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[Display omitted] Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for the development of excellent bifunctional electrocatalysts, which are key functions in clean energy production. The emphasis of this study lies in the rapid design and investigation of 153 MN 4 –graphene (Gra)/ MXene (M 2 NO) electrocatalysts for ORR/OER catalytic activity using machine learning (ML) and density functional theory (DFT). The DFT results indicated that CoN 4 –Gra/Ti 2 NO had both good ORR (0.37 V) and OER (0.30 V) overpotentials, while TiN 4 –Gra/M 2 NO and MN 4 –Gra/Cr 2 NO had high overpotentials. Our research further indicated orbital spin polarization and d-band centers far from the Fermi energy level, affecting the adsorption energy of oxygen-containing intermediates and thus reducing the catalytic activity. The ML results showed that the gradient boosting regression (GBR) model successfully predicted the overpotentials of the monofunctional catalysts RhN 4 –Gra/Ti 2 NO (ORR, 0.39 V) and RuN 4 –Gra/W 2 NO (OER, 0.45 V) as well as the overpotentials of the bifunctional catalyst RuN 4 –Gra/W 2 NO (ORR, 0.39 V; OER, 0.45 V). The symbolic regression (SR) algorithm was used to construct the overpotential descriptors without environmental variable features to accelerate the catalyst screening and shorten the trial-and-error costs from the source, providing a reliable theoretical basis for the experimental synthesis of MXene heterostructures. [ABSTRACT FROM AUTHOR]

We employed density functional theory to investigate Co-N4/Gra single-atom catalysts, focusing on the modification of axial ligand (X=-F, -CN and -C3H4N2) and examined the influence of ligand field and electric potential on eNORR. Our results demonstrate that Co-N4[X]/Gra exhibit favorable thermodynamic adsorption (Δ G *NO < 0) and remarkable activation activity toward NO molecules. Co-N4/Gra demonstrates a limiting potential of −0.13 V with the potential-determining step (PDS) of *NH3 → * + NH3(g). Notably, under the introduction of ligands, Co-N4[F]/Gra achieves the most favorable overpotential of −0.07 V, superior to most of NORR electrocatalysts, and meanwhile shows an exceptional selectivity of 99.99% for eNORR compared to competitive hydrogen evolution reaction. Under the solvent environment, Co-N4/Gra features the triggering potentials of −0.33 V for a pH of 1, −0.71 V for a pH of 7, and −1.10 V vs RHE for a pH of 13, respectively. Additionally, the potential reduces the desorption energy and adsorption energy of NH3, facilitating the accessibility of the NH3 desorption step (PDS) and promoting NO reduction. Thus, under realistic conditions, the Co ion's active site displays variable valence electrons and forms a dynamic interplay with the ligand field effect, rendering a crucial effect on the adsorption of reaction species during the eNORR. [ABSTRACT FROM AUTHOR]

This study investigates the sensing of H 2 S and NH 3 over 2D nanosheets, namely graphene (GRA), boron nitride (BN), silicon carbide (SiC) and boron carbon nitride (BCN), using the first principle density functional theory. A CAM-B3LYP/6–31 G level of theory was used for all the computations and evaluation of the geometric and electronic properties. The optimized clusters indicated the chemisorption between the gas molecules and the SiC nanosheet. The Fourier transform infrared (FTIR) spectra were obtained to study the N-H and S-H shifts in the post-adsorption clusters. Based on the magnitude of the computed adsorption energies, SiC (-0.61 eV for the H 2 S cluster and −1.21 eV for the NH 3 cluster) was found to adsorb both the gas molecules most effectively. The electrostatic potential maps and the molecular orbitals' distribution were studied to investigate the electronic properties. The analysis showed that the adsorption of H 2 S and NH 3 over GRA, BN, and BCN was physical, whereas, on SiC, nanosheet chemisorption was observed. Atom-In-Molecule (AIM) analysis was carried out to account for the possible weak interactions. The study concluded that the SiC nanosheet was the most suitable for the adsorption of H 2 S and NH 3 gases. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing high efficient and cheap electrocatalysts for carbon dioxide reduction reaction (CO 2 RR) is the key to achieve CO 2 transformation into clean energy. Herein, a series of transition metal dimer and nitrogen codoped graphene (M 2 N 6 -Gra, M = Cr–Cu) acting as electrocatalysts for CO 2 RR are investigated based on the density functional method. For M 2 N 6 -Gra (M = Cr, Mn), the selectivity is poor and CO poisoning is serious. Fe 2 N 6 -Gra is the best CO 2 RR catalyst due to the good selectivity and catalytic activity. The calculated overpotential is very small, i.e., 0.03 V for COOH channel, 0.05 V for HCOO channel. Hydrogen evolution reaction is also refrained on the Fe 2 N 6 -Gra surface, which further supports its high catalytic performance. For M 2 N 6 -Gra (M = Co, Ni, Cu), the catalytic activity is poor due to large overpotentials. These results indicate that if designed carefully, the transition metal dimer and nitrogen codoped graphene would be good candidate for the high efficient and selective CO 2 RR catalyst. Image 1 • The mechanism of CO 2 RR on M 2 N 6 -Gra (M = Cr–Cu), has been studied by using the DFT. • The studied M 2 N 6 -Gra (M = Cr–Cu) is stable thermodynamically. • Fe 2 N 6 -Gra exhibits high selectivity and catalytic activity for CO 2 RR. [ABSTRACT FROM AUTHOR]

Recently, heteroatom co-doped carbon material catalysts have shown extraordinary oxygen reduction reaction (ORR) catalytic activity, but a lack of understanding of the specific mechanism of the ORR has hindered their further development. In this study, we studied the geometric structure, stability, electronic properties, catalytic sites and detailed ORR pathways of P, N co-doped graphene (PN-Gra) by density functional theory (DFT) calculations, trying to reveal the effect of N and P co-doped graphene on the catalytic activity of the ORR. Our calculations indicate that the PN-Gra structure remains stable at high temperature (1000 K) and P, N atoms with their adjacent four carbon atoms constitute the active region to adsorb O2 more efficiently than single phosphorus or nitrogen doped catalysts. Combining energy barrier and free energy diagram analysis, the most favorable pathway is O2* → O* + O* → OH* + O* → 2OH* → OH* + H2O → 2H2O, which is thermodynamically favorable and the associated energy barrier is low, with an overpotential of 0.96 V. After comprehensive analysis and comparison, P, N co-doping does improve the catalytic ability due to the synergistic effect compared to single doping. We believe that this study provides researchers a way to understand the reaction mechanism and ways to improve the catalytic properties of carbon-based materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The bifunctional catalytic mechanism of LaN x C 4-x -Gra for ORR and OER in acidic and alkaline environments was discussed for the first time. • OH modification is helpful to the improvement of catalytic activity for ORR, but adverse for OER. • LaN 2 C 2 hex-Gra exhibits potential bifunctional activity in alkaline environment and also shows excellent OER activity in acidic environment. • The descriptor f-band center was introduced to rapidly predict catalytic activity. The oxygen reduction/evolution reaction (ORR/OER) on oxygen electrode are the definitive reactions in charge/discharge process of fuel cells and metal air batteries. The research of bifunctional and acidic-alkaline omnipotent electrocatalysts for the oxygen electrode reaction is of great significance for the development and application of electrochemical storage and conversion technologies. In this paper, the catalytic performance of the rare earth LaN x C 4-x -doped graphene (LaN x C 4-x -Gra) catalysts has been discussed extensively. The results demonstrate that in the alkaline environment, LaN 2 C 2 hex-Gra exhibits potential bifunctional activity with the original ηOER is 0.68 V, and the ηORR is 0.56 V accompanied by OH ligands modified. Impressive, LaN 2 C 2 hex-Gra also shows excellent OER activity in acidic environment with the η of 0.68 V. Finally, the catalytic activity can be rapidly evaluated by scale relationship with the introduced band center, which will provide guidance for the development of efficient rare earth single atomic catalysts. [ABSTRACT FROM AUTHOR]

We investigated the effect of F and Cl functionalization of Janus ZnO on the optoelectronic propertiesof Graphene/ZnO (Gra/ZnO) heterojunctions by using Density Functional Theory (DFT). The calculated results show that the Janus ZnO/Gra heterojunction is a van der Waals heterojunction with layer spacing >3 Å for both stacking styles. In addition, the functionalized heterojunction retains the original structure of Gra and has an interface formation energy of <0, making it easy to prepare chemically. Furthermore, different stacking styles can convert heterojunctions from n-type Schottky to ohmic contacts, which has promising applications in field-effect transistors. Moreover, functionalized Janus ZnO/Gra can effectively enhance interlayer charge transfer and improve the transmittance of the heterojunction, which is beneficial for applications in nanoelectronic devices. [Display omitted] • We investigate F and Cl functionalization of janus ZnO on optoelectronics of Gra/ZnO. • We find the functionalized heterojunction retains the original structure of Gra. • We detect the janus ZnO/Gra heterojunction is a van der Waals heterojunction. • Functionalized janus ZnO/Gra can effectively enhance interlayer charge transfer. • Functionalized janus ZnO/Gra can improve the transmittance of the heterojunction. [ABSTRACT FROM AUTHOR]

This computational study explores the adsorption of volatile organic compounds (VOCs), namely 1,3-butadiene, benzene, indole and toluene, using graphene (GRA), boron nitride (BN) and boron carbon nitride (BCN) nanosheets. The optimized structures obtained from the density functional theory computations and their vibrational frequencies were used to investigate the nature of the adsorption interactions. Based on HOMO and LUMO distributions, the variation in the orbital distributions during the adsorption was studied. The non-covalent interaction isosurfaces and reduced density gradient scatter plots were also obtained to understand the interactions during adsorption. The post-adsorption orientations of the VOCs over GRA, BN and BCN were parallel to the plane of the nanosheets. The computations indicated increased van der Waals interactions between the VOCs and the adsorbent sheets. The analysis showed that the VOCs interact with the nanosheets through weak van der Waal forces and showed π-π stacking. The overall analysis showed that the order of adsorption of VOCs on the nanosheets was: GRA > BCN > BN. • Adsorption behaviour of GRA, BN and BCN nanosheets was examined towards 1,3-butadiene, benzene, indole and toluene. • The post-adsorption orientations of the VOCs over GRA, BN and BCN were parallel to the plane of the nanosheets. • The analysis showed that the VOCs interact with the nanosheets through weak van der Waal forces and shows π-π stacking. • The adsorption of VOCs on GRA, BN and BCN was accompanied by non-covalent interactions. • The analysis showed that the order of adsorption of VOCs on the nanosheets was: GRA > BCN > BN. [ABSTRACT FROM AUTHOR]

Using FeN 2 -gra as a single-atom catalyst to oxidize toxic CO into non-toxic CO 2. [Display omitted] • Different N and C atom configurations on FeN 2 -Gra have little effect on the thermodynamic stability of the structure and the gas adsorption performance. • The maximum energy barrier required for CO oxidation by FeN 2 -hex through LH mechanism is 0.270 eV, while the RLS of FeN 2 -opp and FeN 2 -pen are 0.673 eV and 0.697 eV, respectively. • The remaining O atom in the process of generating the second CO 2 are very easy to achieve, realizing the recycling of the catalyst. Single-atom catalysts (SACs) can maximize the utilization of metal atoms and reduce manufacturing costs, so they have been extensively studied. This study used density functional theory (DFT) calculations to discuss in detail the CO oxidation reaction (COOR) mechanism on non-noble metal iron and nitrogen atoms co-doped graphene. It was determined that FeN 2 -Gra is a suitable catalyst for the COOR due to its stable configuration, adsorption performance, kinetic analysis, and catalytic activity. The optimal path for FeN 2 -Gra on COOR is the LH mechanism, in which the lowest energy barrier that FeN 2 C 2 -hex needs to cross through the LH mechanism is 0.270 eV. The rate limiting steps (RLS) of FeN 2 C 2 -opp and FeN 2 C 2 -pen along the LH mechanism are 0.673 eV and 0.697 eV, respectively. According to the theoretical analysis, FeN 2 -Gra is a low-cost, high-efficiency catalyst suitable for COOR, which provides new ideas for subsequent experimental guidance and synthesis of ideal catalysts with superior catalytic performance. [ABSTRACT FROM AUTHOR]

We investigated the photoelectric properties of Graphene (Gra)/ZnO, Gra/Silicene (Si) and ZnO/Gra/Si heterostructures by using density functional calculations. The results show that ZnO, Gra and Si retain their respective electronic properties, which results from the van der Waals (vdW) interlayer interaction between the heterogeneous interfaces. We also can find that the band gap of ZnO: ZnO (1.67 eV) < Gra/ZnO (1.74 eV) < ZnO/Gra/Si (1.76 eV). ZnO/Gra/Si with sandwich structure has the best photoelectric performance. [ABSTRACT FROM AUTHOR]

Optimization of graphene-metal contact materials with excellent performance has motivated extensively studies of metal-graphene interactions. Metal/Graphene/Metal (M/Gra/M) complexes can be fabricated by intercalating foreign elements into interface between graphene and its substrate. As a result, intercalation has been proved to be the most efficient method to modify electronic property of graphene. By using density functional theory (DFT) calculations combined with quasi-atomic minimal basis orbitals (QUAMBOs) method, we systematically study interaction and electronic property of M/Gra/M sandwich complexes. Charge transfer and bond order analyses based on QUAMBOs approaches show that interaction between transition metal adatoms and graphene is much stronger than interaction between simple metal adatoms and graphene. Our calculated results suggest that magnetic moment is noticeable enhanced while electronic dipole moment is significantly reduced for M/Gra/M complexes. The increase of magnetic moment is mainly attributed to metal adatoms. Besides, the depletion of dipole moment is ascribed to anti-parallel electronic dipole moment in metal adatoms for high symmetry M/Gra/M sandwich complexes. We believe M/Gra/M sandwich structures can be of great interest for applications as spin transport and magnetic storage devices. [Display omitted] • Interaction between transition metals and graphene is covalent. • Interaction between simple metals and graphene is ionic. • Magnetic moment is enhanced and electronic dipole moment is reduced. • Increase of magnetic moment is attributed to metals with huge magnetic moments. • Depletion of dipole moment is ascribed to anti-parallel electronic dipole moment. [ABSTRACT FROM AUTHOR]

• The novel 1T-WSe 2 /Gra nanostructure was fabricated using ammonia-assisted synthesis. • The low electron localization allows ions to rapidly change the oxidation states of W atoms. • The 1T-WSe 2 /Gra exhibits an outstanding specific capacitance and energy density. Transition metal dichalcogenides (TMDCs) with electrocatalytic properties have become the focus in the energy storage field. However, the storage ability of TMDCs is considerably limited by their poor electrical conductivity, because the lamellar structure tends to form irreversible agglomerates after several cycles. Herein, an ammonia-assisted synthesis of a gypsophila-like 1T-WSe 2 /graphene is conducted. Through adjusting different growth conditions, the gypsophila-like nanostructure is controllable. Electrochemical measurements indicated that gypsophila-like 1T-WSe 2 /graphene exhibits an outstanding specific capacitance of 1735 F g−1 at 1 A g−1, and the 1T-WSe 2 /graphene all-solid-state supercapacitor shows ultrahigh energy density (48.2 Wh kg−1 at 250 W kg−1). After research, ammonium stabilizes the 1T phase, and generates a small amount of ammonia bubbles in the alkaline solution to prevent the structure collapsing during the electrode operation. Furthermore, the performed experiments and density functional theory (DFT) calculations confirm that a decrease in the electron localization near the Fermi level of 1T-WSe 2 enhances electrical conductivity, and the absorption capability of potassium by 1T-WSe 2 is three times that of 2H-WSe 2. The result shows the gypsophila-like 1T-WSe 2 /graphene is highly attractive for the development of advanced electrodes for energy storage devices. [ABSTRACT FROM AUTHOR]