Doping Sites Research Articles

Insight into the mechanism of nitrogen doping in MXenes with controllable surface chemistry

Nitrogen doping emerges as a potent strategy to enhance the electrochemical attributes of two-dimensional MXene materials, recognized for their utility in energy storage solutions. Although advancements have been made, the specific roles of varied doping sites in modifying electrochemical behavior are not fully delineated. This investigation explores nitrogen-doping mechanisms in MXenes with tailored surface chemistries, utilizing a blend of experimental approaches and density functional theory calculations. The distinct roles of nitrogen dopant sites are explored, and the evolution of the electronic structure and stability of the material before and after nitrogen modifications via the urea hydrothermal method are also investigated. The synthesized N-V2CTx-160 MXene electrodes exhibit favorable surface characteristics for energy storage, achieving impressive capacitance properties with a gravimetric capacitance of 592.9 F/g at 2 mV/s in 1 M H2SO4 electrolyte. This work provides a valuable insight for the development of high-performance MXene electrodes for energy storage applications.

Control Over Nitrogen Dopant Sites in Palladium Metallene for Manipulating Catalytic Activity and Stability in the Oxygen Reduction Reaction

AbstractDoping light elements in Pt‐group metals is an effective approach toward improving their catalytic properties for oxygen reduction reaction (ORR). However, it is challenging to control dopant sites and to establish the correlation between the doping site and the catalytic property. In this paper, this success is demonstrated in controlling N doping sites in Pd metallene to manipulate electrocatalytic properties toward ORR. A Pd metallene sample with N dopant predominantly located at the atomic vacancy site (V‐N‐Pd metallene) exhibits two times higher mass activity in ORR than a Pd metallene sample with N dopant mainly occupied the interstitial site (I‐N‐Pd metallene). However, the I‐N‐Pd metallene shows improved durability than the V‐N‐Pd metallene, with only a 4 mV decay in half‐wave potential after 20 000 cycles. Computational calculation results reveal that the significantly enhanced ORR activity of V‐N‐Pd metallene arises from the atomic vacancy‐doped N, which modulates the electronic structure of Pd metallene to weaken the adsorption energy of intermediate O* species. This work provides guidelines for manipulating catalytic properties by controlling the doping sites of light elements in metal nanostructures.

Exploring electron-transfer pathways in co-pyrolyzed waste-derived carbocatalyst for enhanced peroxydisulfate activation

Heterogeneous catalyst-activated peroxydisulfate (PDS) process has great potential in environmental remediation, but its complex preparation process, high cost, low efficiency, and unclear mechanism hinder its practical application. To overcome these limitations, we introduced an innovative metal-free biochar catalyst (SCSS-NC) derived from waste biomass through co-pyrolysis of shrimp shell and sludge with nitrogen doping. This catalyst improved its performance, achieving 78.45 % degradation of tetracycline, outperforming sludge carbon/PDS systems (46.89 %) and shell carbon/PDS systems (22 %) under the dosage of PDS (0.5 mM) and catalysts (0.5 g/L) within 60 min. This improvement stems from its increased surface area, porosity, and electron transport capabilities. Quenching experiments, delayed contaminant addition experiments, and EPR results demonstrated that the SCSS-NC/PDS system relies on electron transfer, in which activated PDS binds to the catalyst surface, forming a highly reactive composite [SCSS-NC/PDS]* to degrade pollutants. The open-circuit potential and linear scanning voltammetry results confirm the existence of an electron transfer pathway, while the situ Raman spectroscopy results validate the presence of the composite [SCSS-NC/PDS]*. The DFT theoretical calculations provide further confirmation of the conductivity, low energy barrier, and ability to expedite electron transfer exhibited by SCSS-NC. The catalyst performance and characterization before, after, and post-recovery from the reaction pinpoint key active sites: pore adsorption, sp2 graphitic carbon, and graphitic nitrogen doping sites. The SCSS-NC/PDS system demonstrates robust anti-interference capability, suggesting its potential for practical organic wastewater treatment. This study provides novel insights into economical carbocatalyst and their mechanisms for environmental applications.

Vacancy-and doping-mediated electronic and magnetic properties of PtSSe monolayer towards optoelectronic and spintronic applications.

Developing new multifunctional two-dimensional (2D) materials with two or more functions has been one of the main tasks of materials scientists. In this work, defect engineering is explored to functionalize PtSSe monolayer with feature-rich electronic and magnetic properties. Pristine monolayer is a non-magnetic semiconductor 2D material with a band gap of 1.52(2.31) eV obtained from PBE(HSE06)-based calculations. Upon creating single Pt vacancy, the half-metallic property is induced in PtSSe monolayer with a total magnetic moment of 4.00 μ B. Herein, magnetism is originated mainly from S and Se atoms around the defect site. In contrast, single S and Se vacancies preserve the non-magnetic nature. However, the band gap suffers of considerable reduction of the order of 67.11% and 48.68%, respectively. The half-metallicity emerges also upon doping with alkali metals (Li and Na) with total magnetic moment of 1.00 μ B, while alkaline earth impurities (Be and Mg) make new diluted magnetic semiconductor materials from PtSSe monolayer with total magnetic moment of 2.00 μ B. In these cases, magnetic properties are produced mainly by Se atoms closest to the doping site. In addition, doping with P and As atoms at chalcogen sites is also investigated. Except for the half-metallic AsSe system (As doping at Se site), the diluted magnetic semiconductor behavior is obtained in the remaining cases. Spin density results indicate key role of the VA-group impurities in magnetizing PtSSe monolayer. In these cases, total magnetic moments between 0.99 and 1.00 μ B are obtained. Further Bader charge analysis implies the charge loser role of all impurities that transfer charge to the host monolayer. Results presented in this work may suggest promises of the defected and doped Janus PtSSe structures for optoelectronic and spintronic applications.

Adsorption and sensing behavior of Cr-doped WS2 monolayer for hazardous gases in agricultural greenhouses: A DFT study

This study used Density functional theory (DFT) to analyze the adsorption behavior of the Cr-doped WS2 monolayer on five hazardous gases (NH3, SO2, NO, NO2, and CO) in agricultural greenhouses. The optimal stable doped site for the Cr atom was identified, and various adsorption parameters such as adsorption energy, adsorption distance, charge transfer and desorption time were calculated. Results indicated that intrinsic WS2 had limited adsorption capacity for five target gases. Moreover, Cr doped significantly enhanced WS2 monolayer conductivity, shifting NH3, SO2, NO and NO2 adsorption from physisorption to chemisorption with Eads <0.6 eV, while CO remained physisorbed. The conductivity of the five gases underwent significant changes after adsorption on Cr-WS2. Desorption times at four temperatures (298 K, 398 K, 498 K and 598 K) indicate that Cr-WS2 demonstrates ideal gas sensor behavior for NH3 gas. However, the physisorbed and short desorption at room temperature suggested unsuitability for CO detection in practical applications. Conversely, the extended desorption time at 598 K made Cr-WS2 more appropriate as a gas scavenger for SO2, NO and NO2 gases. These findings underscore the potential of Cr-WS2 monolayers as novel gas warning or adsorbent materials, offering crucial applications in detecting and removing hazardous gases in agricultural greenhouses.

Deciphering the Role of Native Defects in Dopant‐Mediated Defect Engineering of Carbon Electrocatalysts

AbstractDoping–dedoping chemistry lays the cornerstone for converting heteroatom dopants into intrinsic defects as the emerging active sites of carbon catalysts, but the defect content is yet hindered by inadequate doping efficiencies. Comprehending crucial factors behind the doping of pristine carbon and their correlation to the catalytic properties of dedoped carbon is thus of high significance. Here, the overlooked impact of native defects in pristine carbon on dopant‐mediated defect engineering of carbon catalysts is explicitly unveiled. Intact fullerene (C60), C60‐derived carbon, and carbon black in distinct pentagon/edge defect states are employed as respective precursors to undergo a nitrogen doping–dedoping treatment. Theoretical and experimental evidence consistently indicates that native pentagons change the preferred N doping site from the edge to the basal plane, leading to a substantially higher doping level. Importantly, in addition to pentagons from the removal of zigzag‐edged pyridinic N, N dopants in in‐plane pentagons are more easily dedoped than those in hexagons, generating even more pentagons in a new pentagon–heptagon–pentagon structure as oxygen reduction active sites. The optimized defect‐rich carbon gives an outstanding half‐wave potential of 0.834 V (0.846 V for Pt/C) via the four‐electron pathway, excellent long‐term durability, and prospective applicability in zinc–air batteries.

Effect of alloying elements on zinc-induced liquid metal embrittlement in steels: A first-principles study

Liquid metal embrittlement (LME) induced by Zn melt in galvanized steels during spot-welding poses a significant challenge to the advancement of the automotive industry. A critical strategy to address this challenge is identifying promising alloying elements capable of mitigating LME. High-throughput first-principles calculations were employed to investigate the segregation behavior of 22 common alloying elements at the Σ5(310) grain boundary of iron and their impact on the grain boundary energy. The results indicate that volume distortion upon doping of the alloying elements predominantly influences their segregation behavior, while the weak bonding between Zn and Fe is responsible for the grain boundary embrittlement. Exploration of solute interaction between Zn and the other alloying element in the Fe grain boundary model reveals that the attraction between metallic doping elements and Zn correlates with both the elastic effects and the magnetic properties of the dopant, while the repulsion between non-metallic elements and Zn is primarily governed by the elastic effects. Separating the grain boundary strengthening energy into mechanical and chemical contributions shows that they correlate linearly with variations in volume of the doping site and changes in bond energy for bonds associated with the doping site at the grain boundary, respectively. Accordingly, the strengthening effect of the doping elements can be estimated by evaluating the induced changes in local volume and bond energies on grain boundaries. Furthermore, potential alloying elements to mitigate the Zn-induced LME are screened and discussed, with B and Mo being the most promising candidates.

Shear Field-Controlled Synthesis of Nitrogen-Doped Carbon Nanochains Forest with High-Density sp3 Defects for Efficient CO2 Electroreduction Reaction.

Defect engineering and nitrogen doping being effective strategies for modulating the surface chemical state of the carbon matrix have been widely explored to promote the catalytic activity in the territory of electrochemical energy storage and conversion devices. However, the controllable synthesis of carbon material with high-density specific defects and high nitrogen doping is still full of challenges. Here, we first synthesize one-dimensional necklace-like nitrogen-doped carbon nanochains (N-CNCs) with abundant defects on carbon fiber paper (CFP) by chemical vapor deposition (CVD) method. The resultant nanostructures are a bunch of interconnected carbon spheres with a hollow structure at the internode and present the complete one-dimensional nanochain configuration. Specifically, the N-CNCs with a corrugated surface possesses high content of sp3 defects (31.2%) and nitrogen (23.6 at %). Combining finite element analysis and experimental results, it reveals that the robust shear field generated by etching gas releasing from thermal decomposition of melamine in situ modulates the CVD process via changing the size and force environment of the metal catalyst droplets for formation of N-CNCs. Benefiting from the high ratio of sp3/sp2 and nitrogen doped on the surface, the N-CNCs@CFP displays a superior electrocatalytic performance for CO2RR, delivering CO Faradaic efficiency of 95.9% and a current density of 23.2 mA cm-2 at -0.86 V vs RHE. This work provides promising synthesis strategy and some inspirations for construction of ultradense and specific defects coupling with nitrogen doping sites into carbon materials to achieve high-efficiency electrocatalysis applications.

Searching for new two-dimensional spintronic materials: Doping-induced magnetism in graphene-like SrS monolayer

In this work, doping approach is explored to induce feature-rich electronic and magnetic properties in graphene-like SrS monolayer and make it prospective spintronic two-dimensional (2D) candidate. For such goal, 3d transition metals (V, Cr, Mn, and Fe) and halogens (F, Cl, Br, and I) are selected as dopants at Sr and S sublattice, respectively. Pristine SrS single layer shows good dynamical and thermal stability. Its indirect-gap semiconductor nature is also asserted with energy gap of 2.87/3.81 eV obtained by PBE/HSE06 functional, generated by the separation in energy between S-3p and Sr-4d orbitals. The magnetic semiconducting with total magnetic moment of 2.00 μB is obtained by creating a single Sr vacancy, meanwhile S single vacancy preserves the non-magnetic nature. The monolayer is significantly magnetized by doping with transition metals, where large total magnetic moments of 3.00, 4.00, and 5.00 μB are obtained for the V-, Cr/Fe-, and Mn-doped SrS monolayer, respectively. In these cases, impurities play a key role on producing magnetic properties and generating the magnetic semiconductor nature. This feature-rich nature is also induced by doping with F atom, where a total magnetic moment of 1.00 μB is obtained that is originated mainly from Sr atoms closest to the doping site. Besides, Cl doping leads to the emergence of the half-metallicity. Importantly, the magnetization becomes significantly weaker according to increase the atomic number of halogen dopants, such that the non-magnetic nature is preserved by doping with I atom. This feature is attributed to the increase of the electronic hybridization. Results presented herein introduce the doped SrS monolayer as promising 2D spintronic materials, exhibiting novel properties that are not found in the pristine counterpart.

Inducing d 0 magnetism in new SrCl2 monolayer towards spintronic applications

Magnetism engineering in two-dimensional (2D) materials has been widely explored to make new spintronic materials. In this work, the doping (with alkali metals at Sr sublattice and with chalcogen atoms at Cl sublattice) method are proposed to induce significant d 0 magnetism in the non-magnetic SrCl2 monolayer. This 2D material is an indirect gap insulator with large band gap of 4.97(6.25) eV as obtained by PBE(HSE06) functional, exhibiting ionic character that is generated by the charge transfer from Sr atom to Cl atoms. The monolayer is significantly magnetized by doping with alkali metals, where a total magnetic moments between 0.90 and 1.00 μ B are obtained. Herein, Cl atoms closest to the doping site make main contribution to the system magnetism. Interestingly, the doped systems exhibit half-metallic behavior that is generated by semiconductor spin-up state and metallic spin-down state. On the other hand, the diluted magnetic semiconductor nature emerges in SrCl2 monolayer as a result of doping with chalcogen atoms. In these cases, total magnetic moment of 1.00 μ B is obtained, where magnetic properties are produced mainly by chalcogen impurities and Cl atoms below them. The electronic and magnetic properties of the doped systems are regulated mainly by the outermost p orbital of Cl and chalcogen atoms, and Sr-4d orbital that form mainly the conduction band. Upon further increasing the doping level of K and O atoms, the half-metallic or magnetic semiconductor natures are preserved. Results presented in this work may introduce new prospective 2D spintronic candidates for spintronic applications, which are derived from a non-magnetic SrCl2 monolayer via doping with d 0 atoms.

Insights into effect of dopant site and dopant concentration on structural, electronic and optical properties of GaNbO[formula omitted] and its implications on visible light photocatalytic behavior: An ab-initio study

First principles electronic structure calculations were performed on pure and chalcogenide doped GaNbO4. Doping with isoelectronic S and Se at the O sites in GaNbO4 shows a dopant site driven anisotropy in the structural properties which affects its electronic, optical and photocatalytic behavior. Band gap reduction in GaNbO4 is more with Se than S and this reduction can be regulated via choice of dopant, dopant site and dopant concentration. GaNbO4 bears an optical absorption profile similarity with anatase TiO2 (a-TiO2). Besides directional anisotropy, dopant induced absorption in the visible regime displays a site driven anisotropy, which, has implications on the onset of absorption and absorption peak heights. The visible region absorption peaks can be modulated with changes in the dopant concentration. Se dopant at a lower concentration gives a broader visible regime absorption peak of similar peak height as of a higher concentration S dopant. Undoped GaNbO4 has valence band maxima and conduction band minima at similar energies as a-TiO2 and these band placements can be altered through choice of dopant element, dopant site and dopant concentration to tune the visible light photocatalytic performance. Our study shows that doped GaNbO4 has a stronger visible range absorption than doped a-TiO2.

Machine-Learning-Driven High-Throughput Screening for High-Energy Density and Stable NASICON Cathodes.

The Na super ionic conductor (NASICON), which has outstanding structural stability and a high operating voltage, is an appealing material for overcoming the limits of low specific energy and larger volume distortion of sodium-ion batteries. In this study, to discover ideal NASICON cathode materials, a screening platform based on density functional theory (DFT) calculations and machine learning (ML) is developed. A training database was generated utilizing the previous 124 545 electrode databases, and a test set of 3126 potential NASICON structures [NaxMyM'1-y(PO4)3] with 27 dopants at the metal site and 6 dopants at the polyanion central site was constructed. The developed ML surrogate model identifies 796 materials that satisfy the following criteria: formation energy of <0.0 eV/atom, energy above hull of ≤0.025 eV/atom, volume change of ≤4%, and theoretical capacity of ≥50 mAh/g. The thermodynamically stable configurations of doped NASICON structures were then selected using machine learning interatomic potential (MLIP), enabling rapid consideration of various dopant site configurations. DFT calculations are followed on 796 screened materials to obtain energy density, average voltage, and volume change. Finally, 50 candidates with an average voltage of ≥3.5 V are identified. The suggested platform accelerates the exploration for optimal NASICON materials by narrowing the focus on materials with desired properties, saving considerable resources.

Synchronously integration of carbon-quantum-dot and Cu, Mo dual-metal doped in Ni3S2@Ni foam toward robust and stable electrocatalytic hydrogen generation

In the pursuit of advancing the production of H2 through hydrogen-evolution reaction (HER), the demand for the elaborate design of cost-effective and robust durability electrocatalysts has gained momentum, especially replacement of noble-metal counterparts like Pt. Herein, we introduce a facile one-pot hydrothermal approach to synthesize nickel foam-supported Ni3S2 nanosheet arrays, which integrate with carbon-quantum-dot (CQDs) and Cu, Mo dual-metal doped. With the introduction of CQDs and Cu, Mo dual-metal doped site, the optimal CQDs-Cu-Mo-Ni3S2@NF exhibits superior HER catalytic activity with a low overpotential of 125 mV at 10 mA·cm−2 and strong durability for 30 h in alkaline medium. The exceptional electrocatalytic performance is ascribed to the synergistic effect of CQDs and Cu, Mo dual-metal site. This synergy encompasses optimization of water molecule adsorption/desorption energetics, elevated electrical conductivity, weakening of the strong S–H bond interaction on the Ni3S2 surface, and providing ample active centers. Furthermore, an in-depth understanding of the electronic structure and adsorption energy during the HER process is probed by density functional theory (DFT) analysis. Our work provides a quintessential paradigm for the rational design of multi-component electrocatalysts for water splitting.

Codoping Eu3+ with Sc3+ and La3+ in CaSnO3 for possible site selective doping: Is size selection in site selective doping really effective?

Local site of dopant in host lattice with multiple cationic sites is very important from light emission perspective in dictating its various photophysical features. The same is very important particularly in perovskites which is considered a very important invention for optoelectronic applications. Here in this work we have investigated the local site of dopant and time resolved photoluminescence in CaSnO3:Eu red emitting phosphor on co-doping La3+ and Sc3+ based on their size proximity to A and B-site respectively. EXAFS spectroscopy suggested increase in coordination number of Eu3+ from 6 to 8 and formation of Sn and Ca vacancies as charge compensating defects (CCDs) in La3+ and Sc3+ co-doped samples respectively. Co-doping with either La3+or Sc3+ is directing more fraction of Eu3+ to asymmetric 8-coordinated Ca2+ site compared to relatively symmetric 6-coordinated Sn4+ site. Sc3+ codoping direct more Eu3+ to Ca2+ site but with less distortions in the lattice owing to smaller size of Eu3+ than Ca2+ and higher size of Sc3+ than Sn4+. In case of La3+ co-doping, directing Eu3+ to Sn4+ site is not so effective owing to larger size of Eu3+ than Sn4+ as well as La3+ than Ca2+ and both cause significant distortions in the lattice. PL intensity also improved in the co-doped samples with Sc3+ co-doping emerging victorious over La3+ due to better charge compensation encountered in the former. Excitation dependent PL suggested Eu3+ at Ca2+ sites is preferentially excited under 250 nm and Eu3+ at Sn4+ symmetric site is preferentially excited under 300 nm.

Demystifying the Influence of Precursor Structure on S‐Doped Hard Carbon Anode: Taking Glucose, Carbon Dots, and Carbon Fibers as Examples

AbstractHeteroatom doping is a promising strategy for adjusting the microstructure of hard carbon (HC) to promote its electrochemical sodium storage performance. However, clarifying the doping sites of heteroatoms and effectively regulating their doping levels remain serious challenges. Herein, this work reveals the impact of three distinct structural precursors on S‐doped hard carbon: namely glucose (small organic molecule), carbon dots (CDs, intermediate state between organic and inorganic), and graphitized carbon fibers (inorganic carbon materials). It is demonstrated that the S‐doped HC derived from CDs possesses a more significant number of C─S bonds within its carbon framework, which is attributed to the preferential bonding between sulfur and short polymeric chains abundant in unsaturated functional groups. And these chains cluster prominently on the surface of CDs, enhancing the affinity of sulfur. Furthermore, as a prominent feature of CDs, the extremely small size inherently distinguishes them from other precursors, enabling them to serve as fundamental units for constructing various carbon microstructures, such as three‐dimensional (3D) structure. In summary, this study explores the influence of different precursor structures on heteroatom doping, with CDs identified as the most useful precursor.

Exploring the impact of S-doped Fe-N-C materials on the ORR mechanism within a constant potential solvation model

The widespread application of S doping in Fe-N-C materials aims to enhance the catalytic activity for oxygen reduction reactions (ORR). However, the current doping strategies are primarily centered on the first coordination layer encompassing Fe atoms. Consequently, this study employs first-principles calculations to compute the formation and binding energies of FeN4 doped with S atom. It further delves into the influence of diverse doping sites on catalyst stability and meticulously analyzes the configurations and corresponding ORR activities of four catalysts, namely FeN4S-N (Number=0∼3), utilizing a constant-potential implicit solvent model to simulate authentic electrocatalytic environments. The findings reveal that under vacuum conditions, FeN4S1 exhibits the utmost ORR activity, boasting a potential of 0.53 V. Conversely, within the constant-potential implicit solvation model, FeN4S2 emerges as the catalyst with the highest ORR activity, achieving a potential of 0.39 V. Therefore, calculations leveraging the constant-potential solvation model offer more realistic insights into catalyst design, thereby guiding the development of superior catalysts.

Boosting tetracycline degradation of BaTiO3-based piezo-catalysts via modulating phase boundary and band structure

Piezoelectric catalysis, which converts mechanical energy into chemical activity, has important applications in environmental remediation. However, the piezo-catalytic activity of various piezoelectric materials is limited by the weak piezoelectricity as well as the mismatched band-gap, leading to inefficient electron-hole pair generation and difficult carrier migration. Here, a simple strategy combining phase boundary and energy band structure modulation was innovatively proposed to enhance the piezo-catalytic activity of BaTiO3 ferroelectric by Ce ions selecting different doping sites. Thanks to the coexistence of tetragonal (P4mm) and orthorhombic (Amm2) phases effectively flattened the Gibbs free-energy and thus enhanced the piezoelectric activity, as well as suitable energy bandwidth facilitating the carrier migration were realized in the B-sites doped Ba(Ti0.95Ce0.05)O3. The degradation rate constant k of tetracycline (TC) was high to 30.56 × 10-3 min−1, which was 2.03 times higher than that of pure BaTiO3 and superior to most representative lead-free perovskite piezoelectric materials. Theoretical calculations validated that the charge density and high O2 and OH– adsorption energy on the Ba(Ti0.95Ce0.05)O3 surface promoted more efficient •O2– and •OH radicals conversion and bettered response to piezo-catalytic reaction. This work is important to design high-performance piezo-catalysts by synergistic regulation of phase boundary and energy band structure in perovskite materials for long-term antibiotic tetracycline removal.

Facile construction of a cobalt-incorporated N-doped porous carbon from biomass for highly efficient removal of tetracycline

The performance of heterogeneous carbon-based catalysts in advanced oxidation processes (AOPs) significantly relies on their structure and surface active sites. Herein, the cobalt-incorporated N-doped porous carbon (Co-NC) was successfully prepared from tannin by utilizing its strong ability to coordinate with metal ions. The characterization results revealed that Co-NC-900 possessed a porous structure with abundant mesopores, a relatively large BET surface area (187.16 m2/g), multivalent cobalt species (Co0, Co2+, Co3+) and optimal surface nitrogen sites. As a result, Co-NC-900 demonstrated efficient PMS activation, resulting in a 97.4% removal of tetracycline (TC), along with a rate constant (kobs) of 0.131 min−1 and TOC removal efficiency of 55.3% within 30 min. The analysis of radical inhibition and EPR results revealed that TC degradation was attributed to both non-radical (1O2) and radical (•OH and SO4•-) pathways. In addition, the outperformance of Co-NC-900 compared to Co-C-900 and NC-900 highlights the essential contributions of both Co and N in PMS activation. Mechanism studies have revealed that the presence of multivalent Co species promotes the Co-based redox cycle. This, in association with the enhanced electron transfer efficiency facilitated by N doping sites, accelerates the rapid generation of reactive oxygen species (ROSs). This work provides a straightforward strategy to fabricate transition metal-incorporated N-doped porous carbon catalysts from eco-friendly biomass, contributing to the effective treatment of organic contaminant.

Advancing bandgap tuning: Novel nitrogen doping in KLaTiO4 with uncompromised crystallinity

KLaTiO4 is a promising photocatalyst, producing 9.54(11) µmol of hydrogen gas per hour. Its high bandgap, of 4.09 eV, makes it unsuitable for direct photocatalysis under sunlight irradiation. In this study two novel methods of doping KLaTiO4 with nitrogen were studied, in an attempt to reduce the bandgap of KLaTiO4 without inducing structural degradation of the photocatalyst, which adversely affects the hydrogen evolution rate. The first method involves post-synthesis calcination of KLaTiO4 with urea under a nitrogen atmosphere, and the second method attempts to introduce nitrogen during synthesis, by replacing TiO2 with TiN as a starting reagent. The samples were structurally characterised using powder X-ray diffraction and their bandgap and photocatalytic performance determined by Tauc plot and hydrogen evolution testing. Density Function Theory calculations have been used to probe the likely site of nitrogen doping.

Atomic position and the chemical state of an active Sn dopant for Sn-doped β-Ga2O3(001)

We investigated the atomic position and the chemical state of an active Sn dopant for Sn-doped β-Ga2O3(001) using x-ray absorption near the edge structure (XANES) and hard x-ray photoelectron spectroscopy. We found that the Sn dopant had only one chemical state, which was a Sn4+ oxidation state. The bond length around the Sn dopant atom became longer due to the relaxation effect after the Sn dopant insertion. Comparison of the experimental and simulated XANES spectra showed that the octahedral Ga substitutional site in the β-Ga2O3(001) is an active Sn dopant site.