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The electrocatalytic reduction of CO 2 (CO 2 RR) into value-added hydrocarbons is limited due to high limiting potential (U L) and competing hydrogen evolution reaction (HER). To find the best catalyst for CO 2 reduction the concept of hydrogen poisoning was not considered in the catalyst screening process. Herein, we present a simple screening method and graphical construction using multiparameter optimization for the design of highly active and selective single-atom catalysts (SAC) using density functional theory calculations. A series of SAC namely, MN4, MBN3 and H@MBN3 (M: metal) are investigated for CO 2 RR. Our results revealed that MN4 and MBN3 SAC are not favorable for CO 2 RR due to high U L > −0.85 V and hydrogen poisoning (ΔG H* < 0), respectively. H@MBN3 SAC (stable compounds forming H–B bonds) are identified as efficient catalysts with a low value of U L and significantly hinder the competitive HER. Among these, H@CoBN3 and H@FeBN3 SAC show excellent CO 2 RR activity with limiting potential −0.30 and −0.44 V respectively for CH 4 production and no chance of HER. Scaling relations reveal the importance of *COOH/*CHO binding energy (E b) as an energy descriptor to evaluate the catalytic performance. This work provides a new theoretical perspective to design a highly selective catalyst for CO 2 RR. [Display omitted] • Simple graphical construction is provided to screen the catalyst for selective CO 2 RR. • The hydrogen poisoning issue is addressed, which blocks the active site. • Hydrogen assisted catalysts (H@MBN3) are designed for highly efficient CO 2 RR. • The binding energy of *COOH is defined as an energy descriptor for SAC catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Heteroatoms (B, N) doping to switch the CO oxidation mechanism from ER to LH. • A screening criterion is defined to get an efficient catalyst for CO oxidation. • 3B edge doped AGNR is identify as an active catalyst following LH mechanism. • Sabatier activity and TOF values of 0.90 and 2.47, respectively. In heterogeneous catalysis, the LH (Langmuir Hinshelwood) mechanism is more efficient and recommended over any other mechanism adopted for CO oxidation. However, the LH mechanism over a carbon surface is a challenge and is paused to be applied to any carbon surface in practical application. In this work, we carried out density functional theory to study how the incorporation of nitrogen, boron atom (C→N, C→B) and co-doping on graphene nanoribbons can modify the catalytic activity of the surface and the preference between ER (Eley-Ridel) and LH mechanism is explored. Boron plays a crucial role in the adsorption of both CO and O 2 , whereas nitrogen doping can only activate O 2 molecule through altering the triplet ground state. Considering the activation energy for the first CO 2 formation and CO binding strength, we have defined a window to identify the operation of the LH mechanism in the catalysis. 3B edge doped AGNR (armchair graphene nanoribbon doped with three boron atoms at its edge) is identified as an active catalyst for the CO oxidation through the LH mechanism, with the SA (Sabatier activity) and TOF (turnover frequency) values of 0.90 and 2.47, respectively. This approach will help to search for metal-free catalysts for the CO oxidation with the efficient LH mechanism. [ABSTRACT FROM AUTHOR]

The composition of two different categories of anode materials, i.e. layered and alloy type is the future of anode material in Li-ion batteries. In our work, using First-principles approach, we proposed multilayer heterostructure of graphene/graphite (layered type) with silicon monolayer (Si-ML) (origin is alloy type), as a potential anode material for LiB's. The synergetic effect of the delocalized π electron of carbon and localized π electron of Si-ML plays a crucial role in maintaining the electron and ion conductivity increases the stability and specific capacity with moderate open circuit voltage. The model structures proposed in this work shows high specific capacities in the range of 748 to 438 mAh-gm−1. This indicates that we can tune the specific capacity using the different ratio of carbon and silicon layers. The localized π electron helps to restrict the volume expansion within 15% for a fully lithiated model structure. The low interlayer diffusion energy of Li-ion makes all the heterostructure as a potential anode material. The proposed study will help to understand the Li storage properties of the carbon/silicon based composite to develop the anode materials with a certain approach. Image 1 • Localized π electron of Si-ML helps to increase the stability and specific capacity. • Lower the concentration of Si would be better for lowering the value of average OCV. • Specific capacities in the range of 748 to 438 mAh-gm−1. • Low interlayer diffusion energy of Li-ion. [ABSTRACT FROM AUTHOR]

Presence of curvature is considered as a tuning parameter to activate the hydrogen storage capability of carbon nanostructures. Here, we explicate the role of 'intra-curvature' in a set of single-walled carbon nanohorns (SWCNHs), to adsorb light metal ad-atoms (M) e.g. Li, Na, Ca and subsequently explore the metal-doped systems for hydrogen storage application using density functional theory. The binding strength of ad-atoms on SWCNHs of different curvature is correlated with the π electron occupancy of the corresponding carbon ring. Higher π electron occupancy causes significantly high binding energy of the metal ad-atoms (M), thereby indicating high stability of those M−C bonds for intra-curvature values more than 11⁰, even at a higher temperature. After full hydrogenation, Li-doped SWCNHs are found to contain a maximum of 7.5 wt % of hydrogen. Overall, our results indicate that Li-doped SWCNHs with intra-curvature values higher than 11⁰, is a potential candidate for hydrogen storage. Image 1 • Exploring metal-doped single-walled carbon nanohorns for hydrogen storage. • Intra-curvature of nanohorns is exploited to tune the metal-carbon bond strength. • π electron occupancy of the hexagonal rings acts as the main descriptor. • Higher stability of metal-carbon bonds for intra-curvature values more than 11°. • Li-doping with intra-curvature more than 11° is suitable for hydrogen storage. [ABSTRACT FROM AUTHOR]

One of the promising approaches to synthesize ammonia in ambient conditions is through artificial photocatalytic nitrogen fixation. In order to overcome the hassles of charge carrier recombination and finite light response of photocatalysts, high charge separation efficiency and a wide window for optical absorption are imperative. Herein, Ni-incorporated ZrO 2 /Bi 2 O 3 has been fabricated with p-n heterojunction and a bandgap aligned to absorb visible light up to 560 nm which play an important role in enhancing the production rate of ammonia. The catalyst exhibits a maximum ammonia generation rate of 9668.2 µmol h−1 g−1. Further, systematic characterization studies confirm the formation of the desired photocatalyst. This work presents a propitious strategy to configure appropriate visible light responsive photocatalyst that efficiently reduces nitrogen. [Display omitted] • Ni-incorporated ZrO 2 /Bi 2 O 3 fabricated via ultrasound-assisted hydrothermal method. • p-n heterojunction for effective charge carrier separation. • Adsorption and activation of N 2 molecule using oxygen vacant sites. • 8-fold increase in ammonia production with 5% TEOA in comparison to ZrO 2 /Bi 2 O 3. [ABSTRACT FROM AUTHOR]

The development of two-dimensional (2D) material or heterostructure as an anode material is necessary to enhance the electrochemical performance of Li-ion batteries (LIBs) but finding the correct combination is a challenge. In the present work, using First principles study, we have proposed borophosphene (BP-ML) and graphene-based multilayer heterostructure as a possible anode material. We have found that BP-ML and graphene-based heterostructure are conductive in nature. Here, we have also investigated the role of P z (π) and P y (σ) atomic orbital bands of BP-ML and graphene. On Li intercalation, charge transfer is mainly site and interface definitely which helps to improve the specific capacity. The specific capacity of the proposed heterostructure varies from 546 to 427 mA h/g. For maximum Li confirmation, the volume expansion of these heterostructures is about 14–16%. The presence of graphene helps to maintain the open-circuit voltage (OCV) of heterostructure on an average 0.7 V. Also, helps to support the diffusion barrier energy in the range of 0.27–0.71 eV. This proposed 2D heterostructure could be the future material for the LIB's anode material. [Display omitted] • BP-ML/Gr-ML heterostructure as prospective anode material for LiBs. • Specific capacities in the range of 543 to 427 mA h-gm−1. • Higher charge transfer from Li to B and P atoms of BP-ML. • Open circuit Voltage (OCV) of about 0.7 V for BP-ML/Gr-ML heterostructure. • Minimal structure distortion during Li intercalation/deintercalation process. [ABSTRACT FROM AUTHOR]

Here we report, structural and electrical transport properties of reduced graphene oxide as a function of oxygen bonding configuration. We find that mainly epoxy (C O C) and carbonyl (C O) functional groups remain as major residual components after reduction using three different reducing agents. We calculate the band structure in the presence of epoxy and carbonyl groups and defects. Finally, we calculate the theoretical band mobility and find that it is less for the carbonyl with epoxy system. We correlate the distortion of linear dispersion and opening of bandgap at K-point with conductance for different graphene system in presence of oxygen moieties. [ABSTRACT FROM AUTHOR]

Dioxygen adsorption and activation on metal-ligand systems are the key elements for biological oxidative metabolisms and also catalyst design for the oxygen reduction reaction (ORR). We show, through first-principles calculations, that similar dioxygen adducts can form on metal-free n -type doped hexagonal boron nitride ( h-BN ) nanostructures. The density of electron donors determines the charge state of dioxygen, either in superoxo and peroxo, which exactly correlates with the ‘end-on’ and ‘side-on’ configurations, respectively. Activated O 2 in the superoxo state shows a better catalytic performance possibly mediating the direct four-electron reduction. The formation of hydrogen peroxide (H 2 O 2 ) is practically eliminated, and thus we suggest that a surface coated with the n -type doped h-BN can be the basis for an ORR catalyst with increased stability. [ABSTRACT FROM AUTHOR]

In the architecture described, cuprous oxide (Cu2O) is tamed to be highly (111) plane oriented nanostructure through adjusting the deposition postulate by glancing angle deposition technique. In the controlled atmosphere oxygen vacancy is introduced into the Cu2O crystal subsequently fostering an impurity energy state ( Eim) close to the conduction band. Our model of Cu2O electronic structure using density functional theory suggests that oxygen vacancies enhance the electron donating ability because of unshared d-electrons of Cu atoms (nearest to the vacancy site), allowing to pin the work function energy level around 0.28 eV compared to the bulk. This result is also complemented by Kelvin probe force microscopy analysis and X-ray photoelectron spectroscopy method. Oxygen vacancy in Cu2O (Cu2O1- δ) exhibits promising field emission properties with interesting field electron tunneling behavior at different applied fields. The films show very low turn-on and threshold voltages of value 0.8 and 2.4 V μm−1 respectively which is influenced by the oxygen vacancy. Here, a correlation between the work function modulation due to the oxygen vacancy and enhancement of field emission of Cu2O1- δ nanostructure is demonstrated. This work reveals a promising new vision for Cu2O as a low power field emitter device. [ABSTRACT FROM AUTHOR]

Using first principles method we elaborately discuss the magnetic, elastic and optical properties of pure, Zn and O vacant ZnO 2 . It is found that the electronic structure and band gap of ZnO 2 is not sensitive to the active on-site Coulomb interaction term U d , but found to be depending on the term U p . The role of orbitals subject to the correlation is thus completely opposite for the case of ZnO 2 in respect of ZnO. Interestingly, the Zn vacancy converts ZnO 2 as “ d 0 magnet”. Indeed, our analysis show that, Zn vacancy transmuted O 2 2− state into O 2 δ +2− state, indicating the partially filled π ∗ states are the governing reason for the d 0 magnetism. Both HSE06 and PBE0 functional confirm the same. The similar phenomena has been observed for other peroxide materials XO 2 (X = Mg, Ca, Sr, Ba) studied here. Our results suggest that this class of materials can be studied further to exploit its potential in spintronic devices. Further the elastic properties have been estimated for pure ZnO 2 at different pressures and for Zn and O vacant ZnO 2 to know the stability of the system. Zn vacancy in ZnO 2 also tunes optical properties, indicating its potential application in other areas. [ABSTRACT FROM AUTHOR]

Single and multiple As adatom adsorptions on double vacancy (DV) defect graphene sheets are extensively analyzed using dispersive force corrected density functional theory (DFT). Defect pentagonal and heptagonal bridge sites and the immediate neighborhood of the defect center are found to be most favorable for this purpose. Quantitative analysis of electronic structures revealed the As-C bonding to be mostly ionic in nature with some covalency arising from the overlap of As p states and C p states. For multiple As adatoms adsorption in close vicinity, ionicity of the As-C bonds are found to decrease to support As-As cohesion; the net result of which is manifested as better binding of dioxygen molecule with them and additional weakening of the O-O bond in the adsorbed state. Free energy profile of oxygen reduction reaction (ORR) cycle using multiple As atom adsorbed DV graphene as electrocatalyst predicts high affinity towards four electron process and forbids the formation of H2O2via two electron process. Other traits, such as no intermediate O-O-H formation and high stability of the catalytic system throughout the reaction process indicate As adatoms adsorbed on DV graphene system to be efficient and highly stable as an alternate Pt free ORR electrocatalyst. [ABSTRACT FROM AUTHOR]

Highlights: [•] IR and Raman analysis could be used to investigate the type of conformer. [•] Shrinkage of lattice parameter, results in blue shift of Raman frequency. [•] Formation of shallow donor level due to hydrogenation. [•] Chair conformer properties are largely differ from Boat and Stirrup conformer. [ABSTRACT FROM AUTHOR]

[Display omitted] • We give a deeper reasoning relating vacancy, electronic structure and stability. • Vacancy increases σ and decreases π occupancies of the neighbouring boron atoms contributing to stability. • Carbon doping reduces the σ electrons of the adjacent boron atoms making them less reactive towards O* intermediate. • Dual carbon doping makes β12 borophene more efficient towards oxygen evolution reaction. In borophene, vacancy is a major reason for stability. However, a detailed understanding relating to vacancy and electronic property remains unexplored. Using Density Functional Theory (DFT) the effect of vacancy and doping on stability, electronic and catalytic properties of borophene is addressed in this work. It is shown how vacancy increases σ-electrons and decreases π-electrons of the neighboring boron atoms with the magnitude decreasing from 4 to 6-coordinated atoms, thereby contributing to their stability. The role of single and dual carbon doping on σ- and π-occupancy is explored. In addition, we have shown that dual carbon doping on β 12 -borophene analogue reduces the overpotential for oxygen evolution reaction (OER). We observed that the charge deficient boron atom helps in the reduction of oxygen binding and can decrease the overpotential towards OER. Overall, this work would help in fundamental understanding towards borophene stability and aid in choosing the suitable dopant for catalytic applications considering the stability. [ABSTRACT FROM AUTHOR]

Carbon based electrocatalysts are well known promising candidates for the oxygen reduction reaction (ORR), but the random approach to find the best catalyst using experimental method delayed the screening process and it leads to a huge cost with less proficiency. Using Quantum Mechanics followed by Machine Learning (QM/ML) approach, we can predict the best catalyst faster way and the origin of the cause can be identified for further development of carbon-based catalyst. Using the π electronic descriptor unveiled using density functional theory, we applied the analytical simple fit method and six different machine learning algorithms to develop a highly effective predictive model to estimate ΔG OH. Furthermore, structural relations of ZGNR and AGNR are demonstrated to estimate the D π (E F), R-O π , and ΔG OH of different widths of ribbon that reduces additional DFT calculations. By applying both SVR predictive model and structural relations, we predicted the ORR performance of 2500 sites of GNRs and listed a few most ideal active carbon sites with lower overpotential (η < 0.5V). To validate our study, we predicted the ORR performance of different sites in 0D, 1D, 2D doped graphene systems using SVR model and confirmed the values with the DFT computed results. [Display omitted] • We proposed a QM/ML based predictive model to estimate site-specific ORR activity. • π orbital descriptors are used as features in machine learning methods. • SVR predictive model is developed to find accurate ORR activity of graphene system. • Structural correlation between descriptors and width of nanoribbon is identified. [ABSTRACT FROM AUTHOR]

Highlights: O-functionalization at the edges of boron carbonitride induces charge polarization effect on B. 0.1 M HCl serves to preserve the catalyst active site from poisoning effect by electrolyte anions. Experimental and theoretical findings go hand-in-hand towards high yield of ammonia. Ammonia has been recognized as the future renewable energy fuel because of its wide-ranging applications in H2 storage and transportation sector. In order to avoid the environmentally hazardous Haber–Bosch process, recently, the third-generation ambient ammonia synthesis has drawn phenomenal attention and thus tremendous efforts are devoted to developing efficient electrocatalysts that would circumvent the bottlenecks of the electrochemical nitrogen reduction reaction (NRR) like competitive hydrogen evolution reaction, poor selectivity of N2 on catalyst surface. Herein, we report the synthesis of an oxygen-functionalized boron carbonitride matrix via a two-step pyrolysis technique. The conductive BNCO(1000) architecture, the compatibility of B-2pz orbital with the N-2pz orbital and the charging effect over B due to the C and O edge-atoms in a pentagon altogether facilitate N2 adsorption on the B edge-active sites. The optimum electrolyte acidity with 0.1 M HCl and the lowered anion crowding effect aid the protonation steps of NRR via an associative alternating pathway, which gives a sufficiently high yield of ammonia (211.5 μg h−1 mgcat−1) on the optimized BNCO(1000) catalyst with a Faradaic efficiency of 34.7% at − 0.1 V vs RHE. This work thus offers a cost-effective electrode material and provides a contemporary idea about reinforcing the charging effect over the secured active sites for NRR by selectively choosing the electrolyte anions and functionalizing the active edges of the BNCO(1000) catalyst. [ABSTRACT FROM AUTHOR]

Fine control over the graphitization level of carbonized nanostructures can play a strategic role in tuning the crystallization of supported nanocatalysts, thereby modulating the kinetics of catalysis. However, realizing the synergistic interplay of graphitization‐tunable support and supported catalysts poses a significant challenge. This study proposes a current pulse‐induced ultrafast strategy for developing MOF‐derived graphitic nano‐leaves (GNL) and supported ultrafine ruthenium nanoclusters exhibiting selective crystallization states depending on the tunable graphitization level of GNL. The resulting ultrafine (≈0.7 nm) amorphous‐ruthenium nanoclusters linked with GNL (a‐Ru@GNL500) exhibit state‐of‐the‐art performance in the hydrogen evolution reaction (HER), requiring very low overpotentials of only 23.0 and 285.0 mV to achieve current densities of 10 and 500 mA cm−2, respectively. Furthermore, a‐Ru@GNL500 demonstrates exceptional operational stability for 100 h under high HER currents of 200 and 400 mA cm−2. Density functional theory reveals that the unique electronic structure of a‐Ru and the cooperative effect of cobalt embedded in the graphitic layer lower the occupancy of the antibonding orbital, resulting in an accelerated HER process. Additionally, the unique electronic structure, highly conducting GNL, and efficient bubble release dynamics of super‐aerophobic a‐Ru@GNL500 contribute to reduced overpotentials, particularly at high HER current densities. [ABSTRACT FROM AUTHOR]

Effective integration of multiple active moieties and strategic engineering of coordinated interfacial junctions are crucial for optimizing the reaction kinetics and intrinsic activities of heterogeneous electrocatalysts. Herein, a simple integrated heterostructure of biphasic Co0.7Fe0.3/Fe3C embedded on in situ grown N‐doped carbon sheets is constructed. Rationally designed CoFe/Fe3C‐T2 owns more accessible active sites and interfacial junction effects, cooperatively boosting the electron and mass transfer, needed for multifunctional electrocatalysis. Leveraging the synergistic effect of dual active sites, CoFe/Fe3C‐T2 demonstrates outstanding oxygen electrocatalytic activity in alkaline medium with an ultra‐low potential gap of 0.58 V, surpassing the recently available state‐of‐the‐art catalysts. Moreover, CoFe/Fe3C‐T2 air‐electrode achieves a high peak power density of 249 mW cm−2, a large specific capacity of 808 mAh g−1 and excellent cycling stability for aqueous Zn‐air batteries. Remarkably, the solid‐state flexible ZAB also exhibits satisfactory performance, showcasing an open‐circuit voltage of 1.43 V and a peak power density of 66 mW cm−2. These outstanding results push this catalyst to the top of the list of non‐noble metal‐based electrode materials. This work offers a viable method for using the active‐site‐uniting strategy to create double‐active‐site catalysts, which may find real‐time applications in energy conversion/storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Large area, 2D β-Ni(OH) 2 , < 3 nm thin nanosheets synthesized at water–air interface. • Device shows 820 mAh.cm−3 capacity with 70% retention after 30,000 cycles. • Device achieved ultrahigh energy density of 0.33 Wh.cm−3 at 275.86 W.cm −3. • β- Ni(OH) 2 shows enhanced OER activity η 10 :308 mV with Tafel value of 42 mV dec-1. • After charge storage & OER, XPS analysis confirms structural stability of the film. Bifunctional electrode materials are highly desirable for meeting increasing global energy demands and mitigating environmental impact. However, improving the atom-efficiency, scalability, and cost-effectiveness of storage systems, as well as optimizing conversion processes to enhance overall energy utilization and sustainability, remains a significant challenge for their application. Herein, we devised an optimized, facile, economic, and scalable synthesis of large area (cm2), ultrathin (∼2.9 ± 0.3 nm) electroactive nanosheet of β-Ni(OH) 2, which acted as bifunctional electrode material for charge storage and oxygen evolution reaction (OER). The β-Ni(OH) 2 nanosheet electrode shows the volumetric capacity of 2.82 Ah.cm−3(0.82 µAh.cm−2) at the current density of 0.2 mA.cm −2. The device shows a high capacity of 820 mAh.cm−3 with an ultrahigh volumetric energy density of 0.33 Wh.cm−3 at 275.86 W.cm −3 along with promising stability (30,000 cycles). Furthermore, the OER activity of ultrathin β-Ni(OH) 2 exhibits an overpotential (η 10) of 308 mV and a Tafel value of 42 mV dec-1 suggesting fast reaction kinetics. The mechanistic studies are enlightened through density functional theory (DFT), which reveals that additional electronic states near the Fermi level enhance activity for both capacitance and OER. [ABSTRACT FROM AUTHOR]

Anode materials that exhibit high energy density, high power density, long life cycle, and better safety profile for lithium‐ion batteries are necessary for the development of electric vehicles. Computational and experimental studies to describe the relevant aspects of carbon allotropes as anode materials are discussed, toward the significant improvement of specific power and energy capacity. The role of types of carbon ring and mixed hybridization (sp, sp2, and sp3) in carbon‐based anode materials for Li storage explored. An overview is provided on the procedures used to analyze the storage properties of anode materials using first‐principles theoretical methods such as intercalation energy, volume expansion, and open circuit voltage. Finally, the progress, importance, design, and the challenges of carbon‐based anode materials are comprehensively discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Same concentration of C 3 N and Graphene better for lowering the value of average OCV. • Charge transfer between Li and host depends on interface and site, helps to increase the stability and specific capacity. • Higher order structure shows the metallic behaviour. • Specific capacities in the range of 558 to 423 mAh-gm−1. • Low interlayer diffusion energy of Li-ion. The design and development of new and light weight two-dimensional (2D) heterostructures as anode materials to enhance the electrochemical properties for Li-ion batteries (LIB's) is a challenge. In this work, using first-principles study, we have demonstrated that the ratio of two-dimensional polyaniline (C 3 N) and graphene in the multilayer heterostructures plays a major role to define the Li storage properties and to provide metallicity for easy conduction of electrons. We have found that charge transfer between Li and the host depends on the interface and site, which helps in the improvement in specific capacity. The proposed heterostructures shows specific capacity varies from 558 mAh/gm to 423 mAh/gm. The specific capacity is high for heterostructures with more graphene in ratio which is correlated to higher charge accumulation in the host. Also, graphene helps to minimize the open-circuit voltage (OCV) of C 3 N and maintained an average of 0.4 V. The volume expansion for fully lithiated heterostructures is within 22 %. Li diffusion barrier energy varies in the range of 0.57 to 0.25 eV. The proposed 2D heterostructures could be a future material for anode in LIB's and the description of the interface effect on Li storage properties will help for further development of 2D heterostructure materials. [ABSTRACT FROM AUTHOR]

To cease the ever-increasing energy demand, additional enthusiastic focus has been given to generate more sustainable energy from alternative renewable sources. Storage of these energies for future usage solely banks on energy storage devices. A diversity of electrode materials based on two-dimensional (2D) transition metals and their derivatives have enticed the whole world owing to their tunable properties. Transition metal trichalcogenides (MX3 type) are the emergent class of 2D materials, which gathered a lot of interest because of their quasi-one-dimensional anisotropic properties with the van der Waals force of attraction in between the layers. Herein, TiS3 being a MX3-type of material is preferred as the battery type-supercapacitor electrode for energy storage applications with detailed theoretical predications and experimental validations. The highest capacitance attained for TiS3 is found to be 235 F/g (105 C/g) at 5 mV/s with a battery type of charge storage mechanism. The asymmetric hybrid device is fabricated using Ti3C2Tx MXene nanosheets as a negative electrode, and a brilliant 91% of capacitance retention is accomplished with an extensive potential window of 1.5 V. The investigational discoveries are substantiated by theoretical simulation in terms of the quantum capacitance assessment and charge storage mechanisms. [ABSTRACT FROM AUTHOR]

The Ostwald process, which is producing HNO3 for commercial use, involves the catalytic oxidation of NH3 and a series of chemical reactions conducted under severe operating conditions. Due to their energy‐intensive nature, these activities play a major role in greenhouse gas emissions and global energy consumption. In response to the urgent requirements of the global energy and environmental sectors, there is an increasingly critical need to develop novel, highly efficient, and environmentally sustainable methods. Herein, CoPc/C3N4 electrocatalyst, integrating CoPc nanotubes with C3N4 nanosheets, is shown. The CoPc/C3N4 electrocatalyst demonstrates yield rate of 871.8 µmol h−1 gcat−1 at 2.2 V, with corresponding Faradaic efficiency (FE) of 46.4% at 2.1 V, which notably surpasses that of CoPc. Through a combination of experimental investigations and density functional theory (DFT) calculations, this study shows that CoPc anchored on C3N4 effectively simplifies the adsorption and activation of chemically inactive nitrogen molecules. The improved catalytic activity for composite system may be the reason of re‐distribution of charges over the CoPc, tuning the valence orbital of Co center due to the presence of 2D layer of C3N4. This mechanism significantly lowers the energy barrier required for critical breaking of inert N2, ultimately leading to a significant improvement in N2 oxidation efficiency. [ABSTRACT FROM AUTHOR]

Widely used precious metal (i.e., Pt, or Pd) electrocatalysts need to be replaced with other cost-effective and earth-abundant materials for economical water splitting applications. Recently, two-dimensional (2D) transition metal dichalcogenides (MoS2, VS2, WS2, etc.) have emerged as ideal electrocatalysts for the hydrogen evolution reaction (HER) due to their tunable physicochemical properties and rich catalytic active sites. In this regard, we propose a strategy to achieve improved HER performance of VS2 by fabricating a hybrid material with transition metal (Zn and Cd)-based sulfides. A facile hydrothermal approach is employed to prepare a VS2/ZnS/CdS hybrid catalyst that exhibits remarkable electrocatalytic performance for the HER in acidic media with a small overpotential of 86 mV at 10 mA/cm2 and a Tafel slope of 74.4 mV/dec. This inferred the Volmer–Heyrovsky mechanism with electrochemical desorption of hydrogen as the rate-limiting step. High performance is attributed to the abundance of catalytically active sites and the synergistic interactions between the materials. Theoretical calculations reveal that the VS2/ZnS/CdS hybrid shows favorable HER activity owing to its low hydrogen adsorption free energy of about 0.35 eV. We believe that this work on designing 2D VS2/ZnS/CdS will offer a new pathway to discover an efficient H2 generation electrocatalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • S-dopant and S-linkers are exploited to tune the catalytic activity of GQD. • Charge transfer from active sites play an important role to bind the intermediates. • Higher efficiency of sulfurized GQD with double S dopant or in presence of oxygen. • Combined effect of S-linker and N-dopant enhances ORR efficiency of entangled GQDs. To enhance the catalytic efficiency of graphene quantum dot (GQD) for ORR, the role of S-dopant and S-linker is explored here by utilizing the first-principles density functional theory-based approach. The ORR efficiency is found to be changed on different active sites with the variation of dopant position and dopant configuration on the sulfurized GQD. Charge transfer from the dopant site to the active sites and to the intermediates, as well as the binding energy of intermediates on the active sites play an important role to realize the potential determining step, onset potential and the overpotential for ORR. The increase in the doping concentration of S or the presence of oxygen is found to drastically enhance the ORR efficiency of GQD. Furthermore, S-linkers are exploited to connect two GQDs entangled or twisted with each other and resulting in a rather complex system. The combined effect of entangling, S-linkers and presence of a single N dopant at the meta position of the active site resulted in the adsorption of the intermediates with optimum binding strength. Consequently, the ORR activity is found to be enhanced, thereby resulting in a metal-free and cost-effective electrocatalyst with efficiency similar to the Pt-based metal catalysts. [ABSTRACT FROM AUTHOR]

Being a macrolide antibiotic, the antiviral and anti-inflammatory properties of azithromycin (AZM) were taken advantage of during the COVID-19 pandemic which led to the overuse of AZM resulting in excessive release and accumulation in the waterways and ecosystem causing unpleasant threats to humankind. This demands the necessity for a highly sensitive material being capable of recognizing AZM in wastewater. Mindful of the optical attributes of organic ligand structures, we have constructed a hybrid material by chelating Zn2+ with pyridyl benzimidazole (PBI). The prepared sensor material ZnPBI was characterized using various microscopic and spectroscopic techniques including XRD, FT-IR, HR-SEM, HR-TEM, etc. The proposed sensor material exhibited proficient detection performance selectively towards AZM with a very low detection limit of 72 nM. Two linear ranges between 0 – 70 μM and 70–100 μM were observed corresponding to two different mechanistic pathways. To the best of our knowledge, the utilization of a metal-organic complex (MOC) for the fluorometric detection of AZM has not been explored so far. It is creditworthy to cite that the long-term structural stability of the sensor material was maintained for 100 days in water and it can be reused three times without any depreciation in the sensing activity. A combination of energy transfer routes, adsorption and electrostatic interactions for AZM detection are described experimentally and theoretically which provides insights into the role of MOC as sensing probes. [Display omitted] • A robust and luminescent organic-inorganic hybrid is developed. • The photo-physical and photo-chemical attributes of the hybrid are explored. • The fluorescent probe selectively recognizes azithromycin in water medium. • A remarkable quenching response was significant towards azithromycin. • A very low detection limit of 72 nM is achieved. [ABSTRACT FROM AUTHOR]

To restrain fossil fuel depletion, the need of the hour is the development of efficient, durable, and non-precious electrocatalysts for the hydrogen evolution reaction (HER). The hierarchical nanostructure consisting of transition metal dichalcogenides and graphitic heteroatom-doped carbon with an abundant interfacial M–N–C catalytic site is highly demanding for electrolytic applications. Herein, we report crystallinity-engineered ultrathin MoS 2 nanosheets hierarchy over nitrogen-doped graphitic carbon (NC) hollow spheres as a promising material for HER. The well optimized NC@MoS 2 demonstrates superior HER activity with a low onset overpotential of 9 mV and an overpotential of 145 mV at a current density of −10 mA cm−2. It exhibits low Tafel slope of 39 mV dec−1 and excellent chronoamperometric stability. Superior HER activity originates from interfacial Mo–N–C bonds. Density functional theory (DFT) calculations unveil that Mo–N–C bonds between MoS 2 and NC matrix ease electronic transportation and further diminish Gibbs free energy for HER. [Display omitted] • Hierarchy of MoS 2 Nanosheets (NSs) and polymer (PNMA) hollow spheres was realized. • Annealing altered crystallinity and convert of PNMA to N-doped carbon (NC). • Mo–N–C bond at interface of NC Matrix and MoS 2 NSs eased charge transfer for HER. • Distinctive morphology of hybrid and NC provided more accessible catalytic site. • Durability in acidic electrolytes makes the hybrid a potential electrocatalyst. [ABSTRACT FROM AUTHOR]

High-pressure behavior of the technologically important compound NiNb2O6 adopting a columbite-type orthorhombic structure at ambient pressure and temperature conditions was investigated using synchrotron x-ray powder diffraction, Raman spectroscopic measurements, and first-principles calculations. The x-ray diffraction data indicate the occurrence of irreversible pressure-induced structural phase transition in the studied compound beyond 9 GPa. The high-pressure phase is found to be monoclinic with space group P2/m. The large volume collapse (∼4.4%) at the transition indicates the nature of the transition to be of the first order. There is a change in oxygen anion coordination number around Nb from 6 to 8; however, the coordination number around Ni remains 6. The experimental pressure–volume data when fitted to the Birch−Murnaghan equation of states yield the value of ambient pressure bulk modulus (B 0) as 178.7 (17) GPa for the orthorhombic phase and 244 (6) for the high-pressure monoclinic phase. The changes in Raman spectra indicate the distortion of NbO6 octahedra resulting in structural phase transitions. The logarithmic variation of unit cell volume (V) with optical lattice mode frequency (ν) helped us to calculate their respective Grüneisen parameters (γ) and it also supports the instability of the orthorhombic columbite structure of NiNb2O6 beyond 9 GPa, originated due to strong octahedral deformation of NbO6 octahedra. The variation of structural, electronic, and optical properties with pressure has also been discussed through first-principles calculations based on density functional theory using the revised Perdew–Burke–Ernzerh of generalized gradient approximation. The theoretical bandgap collapses and the distortion of NbO6 octahedra through the O chains with pressure are emphasized from the density of states data. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity of T6[100] surface containing both sp 3 (C 1 ) and sp 2 (C 2 ) hybridized carbon atoms is explored using first-principles density functional theory based approach. The top layered C 1 atom of the surface is found to be more active towards the oxygen reduction reaction (ORR), as compared to that of C 2 atom. This is attributed to the presence of dangling σ bond in the corresponding C 1 atom, leading to the high electron density near the Ferrmi level. Whereas, the π electron in the top layered C 2 atom forms a weak out of plane network. As estimated from free energy profile, the overpotential is much lower when C 1 is considered as the active site and the final step i.e desorption of final OH − ion is found to be the potential determining step. We have also reported the effect of Si dopant on the catalytic activity of T6[100] surface and explained the origin of high overpotential value in this case. Thus in this report, we propose a new metal-free catalyst i.e T6[100] surface, having both sp 2 (maintains the high metallicity needed to reduce ohmic loss) and sp 3 (helps in capturing the upcoming molecules) hybridized carbon atoms, as a potential candidate for ORR. [ABSTRACT FROM AUTHOR]

Microstructural NiO–SnO2 nano-ceramic matrix was synthesized via a solgel auto-combustion technique with a perspective to investigate its noteworthy electric field emission and temperature-induced conduction anomaly. Exceptional field emission performance of nickel-tin oxide composites was discovered with a low turn-on field of 3.9 V/μm and a threshold field of 5.30 V/μm with a good field emission current density of 110.44 μA/cm2 and current stability. Density functional theory was employed to estimate its local work function (Φ) 3.365 eV, and the field enhancement factor (β) was obtained as 1570 by Fowler–Nordheim plot. The anomalies in conductivity spectra at 523 K were detected by a number of physical properties measurement including impedance, conductivity, dielectric, and differential scanning calorimetry with thermal expansion. These phenomena can be rationalized in terms strain-dependent thermal hysteresis effects and localized/delocalized e g electron with a transition from inferior conductive linkage [Ni2+–O2−–Ni2+] and [Sn2+/Sn4+–O2−–Sn2+/Sn4+] to higher conductive linkage [Ni2+–Ni3+] and [Sn2+–Sn4+] of coupled NiO–SnO2 matrix. The temperature dependence frequency exponent (n), ln τ, Rg, Rgb, Cg, and Cgb support additionally the conduction anomaly behavior, and the variation of dielectric constant (ɛr) and loss (tan δ) with temperature around 523 K has been explained in terms of the reduction of space charge layers due to reversal movement of delocalized e g electrons from the grain boundary limit. The frequency dispersing impedance, conductivity, and dielectric spectra with elevated temperature were also demonstrated to comprehend its conduction mechanism with theoretical correlation. [ABSTRACT FROM AUTHOR]

The major limitation of using graphene as a potential spacer element in interlayer exchange coupling (IEC) might be due to destruction of ferromagnetism as a result of the charge transfer effect at the interface if a transition metal based ferromagnetic layer is grown on the graphene surface. To overcome this problem, we have used the antiferromagnetic Ni(OH)2 layer grown on the graphene surface to convert it ferromagnetic due to the charge transfer effect. By growing thin layers of Ni(OH)2 on both sides of the graphene surface, strong antiferromagnetic IEC with ultralow coercivity (7 Oe) is observed. By lowering the nickel content, an ultrathin layer of Ni(OH)2 is grown on either side of graphene and shows complete ferromagnetism with a giant coercivity of 4154 Oe. Ab initio calculations have been done to substantiate this kind of charge transfer effect at the interface of Ni(OH)2 and graphene. Magnetotransport of the composite material is also investigated to understand the role of IEC in transport properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Engineered carbon-vacant CN (FCN) using formalin-assisted thermal polymerisation. • FCN achieved complete removal of Tetracycline via sonophotocatalysis within 60 min. • Boosted charge separation and extended visible light response over defected FCN. • Adsorption of oxygen molecules on FCN site resulted in abundant reactive species. Metal-free polymeric graphitic carbon nitride (CN) materials are robust and stable visible-light-driven photocatalysts that have recently piqued interest in photocatalytic applications. Its photocatalytic performance is restricted remarkably due to moderate oxidation ability and fast charge carrier recombination rate. To address these issues, we engineered carbon-vacant CN (FCN) using a facile formalin-assisted thermal polymerization of molten CN precursor in which the carbon vacancies (Cv) were regulated by altering formalin dosage. Consequently, FCN catalysts revealed Cv concentration-dependent sonophotocatalytic degradation of Tetracycline (TC) antibiotics over diverse water matrices. The optimal FCN exhibited complete TC degradation efficiency within 60 min with a synergy index of 1.4, which is approximately 2.6 times higher than that of pristine CN. The enhanced sonophotocatalytic performance was mainly due to the synergistic effect of ultrasound and light irradiation. The Cv formation also resulted in enhanced charge carrier transportation and facilitated oxygen adsorption at the Cv site of FCN - supported by both experimental study and theoretical calculation. Subsequently, FCN generated abundant reactive active oxygen species including, •O 2 – , as well as indirectly •OH which played a significant role in the degradation pathway and mineralisation of the TC molecules. This study provides insight into understanding the correlation between controllable defects and sonophotocatalytic degradation properties of the self-doped and deficient FCN. [ABSTRACT FROM AUTHOR]

• Design of single-metal dual site catalysts (SM-DSCs) for CO oxidation via LH mechanism. • Split d-orbital band center as a descriptor to estimate the chemisorption trends. • Brønsted−Evans−Polanyi (BEP) relations are proposed to identify the energy barriers. • PtBN2op and AgBN2 are the best catalysts for CO oxidation through LH mechanism. CO production has grown throughout time because of unwanted chemical reactions; therefore, the design of efficient and stable catalysts with minimal metal loading is in demand in the automobile industry for CO oxidation. Herein, density functional theory is used to study the CO oxidation mechanism on single-atom catalysts (SACs) and metal-boron centered single metal dual site catalysts (SM-DSCs). It is observed that CO oxidation could follow Eley-Rideal (ER) mechanism on single-atom catalysts, such as MN4, MN3, MN2, and MN2op systems, where M is a 3d transition metal. Whereas in the case of SM-DSCs, the inclusion of Boron will make the Langmuir-Hinshelwood (LH) mechanism possible over ER mechanism with less chance of CO poisoning. The Brønsted−Evans−Polanyi (BEP) relations are proposed (as a function of oxygen atom binding) to identify the energy barriers (Ea 1 and Ea 2) for the release of the first and second CO 2 and O 2 adsorption energies for any new SM-DSCs system. Further microkinetic model is implemented on 30 SM-DSCs and found that PtBN2op and AgBN2 SM-DSCs own best catalytic activity with high Sabatier activity and Turnover frequency for CO 2 production. Hence, this work provides an approach toward the possibility of LH mechanism in the class of single-metal atom-based catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

To overcome the detrimental effect of charge transfer from a transition metal to 2D substrates like graphene, we have grown ultrathin antiferromagnetic α-Fe2O3 layers on both sides of the graphene surface. Anomalous magnetic behavior, viz., coercivity and exchange bias, increases with increasing temperature with strong ferromagnetic ordering. The highest values of coercivity and large exchange bias are obtained as 3335 Oe and 2361 Oe, respectively. Large enhancement (646%) in exchange bias is observed with an increase in temperature from 2 K to 70 K. Interlayer exchange coupling between the ferromagnetic layers becomes strongest at 300 K to achieve an ultralow coercivity of 22 Oe by growing an α-Fe2O3 phase on both sides of the graphene surface. A 32% negative magnetoresistance is observed as a result of exchange bias which changes with temperature. All these results are explained on the basis of the charge transfer effect at the interface of the graphene/α-Fe2O3 nanostructure at the low temperature region and the spin canting effect of surface states at the higher temperature region. Theoretical Density Functional Theory calculation is also done to understand the interface interaction, quantitative evaluation of charge transfer, and density of states. [ABSTRACT FROM AUTHOR]

Conjugated polymers and titanium-based metal-organic framework (Ti-MOF) photocatalysts have demonstrated promising features for visible-light-driven hydrogen production. We report herein a strategy of anisotropic phenanthroline-based ruthenium polymers (PPDARs) over Ti-MOF, a tunable platform for efficient visible-light-driven photocatalytic hydrogen evolution reaction (HER). Several analytical methods including X-ray absorption spectroscopy (XAS) revealed the judicious integration of the surface-active polymer over the Ti-MOF reinforcing the catalytic activity over the broad chemical space. PPDAR-4 polyacrylate achitecture led to a substantial increase in the H2 evolution rate of 2438 µmolg−1h−1 (AQY: 5.33%) compared to pristine Ti-MOF (238 µmol g−1 h−1). The separation of photogenerated charge carriers at the PPDAR-4/Ti-MOF interface was confirmed by the optical and electrochemical investigations. The experimental, as well as theoretical data, revealed their physical and chemical properties which are positively correlated with the H2 generation rate. This offers a new avenue in creating polymer-based MOF robust photocatalysts for sustainable energy. Combining conjugated polymers with transition-metal-based metal-organic frameworks offers an opportunity to produce efficient photocatalytic materials. Here, exposed active sites and efficient charge transfer lead to hydrogen evolution rates of up to 2438 µmol g−1 h−1 for composites of anisotropic phenanthroline-based ruthenium polymers grafted on titanium-based MOFs. [ABSTRACT FROM AUTHOR]

The growing demands for ammonia in agriculture and transportation fuel stimulate researchers to develop sustainable electrochemical methods to synthesize ammonia ambiently, to get past the energy-intensive Haber-Bosch process. However, the conventionally used aqueous electrolytes limit N2 solubility, leading to insufficient reactant molecules in the vicinity of the catalyst during electrochemical nitrogen reduction reaction (NRR). This hampers the yield and production rate of ammonia, irrespective of how efficient the catalyst is. Herein, we introduce an aqueous electrolyte (NaBF4), which not only acts as an N2-carrier in the medium but also works as a full-fledged "co-catalyst" along with our active material MnN4 to deliver a high yield of NH3 (328.59 μg h-1 mgcat-1) at 0.0 V versus reversible hydrogen electrode. BF3-induced charge polarization shifts the metal d-band center of the MnN4 unit close to the Fermi level, inviting N2 adsorption facilely. The Lewis acidity of the free BF3 molecules further propagates their importance in polarizing the N≡N bond of the adsorbed N2 and its first protonation. This push-pull kind of electronic interaction has been confirmed from the change in d-band center values of the MnN4 site as well as charge density distribution over our active model units, which turned out to be effective enough to lower the energy barrier of the potential determining steps of NRR. Consequently, a high production rate of NH3 (2.45 × 10-9 mol s-1 cm-2) was achieved, approaching the industrial scale where the source of NH3 was thoroughly studied and confirmed to be chiefly from the electrochemical reduction of the purged N2 gas. [ABSTRACT FROM AUTHOR]

Green synthesis of urea under ambient conditions by electrochemical co‐reduction of N2 and CO2 gases using effective electrocatalyst essentially pushes the conventional two steps (N2 + H2 = NH3 and NH3 + CO2 = CO(NH2)2) industrial process at high temperature and high pressure, to the brink. The single step electrochemical green urea synthesis process has hit a roadblock due to the lack of efficient and economically viable electrocatalyst with multiple active sites for dual reduction of N2 and CO2 gas molecules to urea. Herein, copper phthalocyanine nanotubes (CuPc NTs) having multiple active sites (such as metal center, Pyrrolic‐N3, Pyrrolic‐N2, and Pyridinic‐N1) as an efficient electrocatalyst which exhibits urea yield of 143.47 µg h–1 mg–1cat and faradaic efficiency of 12.99% at –0.6 V versus reversible hydrogen electrode by co‐reduction of N2 and CO2 are reported. Theoretical calculation suggests that Pyridinic‐N1 and Cu centers are responsible to form CN bonds for urea by co‐reduction of N2 to NN* and CO2 to *CO, respectively. This study provides the new mechanistic insight about the successful electro‐reduction of dual gases (N2 and CO2) in a single molecule as well as rational design of efficient noble metal‐free electrocatalyst for the synthesis of green urea. [ABSTRACT FROM AUTHOR]

We have studied using density functional theory and non-equilibrium Green's function based approach, the electronic structures of 555-777 divacancy (DV) defected armchair edged graphene nanoribbons (AGNR) as well as the transport properties of AGNR based two-terminal devices constructed with one defected electrode and one N doped electrode. Introduction of 555-777 DV defect into AGNR results in shifting of the π and π* bands towards the higher energy value indicating a downward shift of the Fermi level. Formation of a potential barrier, analogous to that of conventional p-n junction, has been observed across the junction of defected and N-doped AGNR. The two terminal devices show diode like property with high rectifying efficiency for a wide range of bias voltages. The devices also show robust negative differential resistance with very high peak-to-valley ratio. Shift of the electrode energy states and modification of the transmission function with applied bias have been analyzed, in order to gain an insight into the nonlinear and asymmetric behavior of the current-voltage characteristics. Variation of the transport properties on the width of the ribbons has also been discussed. [ABSTRACT FROM AUTHOR]

Producing molecular hydrogen (H2) using water provides a sustainable approach for developing clean energy technologies. Herein, we report highly active ruthenium (Ru) clusters supported on iron oxide (Ru/Fe3O4) and Fe3O4/multi-walled carbon nanotubes (Ru/Fe3O4/MWCNTs) by simple electrochemical deposition in a neutral aqueous medium. The supported catalyst exhibits good hydrogen evolution reaction (HER) activity in an acidic environment. Cyclic voltammograms (CVs) of potassium ferrocyanide (K4[Fe(CN)6]) confirm that MWCNTs enhance the electron transfer process by decreasing the redox formal potential. The overpotentials of Ru/Fe3O4/MWCNTs and Ru/Fe3O4 electrocatalysts versus the reversible hydrogen electrode (RHE) were found to be 101 mV and 306 mV to reach a current density of 10 mA cm−2. As prepared, the catalyst displays good stability and retain its HER activity even after 1000 cycles. Furthermore, the stability of Ru/Fe3O4/MWCNTs was studied using the chronopotentiometric (CP) technique for 12 h and found negligible loss in the catalytic activity towards the HER. To explore the role of Ru and underneath MWCNTs in improving the catalytic performance of Fe3O4, density functional theory (DFT) calculations were carried out. DFT calculations indicate that the octahedral site of Ru/Fe3O4 favors the HER with a low overpotential. However, Ru/Fe3O4/MWCNTs are more efficient towards the HER, which could be due to the availability of both octahedral and tetrahedral catalytic sites. [ABSTRACT FROM AUTHOR]

[Display omitted] The exclusive characteristic properties of two-dimensional (2D) materials have enticed most of the researchers and scientific community to employ a plethora of pioneering stratagems in order to puzzle out modern-day problems. Some of the possibilities are currently are at theoretical phases, while some of them are well-explored experimentally. Nanoribbon-like structures of the 2D materials are ancillary entrants for 2D nanosheets with tunable and enhanced properties. Protuberant properties like abundant and highly exposed active sites on the edges facilitated electron transfer, and superior charge mobility, etc. make them poles apart from their bulk counterparts. Nowadays, these nanoribbon-like structures are contributing to countless applications such as solar cells, photodetectors, sensing, field emission, energy storage, and catalysis. Accordingly, we have put an overview of recent advancements in the properties, preparations, and applications of nanoribbon-like structures based on 2D materials. The contemporary review thoroughly recapitulates the numerous properties of nanoribbon-like materials including crystal structure, bandgap, optical, electrical, magnetic, and catalytic properties. Moreover, the review also addresses the tuning approaches used to optimize the properties of nanoribbon materials. The most recent synthesis approaches used for the preparation of nanoribbon-like structures are also highlighted along with their exceptional implementation in various intriguing applications. Furthermore, this comprehensive review put the finishing touches on a discussion of the present-day outlook and some of the crucial scientific challenges which have to be addressed to improve the performances of nanoribbons of 2D materials-based devices. [ABSTRACT FROM AUTHOR]

Eight electron nitrate (NO 3 –) reduction to ammonia (NH 3) offers a cost–effective and energy efficient route than the Haber–Bosch process. The state of art electrocatalysts for nitrate reduction shows potential activity, albeit suffering from poor Faradaic efficiency, kinetically sluggish multi electron–proton process, and competitive hydrogen evolution reaction. Herein, we present a hollow iron phthalocyanine (FePc) rectangular nanotube (RNTs) electrocatalyst with 100 % Faradaic efficiency and 35067.09 µg h–1 mg cat –1 ammonia yield, which is 3.5 times higher than that of FePc nanorods. One-of-a-kind hollow nanostructure has Fe-N 4 active motif sites necessary for NO 3 – activation, dissociation, specific intermediate formation, and interaction, resulting in the energy-efficient generation of NH 3 , according to in-situ research combined with theoretical analysis of molecular scale reaction mechanism. These unique results, coupled with the monitoring of pH changes in real time during electrolysis, open up new possibilities for progressive ammonia production with reduced carbon footprint. [Display omitted] ● The hollow iron phthalocyanine (FePc) rectangular nanotube (RNTs) showed the ammonia yield ∼35 mg h–1 mg cat –1 and 100 % Faradaic efficiency respectively. ● The high-performance activities of NO 3 RR by FePc nanotube is confirmed by several experiment with DFT based theoretical analysis. ● The video graphic demonstration of the pH change in the electrolyte solution from 6 to 12 during NO 3 RR further confirms the production of ammonia for practical utility. [ABSTRACT FROM AUTHOR]

Summary: Using first‐principles calculations, we investigate a family of doped graphene nanoribbons (GNRs) for their suitability as cathode hosts in lithium‐sulfur batteries. We probe the role played by the lone pairs of the dopants in confining the lithium polysulfides (LiPS) to understand the mechanism of binding. Our results show that the Li bond between the polysulfides and the doped GNRs is analogous to a hydrogen bond and also dipole‐dipole interactions play a key role in anchoring the polysulfides. A critical donor‐Li‐acceptor angle of 180° is found to be essential for proper adsorption of LiPS, highlighting the importance of the directionality of lone pairs. The charge lost by the sulfur atom of the polysulfide upon adsorption and shape of the lone pair basins and the value of Electron Localization Function (ELF) at the dopant position can provide a quick estimate of the strength of the bond. Significant contractions in the ELF profiles are also observed upon Li2S adsorption, further providing evidence for the hydrogen bond‐like nature of the Li bond. Our results corroborate the fact that all acceptors capable of forming hydrogen bonds can be employed as suitable dopants for carbon‐based cathode hosts in Li‐S batteries. [ABSTRACT FROM AUTHOR]

In this work, we report a cost-effective electro-catalyst for oxygen reduction reaction (ORR) by developing a composite between graphene oxide and carbon nanotubes and simultaneously doping with a nitrogen atom. The nitrogendoped carbon nanotube/graphene oxide composites were prepared by chemical oxidation method followed by annealing process. Such composite enhances the active adsorption sites, electrical conductivity and corrosion resistance leading to better impact toward ORR. The N-graphene oxide/functionalized carbon nanotube catalyst that furnishes both pyridinic-N and pyridinic-N-O (or oxidic-N) shows higher efficiency toward electrocatalytic ORR performance in alkaline conditions. More interestingly, as-prepared electrocatalyst shows durability test up to 20 000 potential cycles without loss in its half-wave potential (Ehalf) while commercial Pt/C catalyst shows a huge loss in Ehalf value under similar conditions, indicating sustainability in the performance of former, especially compared to the reported metal or metal-free electrocatalysts. The origin of high catalytic activity of oxidic-N is correlated with π-electron density at the Fermi level studied by density functional theory and considered as an electronic descriptor. [ABSTRACT FROM AUTHOR]

[Display omitted] The burst of energy produced from the sustainable energy sources need to be harnessed by energy storage systems. Development of novel and advanced energy storage devices such as supercapacitors discover an enormous future ahead. Recently, hybrid supercapacitors (electric double layer capacitor (EDLC) and pseudocapacitors) trend to be used as energy storage interfaces for their improved efficacy in energy density without altering the power density. In the ongoing workplan, transition metal selenides MnSe 2 and its hybrid with multiwalled carbon nanotubes (MWCNTs) are synthesized by a simplistic hydrothermal protocol. Certainly, cubic phases of MnSe 2 -MWCNT(MS/CNT) manifested superior electrochemical performance in both symmetric and asymmetric full cell configurations in contrast to prestine MnSe 2 (MS). The asymmetric MS/CNT cell achieved an excellent charge storage capability with an high energy density of 39.45 Wh kg−1 at a power density of 2.25 kW kg−1 maintaining an energy density of 14.5 Wh kg−1 at a high power density of 4.5 kWh kg−1 and also revealed long term stability over 5000 consecutive charge/discharge cycles (capacitance retention of 95.2%). Furthermore, the preferable growth along (2 0 0) direction in the presence of MWCNTs favoured in enriching the supercapacitive property of MS. The quantum capacitance of MnSe 2 surfaces and MS/CNT heterostructure has been estimated using density functional theory simulation to confirm the experimental outcomes. Theoretical investigation simultaneously exposed the contribution of (2 0 0) plane of MnSe 2 and MWCNTs cultured in enhanced DOS (density of states) near the Fermi level that remarkably promoted the energy storage efficiency of MS/CNT. [ABSTRACT FROM AUTHOR]

Development of an inexpensive electrocatalyst for hydrogen evolution (HER) and oxygen evolution reactions (OER) receives much traction recently. Herein, we report a facile one-pot ethyleneglycol (EG) mediated solvothermal synthesis of orthorhombic Co 2 P with particle size ~20–30 nm as an efficient HER and OER catalysts. Synthesis parameters like various solvents, temperatures, precursors ratios, and reaction time influences the formation of phase pure Co 2 P. Investigation of Co 2 P as an electrocatalyst for HER in acidic (0.5 M H 2 SO 4) and alkaline medium (1.0 M KOH), furnishes low overpotential of 178 mV and 190 mV, respectively to achieve a 10 mA cm−2 current density with a long term stability and durability. As an OER catalyst in 1.0 M KOH, Co 2 P shows an overpotential of 364 mV at 10 mA cm−2 current density. Investigation of Co 2 P NP by XPS analysis after OER stability test under alkaline medium confirms the formation of amorphous cobalt oxyhydroxide (CoOOH) as an intermediate during OER process. [Display omitted] • Co 2 P nanoparticles synthesized by one step solvothermal method. • HRTEM confirms the formation of nanoparticles with ~20–30 nm in size. • The Co 2 P catalyst exhibits high catalytic activity for HER and OER. • Co 2 P electrode shows excellent stability and durability during HER and OER. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mixed metal oxide & borate heterostructure over exfoliated graphite foam is presented. • Nitrogen doped support and supported catalyst interaction leads to excellent catalytic activity. • Large enhancement in OER catalytic activity due to electronic tuning of support via N-doping. • Outstanding durability at high current density 300 mA cm−2 over 10 h is demonstrated. Support-catalyst interface plays a critical role in electrocatalytic processes as the rates of involved reactions are directly linked with the interfacial charge transfer efficiency. Here, we are presenting nitrogen doped exfoliated graphite foil (NGF) as the 3D support which offers electronically coupled interface to catalytic heterostructure comprises of nickel-iron based oxide and its borate. As developed hybrid (NGF/NiFe/Borate) show excellent oxygen evolution reaction (OER) under alkaline condition with low overpotential of 281 mV at current density of 10 mA cm−2 and Tafel slope 62 mv dec−1. The results beat most nonprecious metal catalysts and noble commercial IrO 2 deposited over same NGF substrate with outstanding long-term durability over 10 h at high current density 300 mA cm−2. Efficient electron injection from NGF support and its low resistance leads to enhancement in current density by more than 136 % at operative potential of 1.55 V, in comparison to un-doped exfoliated graphite foil support. Beside electronically tuned support, high catalytic efficiency is also linked with planner growth of borate nanosheets that helps in fast interfacial charge transfer in its transverse direction to the catalytic site. Our work highlights the importance of electronic tuning of catalyst support to enhance the performance of supported borate catalyst and to rationally design low cost, highly active OER catalyst. [ABSTRACT FROM AUTHOR]