyses were conducted on two specific polymers, PBDTTT:C (P1) and PBDTTT:EFT (P2). The investigation revealed distinct doping behaviors: P1 formed a partial charge transfer (PCT) complex, whereas P2 predominantly formed an integer charge transfer (ICT) complex. This distinction is attributed to the inherent structural differences and varying aggregation capabilities of the polymers. As a result, P2 exhibited enhanced electrical conductivity and a superior thermoelectric power factor compared to P1. This study emphasizes the critical role of polymer aggregation and charge-transfer mechanisms in optimizing the thermoelectric performance of conjugated polymers. It offers valuable insights for the development of efficient thermoelectric materials and the advancement of energy conversion technologies. [ABSTRACT FROM AUTHOR]

The internally formed Ov-ZAF with spatially separated Ov-ZAF can reduce 498.3 mg/g of U(VI) in 100 ppm uranium solution in 200 min with a reduction efficiency of 99.8 %. [Display omitted] • It has excellent solar photocatalytic reduction of uranium and antibacterial properties. • Homogeneous flower-like microspheres of O v -ZAF were synthesized. • Z- Scheme heterojunction structure promotes photogenerated carrier migration. • O v -ZAF surface energy band alignment promotes separation of electrons and holes. • This strategy opens up new ideas for the design of specific nanocatalysts. Designing an efficient reduction of soluble U(VI) to insoluble U(IV) is a challenge, and efficient electron-hole transfer efficiency is the key to the conversion of U(VI) to U(IV). Herein, defective transition metal sulfide (O v -ZAF) Z-Scheme tandem heterojunctions with spatial separation were synthesized using an in situ self-assembly method. O v -ZAF has excellent electron-hole separation, stabilized reactive active sites, and excellent visible light absorption. O v -ZAF is able to realize the photocatalytic U(VI) reduction reaction (URR) and water oxidation reaction (WOR) synergistically. The results showed that O v -ZAF was able to reduce 498.3 mg/g of U(VI) in 100 ppm uranium solution for 200 min, with a reduction efficiency of 99.8 %. O v -ZAF showed excellent reduction ability in a variety of uranium-containing waste solutions as well as in real seawater. In addition, O v -ZAF is capable of generating reactive oxygen radials (ROS) and has excellent antimicrobial activity against Escherichia coli, Staphylococcus aureus and Pseudoalteromonas xiamen. Oxygen vacancies and tandem components can tune both occupied and unoccupied orbitals near the Fermi level of O v -ZAF. This work provides a possibility of efficient uranium reduction engineering through tunable compositions and electronic structures. [ABSTRACT FROM AUTHOR]

• The high-pressure crystal structures of Sr(B,C) x (x = 7,8) systems are explored. • SrB 5 C 2 , SrB 6 C and SrB 5 C 3 exhibit significant mechanical strength. • SrB 5 C 2 is a superconductor with t c of 10.5 K at ambient pressure. Boron-carbon-based compounds have attracted considerable attention due to their exceptional properties and increasing applications in industry. In this study, we conducted a systematic structural prediction of the SrB x C 7- x and SrB x C 8- x systems under ambient and high pressures up to 20 GPa using an unbiased global structure search. Through the calculations of formation enthalpy and phonon dispersion curves, we identified three new compounds, namely SrB 5 C 2 , SrB 6 C and SrB 5 C 3 , as thermodynamically and dynamically stable under ambient pressure and high pressures up to 20 GPa. Calculations of mechanical properties reveal that these three compounds have significant mechanical strength, with estimated theoretical Vickers hardness values ranging from 23.2 to 39.8 GPa. Electronic structure calculations suggest that both SrB 5 C 2 and SrB 5 C 3 are hole conductors, with the bands crossing the Fermi level, and SrB 6 C is a semiconductor with an indirect bandgap of 2.4 eV. The electron-phonon coupling calculations using the Migdal-Eliashberg theory indicate that SrB 5 C 2 exhibits superconductivity at 10.5 K under ambient pressure, while SrB 5 C 3 shows superconductivity at a much lower temperature of 0.4 K. This finding adds to our knowledge of boron-carbide materials and provides valuable insights for the development of similar materials with good mechanical properties. [ABSTRACT FROM AUTHOR]