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Nitrogen doped carbon functionalized CoSe2 nanowires (CoSe2@N–C NWs), which act as potential oxygen evolution reaction (OER) catalysts with a large current density and high stability have been reported. Owing to the collaborative optimization of electrical conductivity, free adsorption energy and binding strength of OER intermediates, the prepared CoSe2@N–C NWs exhibit an enhanced 6.61-fold catalytic activity compared to the pristine CoSe2 NW electrode in 1.0 M KOH solution at the overpotential of 340 mV. [ABSTRACT FROM AUTHOR]

The development of active and inexpensive electrocatalysts for the oxygen evolution reaction (OER) to promote water splitting has always been a major challenge. Cobalt‐based oxides and sulfides have been actively investigated due to their low cost and high activity. However, the lower intrinsic conductivity of cobalt oxide and the inferior stability of cobalt sulfides still limit their practical application. Herein, CoO was chosen for a proof‐of‐concept study in which the anion‐doping strategy was used to obtain an excellent catalyst. Sulfur incorporation optimizes the charge‐transfer properties and active sites of sulfur‐doped CoO (S‐CoO) and thus gives rise to improved catalytic activity. Besides sulfur doping, the stable framework of the cobalt oxide was well maintained, and thus high stability of S‐CoO throughout the reaction process was ensured. Nanoflake electrocatalyst: Sulfur‐doped CoO nanoflakes with loosely packed structure were fabricated by reaction of Co3O4 nanosheets with thioacetamide (TAA) which was used as both sulfur source and reducing agent (see figure). Sulfur doping optimizes the charge‐transfer properties and the active sites and thus leads to clearly enhanced catalytic activity in the oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

Abstract Monoclinic clinobisvanite BiVO 4 is one of the most promising photocatalyst due to its stability, low cost, narrow band gap, and suitable valence band maximum (VBM) position. The valence band maximum of about −7.10 eV at vacuum level was observed, which is well below the redox potential of water. However, the conduction band minimum, CBM of about −4.86 eV at vacuum level, which was responsible for its low efficiency. The presence of metal (Bi or V) vacancy changed the charge density and VBM of pristine BiVO 4. Our calculated results revealed that 0.04% of the intrinsic Bi or V defects enhanced p-type conductivity and hence improved photocatalytic activity than O-interstitial in pristine BiVO 4. The optical properties of both pristine and intrinsically defective BiVO 4 were calculated and analyzed with perspective of their photocatalytic properties. Conclusively, the role of Bi or V (metal) vacancies in pristine BiVO 4 was found to be significant than O interstitials in enhancing the photocatalytic properties regarding the solar water splitting. Highlights • The electronic structure of pristine and intrinsically defective BiVO4 was investigated by DFT. • The CBM of BiVO 4 was calculated to be -4.86 eV at vacuum level, which is responsible for its low efficiency. • Bi or V vacancies enhanced p-type conductivity and hence improved photocatalytic activity than O-interstitial in BiVO 4. [ABSTRACT FROM AUTHOR]

The adsorption of sulfur dioxide (SO 2 ) on pristine and modified graphyne (including boron- or nitrogen- doping and introducing a single carbon atom defect) was investigated by density functional theory calculations. The structural, electronic, and magnetic properties of graphyne were changed according to the dopant atom site of doping and vacancy. SO 2 adsorption was obviously affected by modification of graphyne. SO 2 weakly interacted with pristine and nitrogen-doped graphynes. Boron doping at the sp-hybridized carbon site and introducing a single carbon atom vacancy in graphyne brought about a dramatic enhancement in SO 2 adsorption. The strongly chemisorbed SO 2 at these active sites caused deformation of the graphyne structure and electron redistribution, which induced changes in the conductivity and magnetism of graphynes. [ABSTRACT FROM AUTHOR]

Hexagonal turbostratic birnessite, one of the most reactive Mn oxide minerals, is ubiquitous throughout the ocean floor to the surface environment. During its crystallization, birnessite may coexist with Al 3+ , which is the third most abundant crustal element. However, interactions of Al 3+ with birnessite compared to the transition metal (TM) ions have rarely been explored thus far. This study examines the structure and properties of Al 3+ -doped hexagonal turbostratic birnessite to obtain insights into the interaction of metal cations with birnessite-like minerals in natural environments. For Al 3+ -incorporated birnessite, the crystal chemistry of Al 3+ , as well as alteration in the mineral structure, physicochemical properties, and reactivity toward the sorption of Pb 2+ /Zn 2+ is investigated by powder X-ray diffraction, chemical analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Electronic structure calculations based on density functional theory (DFT) are further combined to aid in the experimental interpretation of Al 3+ incorporation. As a comparative system, Fe 3+ -coprecipitated birnessite is also examined. Under the experimental conditions used, only a small amount of Al 3+ is incorporated into birnessite, with a final Al/(Al + Mn) molar ratio of ∼0.07, whereas Fe 3+ is incorporated into birnessite with a final Fe/(Fe + Mn) molar ratio of up to ∼0.21. Irrespective of metal type, the incorporation of a metal cation significantly alters the physicochemical properties of birnessite, such as decrease in the thickness of crystals along the c ∗ axis and coherent scattering domain sizes in the a – b plane and the Mn average oxidation state, increase in the specific surface area and the total amount of hydroxyl groups, in which the contents of hydroxyl groups around vacancies are decreased. The lattice parameters in the a – b plane tend to decrease in Al–incorporated birnessites but first significantly decrease and then increase in Fe-incorporated birnessites. In Fe-incorporated birnessites, ∼32–50% of the total Fe 3+ is located inside the Mn octahedral sheets (INC species). In Al–incorporated birnessites, the edge- and corner-sharing Mn–Mn distances gradually decrease. Density function theory (DFT) computation results support that the dominant species in Al–birnessite is a triple-corner-sharing complex on vacancies. The DFT geometry optimization further demonstrates that the in-plane cell size experimentally observed for these birnessites depends on not only the metal type but also its position in the mineral. The Al- or Fe-birnessites exhibit significantly increased adsorption capacities for Pb 2+ but reduced capacities for Zn 2+ . The metal incorporation effects on the chemical reactivity are discussed with the observed changes in the particle size and available vacancy sites. [ABSTRACT FROM AUTHOR]

In the present paper, density functional theory calculations were carried out on a detailed oxygen reduction reaction (ORR) process catalysed by nitrogen-doped β-graphyne (βGy). Nitrogen-doping can increase the positive charge of the adjacent carbon atom and the graphyne work function, promoting O 2 decomposition. Our calculations revealed that N-doped βGy can efficiently facilitate the ORR process via a four-electron mechanism, regardless of doping position. Additionally, our results revealed that the N doping site was essential for tuning the ORR catalytic activity. N1 doping was shown to more effectively promote the ORR than N2 doping. In addition, our research enhances the current understanding of catalytic activity at the molecular level. [ABSTRACT FROM AUTHOR]

Transition Metal ( TM ) atoms adsorption on γ-graphyne is here studied to unravel the electronic and magnetic properties tuning of this 2D carbon allotrope, with possible repercussions on molecular storage, sensing, and catalytic properties. A thorough density functional theory study, including dispersion, of the structural, energetic, diffusivity, magnetic, and doping properties for all 3 d , 4 d , and 5 d TM adatoms adsorbed on γ-graphyne is provided. Overall, TMs strongly chemisorb on γ-graphyne acetylenic rings, except d 10 group XII TMs which physisorb. Diffusion energy barriers span the 0.5–3.5 eV and adatom height with respect the γ-graphyne sheet seems to be governed by the TM atomic radius. All TMs are found to give n -doped γ-graphyne, where charge transfer decays along d series due to the increasing electronegativity of TMs. Middle TMs infer noticeable magnetism to γ-graphyne, yet magnetism is heavily quenched for early and late TMs. The large adsorption energies close to parent TM bulk cohesive energies, the high diffusion energy barriers, and the coulombic repulsion between positively charged TM adatoms provide a good environment for TMs to disperse over the γ-graphyne. [ABSTRACT FROM AUTHOR]

[Display omitted] • γ-graphdiyne nanoribbons are potential bifunctional CMFCs for ORR and HER after edge functionalization. • sp-N doping can effectively boost the ORR and HER performance of inert γGDyNRs. • Light gradient boosting machine could predict electrocatalytic activities. Graphyne materials have shown promising advantages for fabrication of carbon-based, metal-free catalysts (CMFCs) in the electrocatalytic field. Herein, we report functionalized γ-graphdiyne nanoribbons (γGDyNRs) by edge termination or N doping as potential bifunctional CMFCs for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) via intensive density functional theory (DFT) simulations. It is revealed that sp-N doping (sandwiched by two sp-C) at the inner location and sp2-N doping near the edge can effectively boost the ORR and HER performance of inert γGDyNRs. Our results further demonstrate that sp2-N can play a principal role, especially when at the edge of γGDY; this effect was not addressed in earlier experimental and theoretical work. We also built a machine learning model for predicting bifunctional activities using a light gradient boosting machine. Feature importance analysis shows that the distance between adsorption site and the closest atom to it and the atomic charge of adsorption site are the most important features in determining the activities. Our work not only identifies γGDyNRs as promising alternative catalysts to Pt, but also benefits the rational design of novel CMFCs with high efficiency. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were carried out to study how the position of single-atom doping affects the electronic properties of three graphyne models. We found that the position of the dopant (B, N, or O) plays an important role in tuning the electronic structure of graphynes. For α-graphyne, the electronic structure is significantly different for different positions of B and O doping. For β-graphyne, the electronic structure depends remarkably on the doping position for O doping, but not much for B and N doping, whereas for γ-graphyne, it depends on the position for B and O doping, but not for N doping. [ABSTRACT FROM AUTHOR]