Interfacial Electronic Structure Research Articles

Real-Time Ultraviolet Monitoring System with Low-Temperature Solution-Processed High-Transparent p-n Junction Photodiode with a Fast Responsive and High Rectification Ratio.

We introduce an enhanced performance organic-inorganic hybrid p-n junction photodiode, utilizing poly[bis(4-phenyl) (2,4,6-trimethylphenyl)amine] (PTAA) and ZnO, fabricated through a solution-based process at a low temperature under 100 °C. Improved interfacial electronic structure, characterized by shallower Gaussian standard deviation of the density-of-state distribution and a larger interface dipole, has resulted in a remarkable fold increase of ∼102 in signal-to-noise ratio for the device. This photodiode exhibits a high specific detectivity (2.32 × 1011 Jones, ) and exceptional rectification ratio (5.47 × 104 at ±1 V). The primary light response, concentrated in the optimal thickness of the PTAA layer, contributes to response over the entire UVA region and rapid response speed, with rise and fall times of 0.24 and 0.64 ms, respectively. Furthermore, this work demonstrates immense potential of our device for health monitoring applications by enabling real-time and continuous measurements of UV intensity.

Ni/Ni4N nanoparticles anchored on 3D necklace-like carbon framework as free-standing bifunctional host for practical Li-S full cells

Inhibiting the shuttle effect, accelerating sulfur redox kinetics and controlling lithium homogeneous deposition are significant to achieve the flexible lithium-sulfur (Li-S) cells with high energy density and safety. In this study, we successfully synthesized a three-dimensional (3D) free-standing necklace-like fabric consisting of heterostructured Ni/Ni4N nanoparticles confined into hollow carbon cages implanted with N-doped carbon nanofibers (Ni/Ni4N@NCC). This unique 3D necklace-like framework and interface electronic structure of Ni/Ni4N@NCC could effectively addresses the challenges associated with both sulfur cathode and lithium anode in Li-S cells. Combine with experimental tests and DFT simulations, Ni/Ni4N@NCC not only strengthened chemical anchoring and accelerated lithium polysulfides conversion, but also induced Li uniform deposition and growth due to its excellent lithiophilicity and low Li diffusion energy barrier. For the anode, the lithium foil coating with Ni/Ni4N@NCC interlayer (denoted as Li-Ni/Ni4N@NCC anode) showed exceptional long-term cycling stability over 1000 h at the high current density of 5 mA cm−2 for high areal capacity of 5 mAh cm−2. The S-Ni/Ni4N@NCC||Li-Ni/Ni4N@NCC cell with sulfur loading (6.8mg cm−2) exhibited high areal capacities of 6.11 mAh cm−2. The synergetic effect of fascinating necklace-like structure and heterogeneous interface offer instruction for the practically viable design of high-performance flexible Li-S full cells.

Synergetic regulation of interfacial electronic structure of Cu, N co-doped carbon modified TiO2 for efficient photocatalytic CO2 reduction

TiO2 was a promising candidate material for CO2 photoreduction, but its development was greatly limited due to inherent defects such as high recombination rate of photogenerated charge carriers and limited number of active sites. In this study, a method involving chelation of metal ions with amino acids followed by high-temperature pyrolysis was employed to prepare Cu, N co-doped carbon-modified TiO2 composite materials, aiming to enhance the photocatalytic CO2 reduction performance of TiO2. The introduction of Cu, N co-doped carbon effectively improved the surface morphology of TiO2, increased the specific surface area and porosity, and enhanced the adsorption capacity of CO2. Simultaneously, the modification of TiO2 by Cu, N co-doped carbon optimized the electronic structure of catalysts, facilitating the separation and transfer of photogenerated electron-hole pairs, reducing charge carrier recombination, and thereby synergistically improving the thermodynamics and kinetics of CO2 reduction. Photocatalytic performance tests revealed that 10 % Cu-TiO2 exhibited the best CO2 reduction performance at a calcination temperature of 450 °C, with a CO production rate of up to 46 μmol·g−1·h−1, approximately 18 times that of pure TiO2. Density functional theory (DFT) calculations further confirmed that the introduction of Cu, N co-doped carbon reduced the Gibbs free energy of the CO2 reduction reaction, promoting the reaction. This study provides a simple, cost-effective strategy for developing efficient photocatalytic CO2 reduction materials.

Enhanced water‐splitting performance: Interface‐engineered tri‐metal phosphides with carbon dots modification

AbstractDesigning integrated overall water‐splitting catalysts that maintain high efficiency and stability under various conditions is an important trend for future development, yet it remains a significant challenge. Herein, novel nanoflower‐like tri‐metallic Ni–Ru–Mo phosphide catalyst ((Ni–Ru–Mo)P@F‐CDs), integrated with F‐doped carbon dots (F‐CDs), were synthesized via a straightforward hydrothermal process and subsequent phosphatization. Attributable to precise interface engineering and electronic structure optimization, (Ni–Ru–Mo)P@F‐CDs exhibit exceptional bi‐functional catalytic activity in alkaline conditions, achieving remarkably low overpotentials of 231 and 123 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively, at a current density of 100 mA cm−2. Industrially, only 1.426 V is needed for the same efficacy. Additionally, the catalyst requires merely 1.508 and 1.564 V for overall water splitting in 1 M KOH and simulated seawater, respectively, at 100 mA cm−2. The catalyst also shows excellent stability, with minimal performance decline over 100 h within 100–200 mA cm−2. Density functional theory calculations indicate that the interface structure synergistically optimizes Gibbs free energy for H* and O* intermediates during HER and OER, respectively, accelerating electrochemical water‐splitting kinetics.

Investigation of the effect of partial Co substitution by Ni and Fe on the interface bond strength of WC cemented carbide based on first-principles calculations

In this work, the effect of Ni and Fe replacing part of Co on the interfacial properties of WC cemented carbides was evaluated by using first-principles calculations and WC/Co and WC/CoNiFe cemented carbides were prepared by powder metallurgy. The effects of replacing part of the Co by Ni and Fe on the interfacial electronic structure, interfacial bond strength, microstructure and mechanical properties of WC cemented carbides was investigated by establishing the WC/Co and WC/CoNiFe interfacial models and examining the porosity, KPFM and microhardness of the actual samples. The results indicate that the substitution of partial Co by Fe and Co has little effect on the interface binding energy and interface structure of WC cemented carbides. Co, Ni, and Fe atoms can all form strong covalent and metallic bonds with W atoms, with atomic bonding strength W-Fe>W-Co>W-Ni. Fe atoms play a major role in the strength of the WC/CoNiFe interface. The porosity of the WC/CoNiFe cemented carbide sample is 0.78 %, which is significantly smaller than that of the WC/Co cemented carbide and the porosity distribution is relatively homogeneous. The hardness of WC/CoNiFe cemented carbide is lower (1182 HV) than that of the WC/Co cemented carbide (1320 HV) but the distribution is much more uniform than that of the WC/Co cemented carbide.

High-current-density PB@S-NiCo nanorod array catalyst for urea-assisted water splitting

To alleviate severe environmental and energy pressures, urea oxidation reaction (UOR) was frequently studied as an alternative electrochemical hydrogen production anode reaction for its low theoretical voltage. Herein, a series of self-supported UOR catalysts were synthesized on the combination of PB nanoparticles and sulfur doped NiCoCO3(OH)2 nanorod arrays (PB@S-NiCo NRA) on copper foam. By changing the modifying time of S-NiCo NRA precursor in K3[Fe(CN)6] solution, PB@S-NiCo-X (X=10, 60, 120 for reaction time) were obtained. The highly hydrophilic heterostructure array can adjust the interface electronic structure and accelerate the mass transfer process, thereby optimizing the thermal/kinetic dynamics of urea electrolysis hydrogen production. Over the typical PB@S-NiCo-60 catalyst, only 1.48 V (UOR) and 1.83 V (overall urea electrolysis) were required to drive a large current density of 500 mA cm−2, showing excellent electrocatalytic activities of the composite catalysts. Furthermore, PB component in the composite catalyst enhanced the reaction kinetics to achieve good stability at high current densities. This study provides new ideas for durable urea electrolysis-assisted H2 production.

Coupling of modulating d-band center and optimizing interface electronic structure via MXene and Bi-metal doping in CoP achieving efficient bifunctional catalytic activity for water splitting

Bifunctional electrocatalysts that exhibit excellent catalytic activity for both hydrogen (HER) and oxygen evolution reactions (OER) are ideal for alkaline overall water splitting. The unique structure and diverse composition of cobalt phosphide catalysts are highly favorable for enhancing catalytic reaction kinetics. However, cobalt phosphide electrocatalysts typically exhibit insufficient OER activity. To overcome this text, we synthesized a Ru and V co-doped CoP-coupled highly conductive MXene catalyst with nano-arrays by in-situ growth on the surface of carbon cloth. The HER and OER overpotentials of the catalyst at 10 mA cm−2 current density were 30 and 206 mV, respectively. Furthermore, a series of physicochemical characterizations and first-principles calculations demonstrated that the increased HER and OER activities resulted from the synergistic effect established by the double doping and heterostructure. This effect produced an effective modulation of the d-band center of the catalysts, promoting adsorption effects on the intermediates. In conclusion, this work presents a novel approach to improving the electrocatalytic activity of phosphides and provides a faster and more environmentally friendly method for separating hydrogen from water.

Designing multi-functional MoS2/rGO piezocatalysts based on bacteria-catalyst topological interactions and electron pump effects for efficient water disinfection

In catalytic technology, the capability of nanocatalysts to generate reactive species (ROS) and the rapid contact between ROS and target pollutants are critical for the catalytic reaction. Herein, we proposed an effective strategy to construct multi-functional MoS2/rGO piezocatalysts based on bacteria-catalyst topological interactions and electron pump effects, which possessed high carrier separation ability and adhesion to bacteria, ensuring the effective utilization of ROS. Attributed to the unique 3D heterogeneous structure and interface electronic structure, MoS2/rGO could completely inactivate 6.21 log10 cfu mL−1 of E. coli K-12 within 30 min under ultrasonic conditions, significantly faster than pure MoS2. It was demonstrated experimentally and theoretically that the introduction of rGO led to the generation of a large amount of ROS by enhancing the piezoelectric properties and conductivity of MoS2/rGO, while the topological interactions between MoS2/rGO and bacteria facilitated effective bacteria capture, improving the utilization of ROS. Additionally, Kelvin Probe Force Microscopy texting confirmed that rGO acts as an electron pump, effectively attracting electrons from bacterial cells, which disrupted bacterial metabolic processes, increased oxidative stress, and further enhanced the bactericidal effect. The mechanisms of topological interactions and electron pump effects elucidated in this work offer new insights into the design and understanding of efficient bactericidal materials in water purification applications.

Interfacial electronic structure modulations of Au@CuS with defective Ni-doped CoS2 facilitates the electroreduction of N2 into NH3

The nitrogen reduction reaction (NRR) offers a sustainable pathway for ammonia production. However, its effectiveness is hindered by the selective adsorption of nitrogen and the subsequent occurrence of the hydrogen evolution reaction. In this work, a novel and efficient NRR catalyst, Au@CuS heterostructured nanoparticles supported on carbon-coated Ni-doped CoS2 hollow nanocages (Au@CuS/Ni-CoS2/C), was designed and synthesized to enhance the conversion of N2 to NH3 under ambient conditions. The defective Ni-CoS2@C nanocages not only provide a larger surface area for the loading of Au@CuS nanoparticles but also improve conductivity and promote synergistic effects among different components within catalyst. Both experimental investigations and density functional theory (DFT) calculations reveal that the integration of Au and CuS leads to unique inorganic donor–acceptor couplings with electron enriched in Au nanoparticles due to the higher work function of Au compared to CuS. This electron enrichment expedites the adsorption and dissociation of N2 molecules over the electron-rich Au active sites, thereby significantly optimizing the adsorption of intermediates and catalyzing subsequent hydrogenation reduction processes. Benefiting from these synergistic advantages, the resulting Au@CuS/Ni-CoS2/C catalyst exhibited high NRR electrocatalytic activity with a maximum NH3 yield of 25.61 µg h−1 mg−1cat. and a Faraday efficiency of 14.99 % at –0.3 V (vs. reversible hydrogen electrode, RHE), surpassing those of Au@CuS, Ni-CoS2/C, and Au/Ni-CoS2/C. This work presents a new strategy for precisely adjusting the valence state of Au species, thereby facilitating the production of valuable ammonia through NRR.

Strong Interactions between Au Nanoparticles and BiVO4 Photoanode Boosts Hole Extraction for Photoelectrochemical Water Splitting.

Strong metal-support interaction (SMSI) is widely proposed as a key factor in tuning catalytic performances. Herein, the classical SMSI between Au nanoparticles (NPs) and BiVO4 (BVO) supports (Au/BVO-SMSI) is discovered and used innovatively for photoelectrochemical (PEC) water splitting. Owing to the SMSI, the electrons transfer from V4+ to Au NPs, leading to the formation of electron-rich Au species (Auδ-) and strong electronic interaction (i.e., Auδ--Ov-V4+), which readily contributes to extract photogenerated holes and promote charge separation. Benefitted from the SMSI effect, the as-prepared Au/BVO-SMSI photoanode exhibits a superior photocurrent density of 6.25 mA cm-2 at 1.23 V versus the reversible hydrogen electrode after the deposition of FeOOH/NiOOH cocatalysts. This work provides a pioneering view for extending SMSI effect to bimetal oxide supports for PEC water splitting, and guides the interfacial electronic and geometric structure modulation of photoanodes consisting of metal NPs and reducible oxides for improved solar energy conversion efficiency.

Strong Interactions between Au Nanoparticles and BiVO4 Photoanode Boosts Hole Extraction for Photoelectrochemical Water Splitting

AbstractStrong metal‐support interaction (SMSI) is widely proposed as a key factor in tuning catalytic performances. Herein, the classical SMSI between Au nanoparticles (NPs) and BiVO4 (BVO) supports (Au/BVO‐SMSI) is discovered and used innovatively for photoelectrochemical (PEC) water splitting. Owing to the SMSI, the electrons transfer from V4+ to Au NPs, leading to the formation of electron‐rich Au species (Auδ−) and strong electronic interaction (i.e., Auδ−‐Ov‐V4+), which readily contributes to extract photogenerated holes and promote charge separation. Benefitted from the SMSI effect, the as‐prepared Au/BVO‐SMSI photoanode exhibits a superior photocurrent density of 6.25 mA cm−2 at 1.23 V versus the reversible hydrogen electrode after the deposition of FeOOH/NiOOH cocatalysts. This work provides a pioneering view for extending SMSI effect to bimetal oxide supports for PEC water splitting, and guides the interfacial electronic and geometric structure modulation of photoanodes consisting of metal NPs and reducible oxides for improved solar energy conversion efficiency.

Mechanical behavior of Ni/Ti bilayer-based shape memory alloys: Endorsement via atomistic simulations

To gain a structural and thermodynamic understanding along with the interpretation of atomic diffusion in a Ni/Ti bilayer, detailed first-principles simulations using density functional theory (DFT) and molecular dynamics (MD) simulations have been carried out. The interface energies and electronic structure of the Ni/Ti bilayer have been calculated using DFT. The MD simulations of interface atomic diffusion in the Ni/Ti bilayer were performed at 773 K for different annealing times to investigate the formation of Ni–Ti alloy. The simulated results indicate that Ni atoms predominantly diffuse into the Ti side. The radial distribution functions (RDFs) have been plotted to understand the nature of bonding that exists between the Ni and Ti atoms in the bilayer. The shape of the RDFs reveals information about the extent to which Ni and Ti atoms mix together. Classical MD simulations have been used to simulate the deformation behavior of the material under tension and to investigate the effects of annealing time on the mechanical properties of the materials.

Effect of multi-interface electron transportation and molecule adsorption on hydrogen evolution reaction

The widespread industrial application of water electrolysis to hydrogen production is limited by its high cost, high energy consumption and low conversion efficiency. This work demonstrates the energy-efficient hydrogen production can be attained by the rational design of electrolyser with efficient electrocatalyst. Typically, the efficient CoP3-FeOOH-Ni2P-C3N4 (CoFeNiC) electrocatalyst is prepared by calcining the mixture of both ZIF-67 and NiFe-LDH, which exhibits a good electrolysis performance in an alkaline electrolyte. At 10 mA cm−2, the oxygen evolution reaction (OER) overpotential of CoFeNiC (146 mV) is lower than the previously reported results, and the Faraday efficiency (FE) reaches 94.8 %. In addition, density functional theory (DFT) calculations demonstrate that the large work function difference between FeOOH, Ni2P and C3N4 is beneficial to form stable hetero-interface, which significantly optimize the interface electronic structure and enhances the electron transfer from FeOOH, Ni2P to C3N4; and CoP3 has a strong molecule adsorption ability. Thereby CoFeNiC shows an enhaned water-splitting efficiency. Moreover, an asymmetric electrolyzer is constructed by using CoFeNiC as cathode and NiFe-LDH as anode. At 150 mA cm−2, the cell voltage of CoFeNiC//NiFe-LDH electrolyzer decreases by 11.67 %, compared with symmetric NiFe-LDH electrolyzer. The i-t test shows that the asymmetrical electrolyzer exhibits a good stability at a high current density.

Tuning the Interfacial Electronic Structure of MoS2 by Adsorption of Cobalt Phthalocyanine Derivatives

Tuning the Interfacial Electronic Structure of MoS₂ by Adsorption of Cobalt Phthalocyanine Derivatives

Interface energy, adhesion work and electronic structure of Ti3AlC2/Ag interface calculated from first principles

In this paper, based on the first-principles calculation of density functional theory, the adhesion work, interface energy and electronic structure of Ag/Ti3AlC2 interface are systematically studied. In the calculation process, 18 interface models with different terminals and different stacking sequences are considered. After comparing the calculation results, it is found that the interface model of Al terminal is the most stable among the six interface models of Ti1(C), Al, C(Ti2), Ti2(Al), C(Ti1) and Ti2(C). After changing the stacking order of Al terminal interface atoms, it can be found that the order of interface stability of Al terminal is HCP > FCC > OT according to the interface energy, and the interface energy of HCP interface model is 2.209J/m2. After the comprehensive analysis of adhesion work, interface energy and electronic structure, it is found that the theoretical calculation results are consistent with the previous experimental results. Al atoms have a tendency to move to the Ag matrix and form Ag (Al) solid solution, and the formation of solid solution further increases the stability of the interface.

NiO surface reduction by Nd overlayers

Metal/metal oxide interfaces have significant impact on modern technologies like microelectronics, solar cells, magnetic storage, and sensors due to their distinct electronic and structural properties. Such interfaces sometimes deviate from ideal bulk-termination which influences the system's overall performance. Here, we present the study of the interfacial electronic structure formed by the deposition of Nd layers onto NiO thin films utilizing X-ray photoelectron spectroscopy (XPS) and Ultraviolet photoemission spectroscopy (UPS). Our study indicates that the interface between the rare earth metal (Nd) and NiO differs from the ideal sharp interface. The portion of NiO surface reduced to metallic Ni while the deposited Nd metal is oxidized, indicating the interfacial oxidation/reduction process. The thickness of this interfacial Ni layer increases with increase in Nd metal deposited and reaches maximum depth of 3.0 Å when effective Nd overlayer thickness reaches 7.9 Å. Such an interface reaction could be utilized in heterostructures where an intentional reduction of the oxides is desired.

An effective descriptor for identifying the electrocatalytic activity and selectivity of bilayer carbon-based heterojunction catalysts

The usage of composite carbon-based materials supported by graphene has emerged as a powerful selection for designing electrocatalytic electrodes due to their agile electronic transmission and diversiform redox active sites. Here, we constructed fresh electroactive organic catalysts for hydrogen carrier synthesis by stacking a series of organic molecules on transition metal azide doped graphene substrates, in anticipation of these bilayer heterostructures to breathe new life into electrocatalysis. As expected, several promising cathodic catalysts were speculated through first principles calculations, such as Co-PMDT for H2 generation and Co-PQ for ammonia (NH3) synthesis. However, facing such an intricate interface engineering and electronic structure regulation undoubtedly poses a challenge to the time-consuming computational screening work. To tackle this, an effective descriptor was proposed as a predictive tool for identifying the activity and selectivity toward diverse chemical reactions, which allows us to systematically fine-tune the catalysts' properties in order to enhance their electrocatalytic performance. Our work may offer feasible approaches for the rational design of advanced electrocatalysts.

Insight into the Grain Refining Mechanism of Al–Ti–C and the Interfacial Properties between the Inoculants and Aluminum

The grain refinement mechanism of Al–Ti–C grain refiners used in the casting procedure of aluminum has been studied by first‐principles calculation. Considering the controversy over Al3Ti, TiC, or Al3Ti–TiC as nucleation sites, the adsorption behavior of possible nucleation surfaces for Al atoms, including adsorption energies and adsorption sites, as well as the interfacial properties of Al/Al3Ti/TiC are calculated and compared. In the results, it is shown that the Al3Ti(112) surface has a stronger adsorption capacity for Al than TiC. By using the edge‐to‐edge matching crystallographic model and the calculation of the adsorption energy, it is found that the monolayer Al3Ti(112) can be stabilized on the TiC(100) surface, and the combination of TiC and monolayer Al3Ti can significantly improve the adsorption capacity of Al. Interfacial electronic structure analysis shows stronger chemical bonding between Al and Ti at the Al/Al3Ti/TiC interface compared to Al/Al3Ti, which explains that the monolayer Al3Ti covering the TiC surface has the strongest adsorption capacity for Al atoms. Therefore, it is speculated that TiC with a monolayer of Al3Ti covering the surface will serve as a potential nucleation site during grain refinement, which will provide a theoretical reference for future research work.

In-situ topotactic synthesis of decahedron BiVO4/2D networks Bi2S3 heterojunctions for efficient Cr(VI) reduction: Improved charge separation and imaged at the single-particle level

Epitaxial heterostructure has an optimized interfacial electronic structure compared to the traditional random heterostructures. However, accurately monitoring the interfacial charge transfer dynamics remains a grand challenge. We report here that single-particle spectroscopy techniques address this challenge by performing photoluminescence (PL) lifetime imaging and spectral fitting of interfacial micro/nano regions. A novel facet-selective BiVO4/2D nano-network Bi2S3 heterostructure is synthesized by a simple hydrothermal method. Single-particle PL spectroscopy shows that the PL emission at the oriented epitaxial heterojunction interface in BVO/S-O is weakened, and the PL lifetime increases by 213 % and 105 % compared to a single BiVO4 and random heterojunction particles, respectively, indicating that the topological heterojunction interface effectively promotes the separation of charge carriers. In addition, the possible mechanism of photocatalysis was also discussed in detail. Our work reveals the advantages of unique spatial structures and topological epitaxial interfaces in charge separation, which has great prospects for photocatalytic applications.

Generalized Substrate Screening GW for Covalently Bonded Interfaces.

An accurate description of the interfacial quasiparticle electronic structure is key to the design of heterogeneous materials. While the first-principles GW approach is state-of-the-art, the computational cost is high for large interface systems. This has led to the substrate screening GW approach for weakly coupled interfaces, which breaks down for covalently bonded interfaces. In this work, we present the generalized substrate screening GW approach, based on the following two considerations: (i) the contribution of the interfacial covalent bond to the polarizability can be efficiently calculated with a low energy cutoff; (ii) the contribution of the deprotonated adsorbate to the interface polarizability can be well approximated by that of the protonated molecule. Our approach is exemplified using interfaces formed between benzene-1,4-dithiol (BDT) and Au(111), which feature the widely used Au-S bonds in experiments. Our work provides a robust and simple scheme for accurate and efficient GW calculations of covalently bonded interfaces.