Tuning near-gap electronic structure, interface charge transfer and visible light response of hybrid doped graphene and Ag3PO4 composite: Dopant effects

High catalytic activity and abundant active sites in M2C12 monolayer for nitrogen reduction reaction

Developing highly efficient single-atom catalysts (SACs) for the nitrogen reduction reaction (NRR) to ammonia production has garnered significant attention in the scientific community. However, achieving high activity and selectivity remains challenging due to the lack of innate activity in most existing catalysts or insufficient active site density. This study delves into the potential of M2C12 materials (M = Cr, Ir, Mn, Mo, Os, Re, Rh, Ru, W, Fe, Cu, and Ti) with high transition metal coverage as SACs for NRR using first-principles calculations. Among these materials, Os2C12 exhibited superior catalytic activity for NRR, with a low overpotential of 0.39 V and an Os coverage of up to 72.53 wt%. To further boost its catalytic activity, a nonmetal (NM) atom doping (NM = B, N, O, and S) and C vacancy modification were explored in Os2C12. It is found that the introduction of O enables exceptional catalytic activity, selectivity, and stability, with an even lower overpotential of 0.07 V. Incorporating the O atom disrupted the charge balance of its coordinating C atoms, effectively increasing the positive charge density of the Os-d-orbit-related electronic structure. This promoted strong d-π* coupling between Os and N2H, enhancing N2H adsorption and facilitating NRR processes. This comprehensive study provides valuable insights into NRR catalyst design for sustainable ammonia production and offers a reference for exploring alternative materials in other catalytic reactions.

Multiscale CO2 Electrocatalysis to C2+ Products: Reaction Mechanisms, Catalyst Design, and Device Fabrication

Electrosynthesis of value-added chemicals, directly from CO2, could foster achievement of carbon neutral through an alternative electrical approach to the energy-intensive thermochemical industry for carbon utilization. Progress in this area, based on electrogeneration of multicarbon products through CO2 electroreduction, however, lags far behind that for C1 products. Reaction routes are complicated and kinetics are slow with scale up to the high levels required for commercialization, posing significant problems. In this review, we identify and summarize state-of-art progress in multicarbon synthesis with a multiscale perspective and discuss current hurdles to be resolved for multicarbon generation from CO2 reduction including atomistic mechanisms, nanoscale electrocatalysts, microscale electrodes, and macroscale electrolyzers with guidelines for future research. The review ends with a cross-scale perspective that links discrepancies between different approaches with extensions to performance and stability issues that arise from extensions to an industrial environment.

To Investigate the Structural, Electronic, and Optical Characteristics of 2D Hetero-atoms Al, N, B-doped-Graphene Composites For Photocatalytic Applications: A DFT Study.. [DOI: 10.21203/rs.3.rs-3078072/v1]

Two-dimensional (2D) layer structure graphene-doped composites have been confirmed to be an efficient and appropriate material to build effective photo-catalysts with enhanced catalytic efficiency for wastewater and industrial wastage. Graphene exhibits a proficient 2D layer structure, very large conductivity, better-quality electron mobility, and remarkably high surface area with large active sites for the best photocatalytic activity. In the current research structural, electronic, and optical characteristics of 2D Graphene doped-composites are calculated using a first-principles calculation. To use a generalized gradient approximation (GGA) and an ultra-soft pseudopotential (USP), the impact of Aluminium (Al), Nitrogen (N), and Boron (B) on structural, optical, and electronic characteristics of Graphene doped-composites are investigated. By substituting Al, N, and B in Graphene, extra gamma sites are produced into the energy bandgap (Eg). Owing to the difference in ionic radii of Al, N, and B the band gap is found to remarkably increase from 0 to 1.75 eV. The nature of the band gap is found direct. A noteworthy increment is found in Eg as a result of optical conductivity increase of 2.5 to 4.0. Due to the inclusion of Al, N, and B, the energy absorption peaks are increased and shifted to larger energy in the UV-visible spectrum. 2D layer structure doped-Graphene composites have high optical conductivity, refractive index, and energy absorption is an appropriate material for photocatalytic application.

Ag3PO4-based photocatalysts and their application in organic-polluted wastewater treatment

Semiconductor photocatalysis technology has shown great potential in the field of organic pollutant removal, as it can use clean and pollution-free solar energy as driving force. The discovery of silver phosphate (Ag₃PO₄) is a major breakthrough in the field of visible light responsive semiconductor photocatalysis due to its robust capacity to absorb visible light < 520 nm. Furthermore, the holes produced in Ag₃PO₄ under light excitation possess a strong oxidation ability. However, the strong oxidation activity of Ag₃PO₄ is only achieved in the presence of electron sacrifice agents. Otherwise, photocorrosion would greatly reduce the reuse efficiency of Ag₃PO₄. This review thus focuses on the structural characteristics and preparation methods of Ag₃PO₄. Particularly, the recent advances in noble metal deposition, ion doping, and semiconductor coupling, as well as methods of magnetic composite modification for the improvement of catalytic activity and recycling efficiency of Ag₃PO₄-based catalysts, were also discussed, and all of these measures could enhance the catalytic performance of Ag₃PO₄ toward organic pollutants degradation. Additionally, some potential modification methods for Ag₃PO₄ were also proposed. This review thus provides insights into the advantages and disadvantages of the application of Ag₃PO₄ in the field of photocatalysis, clarifies the photocorrosion essence of Ag₃PO₄, and reveals the means to improve photocatalytic activity and stability of Ag₃PO₄. Furthermore, it provides a theoretical and methodological basis for studying Ag₃PO₄-based photocatalyst and also compiles valuable information regarding the photocatalytic treatment of organic polluted wastewater.

Carbon-based metal-free electrocatalysts: from oxygen reduction to multifunctional electrocatalysis

Since the discovery of N-doped carbon nanotubes as the first carbon-based metal-free electrocatalyst (C-MFEC) for oxygen reduction reaction (ORR) in 2009, C-MFECs have shown multifunctional electrocatalytic activities for many reactions beyond ORR, such as oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO₂RR), nitrogen reduction reaction (NRR), and hydrogen peroxide production reaction (H₂O₂PR). Consequently, C-MFECs have attracted a great deal of interest for various applications, including metal-air batteries, water splitting devices, regenerative fuel cells, solar cells, fuel and chemical production, water purification, to mention a few. By altering the electronic configuration and/or modulating their spin angular momentum, both heteroatom(s) doping and structural defects (e.g., atomic vacancy, edge) have been demonstrated to create catalytic active sites in the skeleton of graphitic carbon materials. Although certain C-MFECs have been made to be comparable to or even better than their counterparts based on noble metals, transition metals and/or their hybrids, further research and development are necessary in order to translate C-MFECs for practical applications. In this article, we present a timely and comprehensive, but critical, review on recent advancements in the field of C-MFECs within the past five years or so by discussing various types of electrocatalytic reactions catalyzed by C-MFECs. An emphasis is given to potential applications of C-MFECs for energy conversion and storage. The structure-property relationship for and mechanistic understanding of C-MFECs will also be discussed, along with the current challenges and future perspectives.

Unraveling the relationship between exposed surfaces and the photocatalytic activity of Ag3PO4: an in-depth theoretical investigation

Over the years, the possibility of using solar radiation in photocatalysis or photodegradation processes has attracted remarkable interest from scientists around the world. In such processes, due to its electronic properties, Ag₃PO₄ is one of the most important semiconductors. This work delves into the photocatalytic activity, stability, and reactivity of Ag₃PO₄ surfaces by comparing plane waves with projector augmented wave and localized Gaussian basis set simulations, at the atomic level. The results indicate that the (110) surface, in agreement with previous experimental reports, displays the most suitable characteristics for photocatalytic activity due to its high reactivity, i.e. the presence of a large amount of undercoordinated Ag cations and a high value work function. Beyond the innovative results, this work shows a good synergy between both kinds of DFT approaches.

In situ solid-state fabrication of hybrid AgCl/AgI/AgIO3 with improved UV-to-visible photocatalytic performance

The AgCl/AgI/AgIO₃ composites were synthesized through a one-pot room-temperature in situ solid-state approach with the feature of convenient and eco-friendly. The as-prepared composites exhibit superior photocatalytic performance than pure AgIO₃ for the degradation of methyl orange (MO) under both UV and visible light irradiation. The photodegradation rate toward MO of the AgCl/AgI/AgIO₃ photocatalyst can reach 100% after 12 min irradiation under UV light, or 85.4% after 50 min irradiation under visible light, being significantly higher than AgCl, AgI, AgIO₃ and AgI/AgIO₃. In addition, the AgCl/AgI/AgIO₃ photocatalyst possesses strong photooxidation ability for the degradation of rhodamine B (RhB), methylene blue (MB), phenol, bisphenol A (BPA) and tetracycline hydrochloride under visible light irradiation. The reactive species capture experiments confirmed that the h⁺ and •O²⁻ play an essential role during the photocatalytic process under UV light or visible light irradiation. The enhanced effect may be beneficial from the enhanced light adsorption in full spectrum and increased separation efficiency of photogenerated hole-electron pairs, which can be ascribed to the synergistic effect among AgCl, AgI and AgIO₃ nanoplates in AgCl/AgI/AgIO₃ composites.

Well-defined linear Au n (n = 2-4) chains encapsulated in SWCNTs: a DFT study

One-dimensional (1D) gold nanostructures have been extensively studied due to their potential applications in nanoelectronic devices. Using first-principles calculations, composites consisting of a well-defined linear Au _n (n = 2-4) chain encapsulated in a (9,0) single-walled carbon nanotube (SWCNT) were studied. The translational energy barrier of a single Au atom in a (9,0) SWCNT was found to be 0.03 eV. This low barrier guaranteed the formation of Au _n @ (9,0) SWCNT (n = 1-4) composites. Bond lengths, differential charge densities, and electronic band structures of the composites were studied. The average Au-Au bond lengths in the composites were found to be almost the same as those in the corresponding free-standing linear Au _n . The average bond length increased as the number of Au atoms increased. Charge transfer in all of these composites was slight, although a few valence electrons were transferred from the (9,0) SWCNT and the Au chains to intercalations. The conductivities of the encapsulated linear Au _n (n = 2-4) chains were enhanced to some extent by encapsulating them in the SWCNT.

Dramatically Enhanced Visible Light Response of Monolayer ZrS2 via Non-covalent Modification by Double-Ring Tubular B20 Cluster

The ability to strongly absorb light is central to solar energy conversion. We demonstrate here that the hybrid of monolayer ZrS₂ and double-ring tubular B₂₀ cluster exhibits dramatically enhanced light absorption in the entire visible spectrum. The unique near-gap electronic structure and large built-in potential at the interface will lead to the robust separation of photoexcited charge carriers in the hybrid. Interestingly, some Zr and S atoms, which are catalytically inert in isolated monolayer ZrS₂, turn into catalytic active sites. The dramatically enhanced absorption in the entire visible light makes the ZrS₂/B₂₀ hybrid having great applications in photocatalysis or photodetection.

Non-covalent functionalization of WS2 monolayer with small fullerenes: tuning electronic properties and photoactivity

Atomically thin 2-D transition metal dichalcogenide (TMDCs) heterostructures have attracted growing interest due to their massive potential in solar energy applications due to their visible band gap and very strong light–matter interactions.