Single atom doping induced charge-specific distribution of Cu1-TiO_(2)for selective aniline oxidation via a new mechanism

Utilizing single atom sites doping into metal oxides to modulate their intrinsic active sites,achieving precise selectivity control in complex organic reactions,is a highly desirable yet challenging endeavor.Meanwhile,identifying the active site also represents a significant obstacle,primarily due to the intricate electronic environment of single atom site doped metal oxide.Herein,a single atom Cu doped TiO_(2)catalyst(Cu_(1)-TiO_(2))is prepared via a simple“colloid-acid treatment”strategy,which switches aniline oxidation selectivity of TiO_(2)from azoxybenzene to nitrosobenzene,without using additives or changing solvent,while other metal or nonmetal doped TiO_(2)did not possess.Comprehensive mechanistic investigations and DFT calculations unveil that Ti-O active site is responsible for triggering the aniline to form a new PhNOH intermediate,two PhNOH condense to azoxybenzene over TiO_(2)catalyst.As for Cu_(1)-TiO_(2),the charge-specific distribution between the isolated Cu and TiO_(2)generates unique Cu_(1)-O-Ti hybridization structure with nine catalytic active sites,eight of them make PhNOH take place spontaneous dissociation to produce nitrosobenzene.This work not only unveils a new mechanistic pathway featuring the PhNOH intermediate in aniline oxidation for the first time but also presents a novel approach for constructing single-atom doped metal oxides and exploring their intricate active sites.

High-throughput calculation-based rational design of Fe-doped MoS_(2) nanosheets for electrocatalytic p H-universal overall water splitting

Electrocatalytic water splitting is crucial for H2generation via hydrogen evolution reaction(HER)but subject to the sluggish dynamics of oxygen evolution reaction(OER).In this work,single Fe atomdoped MoS_(2)nanosheets(SFe-DMNs)were prepared based on the high-throughput density functional theory(DFT)calculation screening.Due to the synergistic effect between Fe atom and MoS_(2)and optimized intermediate binding energy,the SFe-DMNs could deliver outstanding activity for both HER and OER.When assembled into a two-electrode electrolytic cell,the SFe-DMNs could achieve the current density of 50 mA cm^(-2)at a low cell voltage of 1.55 V under neutral condition.These results not only confirmed the effectiveness of high-throughput screening,but also revealed the excellent activity and thus the potential applications in fuel cells of SFe-DMNs.

A cascade of in situ conversion of bicarbonate to CO_(2) and CO_(2) electroreduction in a flow cell with a Ni-N-S catalyst

Combination of CO_(2) capture using inorganic alkali with subsequently electrochemical conversion of the resultant HCO_(3)^(-)to high-value chemicals is a promising route of low cost and high efficiency.The electrochemical reduction of HCO_(3)^(-)is challenging due to the inaccessible of negatively charged molecular groups to the electrode surface.Herein,we adopt a comprehensive strategy to tackle this challenge,i.e.,cascade of in situ chemical conversion of HCO_(3)^(-)to CO_(2) and CO_(2) electrochemical reduction in a flow cell.With a tailored Ni-N-S single atom catalyst(SACs),where sulfur(S)atoms located in the second shell of Ni center,the CO_(2)electroreduction(CO_(2)ER)to CO is boosted.The experimental results and density functional theory(DFT)calculations reveal that the introduction of S increases the p electron density of N atoms near Ni atom,thereby stabilizing^(*)H over N and boosting the first proton coupled electron transfer process of CO_(2)ER,i.e.,^(*)+e^(-)+^(*)H+^(*)CO_(2)→^(*)COOH.As a result,the obtained catalyst exhibits a high faradaic efficiency(FE_(CO)~98%)and a low overpotential of 425 mV for CO production as well as a superior turnover frequency(TOF)of 47397 h^(-1),outcompeting most of the reported Ni SACs.More importantly,an extremely high FECOof 90%is achieved at 50 mA cm^(-2)in the designed membrane electrode assembly(MEA)cascade electrolyzer fed with liquid bicarbonate.This work not only highlights the significant role of the second coordination on the first coordination shell of the central metal for CO_(2)ER,but also provides an alternative and feasible strategy to realize the electrochemical conversion of HCO_(3)^(-)to high-value chemicals.

Electronic structure and magnetic properties of substitutional transition-metal atoms in GaN nanotubes

The electronic structure and magnetic properties of the transition-metal （TM） atoms （Sc-Zn, Pt and Au） doped zigzag GaN single-walled nanotubes （NTs） are investigated using first-principles spin-polarized density functional calculations. Our results show that the bindings of all TM atoms are stable with the binding energy in the range of 6-16 eV. The Sc- and V-doped GaN NTs exhibit a nonmagnetic behavior. The GaN NTs doped with Ti, Mn, Ni, Cu and Pt are antiferromagnetic. On the contrary, the Cr-, Fe-, Co-, Zn- and Au-doped GaN NTs show the ferromagnetic characteristics. The Mn- and Co- doped GaN NTs induce the largest local moment of 4#B among these TM atoms. The local magnetic moment is dominated by the contribution from the substitutional TM atom and the N atoms bonded with it.

Activating Inert Sites in Cobalt Silicate Hydroxides for Oxygen Evolution through Atomically Doping

Metal silicate hydroxides have been recognized as efficient oxygen evolution reaction(OER)electrocatalysts,yet tailoring of their intrinsic activity remains confused.Herein,Fe had been incorporated into cobalt silicate hydroxide nanosheets and the resulted material achieves a competitive OER catalytic activity.It is found that the doping state obviously affects the electrical transport property.Specifically,highly dispersed Fe atoms(low-concentration Fe doping)trigger slight electron transfer to Co atoms while serried Fe(highconcentration Fe doping)attract vast electrons.By introducing 6 at.%Fe doping,partial relatively inert Co sites are activated by atomically dispersed Fe,bearing an optimal metal 3d electronic occupation and adsorption capacity to oxygen intermediate.The introduced Co-O-Fe unit trigger the p-donation effect and decrease the number of electrons in p*-antibonding orbitals,which enhance the Fe-O covalency and the structural stability.As a result,the sample delivers a low overpotential of 293 mV to achieve a current density of 10 mA cm^(-2).This work clarifies the superiority of atomically dispersed doping state,which is of fundamental interest to the design of doped catalyst.

Monolayer MoS_(2)Fabricated by In Situ Construction of Interlayer Electrostatic Repulsion Enables Ultrafast Ion Transport in Lithium-Ion Batteries

High theoretical capacity and unique layered structures make MoS_(2)a promising lithium-ion battery anode material.However,the anisotropic ion transport in layered structures and the poor intrinsic conductivity of MoS_(2)lead to unacceptable ion transport capability.Here,we propose in-situ construction of interlayer electrostatic repulsion caused by Co^(2+)substituting Mo^(4+)between MoS_(2)layers,which can break the limitation of interlayer van der Waals forces to fabricate monolayer MoS_(2),thus establishing isotropic ion transport paths.Simultaneously,the doped Co atoms change the electronic structure of monolayer MoS_(2),thus improving its intrinsic conductivity.Importantly,the doped Co atoms can be converted into Co nanoparticles to create a space charge region to accelerate ion transport.Hence,the Co-doped monolayer MoS_(2)shows ultrafast lithium ion transport capability in half/full cells.This work presents a novel route for the preparation of monolayer MoS_(2)and demonstrates its potential for application in fast-charging lithium-ion batteries.

MoSe_(2)@N, P-C composites for sodium ion battery

The conversion reaction-based anode materials of sodium ion batteries have relatively high capacity;however,the application of these materials is limited by their structural collapse due to the poor structure stability.In this work,MoSe_(2) nanosheets were synthesized by a solvothermal method.An organic solvent was intercalated into the MoSe_(2) materials to enlarge the interlayer spacing and improve the conductivity of the material.The MoSe_(2) material was coated with an organic pyrolysis carbon and then a uniform carbon layer was formed.The surface carbon hybridization of the nanosheet materials was realized by the introduction of heteroatoms during the sintering process.The as-prepared MoSe_(2)@N,P-C composites showed a superior rate performance as it could maintain the integrity of the morphology and structure under a high current density.The composites had a discharge specific capacity of 302.4 mA·h/g after 100 cycles at 0.5 A/g,and the capacity retention rate was 84.96%.

Au atoms doped in Ti_(3)C_(2)T_(x)MXene:Benefiting recovery of oxygen vacancies towards photocatalytic aerobic oxidation

Photocatalytic aerobic oxidation by using oxygen molecules(O_(2))as green and low-cost oxidants is of great attraction,where the introduction of irradiation has been proved as an efficient strategy to lower reaction temperature as well as promote catalytic performance.Moreover,the oxygen vacancies(OVs)of catalyst are highly active sites to adsorb and activate O_(2)during photocatalytic aerobic oxidation.However,OVs are easily blocked by oxygen atoms from active oxygen species during the catalytic process,leading to the deactivation of catalysis.Herein,a promising catalyst toward photocatalytic aerobic oxidation was successfully developed by recovering the OVs through doping Au atoms into Ti_(3)C_(2)T_(x)MXene(Au/Ti_(3)C_(2)T_(x)).Impressively,Au/Ti_(3)C_(2)T_(x)exhibited remarkable activity under full-spectrum irradiation towards photooxidation of methyl phenyl sulfide(MPS)and methylene blue(MB),attaining a conversion of>90%at room temperature.Moreover,Au/Ti_(3)C_(2)T_(x)also manifested remarkable stability by maintaining>95%initial activity after 10 successive reaction rounds.Further mechanistic studies indicated that the OVs of Au/Ti_(3)C_(2)T_(x)served as the active centers to efficiently adsorb and activate O_(2).More importantly,the doped Au atoms of Au/Ti_(3)C_(2)T_(x)were conducive to the recovery of OVs during photocatalytic process from the results of theoretical and experimental aspects.The recovered OVs of Au/Ti_(3)C_(2)T_(x)continuously and efficiently activated O_(2),directly contributing to the remarkable catalytic activity and stability.

Metal atom doping-induced S-scheme heterojunction boosts the photoelectric response

Carrier migration path and driving forces are two crucial factors for charge separation of heterojunction with efficient photoelectric response from the thermodynamic and kinetic perspectives,respectively.Constructing the S-scheme heterojunction and achieving an efficient migration path for space charge separation have aroused great interest,while a thorough insight into tuning interfacial band bending for S-scheme heterojunction is absent.Herein,we report a class of Zn atom-doped CeO_(2)/g-C_(3)N_(4) heterostructure for achieving a new carrier migration path conversion from inferior type-II to advanced S-scheme.Zn-dependent volcano-type plot for Zn-CeO_(2) is established to tune the Fermi level of CeO_(2).The built-in electric field for carrier flow dynamics strengthens when coupling with g-C_(3)N_(4),which significantly boosts the photoelectric response.Based on the intrinsic enzymelike activity of Zn-CeO_(2),we further demonstrate that the Zn-CeO_(2)/g-C_(3)N_(4) S-scheme heterojunction can be explored for constructing a sensitive nanozymatic photoelectrochemical biosensor for the detection of acetylcholinesterase.

Synthesis of Cu-Doped Layered Transition Metal Oxide Cathode Materials Directly from Metal-Organic Frameworks for Sodium-Ion Batteries

Mn-based layered transition metal oxides are promising cathode materials for sodium-ion batteries(SIBs)because of their high theoretical capacities,abundant raw materials,and environment-friendly advantages.However,they often show insufficient performance due to intrinsic issues including poor structural stability and dissolution of Mn^(3+).Atomic doping is an effective way to address these structural degradation issues.Herein,we reported a new synthesis strategy of a Cu-doped layered cathode by directly calcinating a pure metal-organic framework.Benefiting from the unique structure of MOF with atomic-level Cu doping,a homogeneous Cu-doped layered compound P2-Na_(0.674)Cu_(0.01)Mn_(0.99)O_(2) was obtained.The Cu substitution promotes the crystal structural stability and suppresses the dissolution of Mn,thus preventing the structure degradation of the layered cathode materials.A remarkably enhanced cyclability is realized for the Cu-doped cathode compared with that without Cu doping,with 83.8%capacity retention after 300 cycles at 100 mA·g^(-1).Our findings provide new insights into the design of atomic-level doping layered cathode materials constructed by MOFs for high-performance SIBs.

Surface reconstruction,doping and vacancy engineering to improve the overall water splitting of CoP nanoarrays

Development of a general regulatory strategy for efficient overall water splitting remains a challenging task.Herein,a simple,costfairness,and general fluorination strategy is developed to realize surface reconstruction,heteroatom doping,and vacancies engineering over cobalt phosphide(CoP)for acquiring high-performance bifunctional electrocatalysts.Specifically,the surface of CoP nanoarrays(NAs)becomes rougher,meanwhile F doped into CoP lattice and creating amounts of P vacancies by fluorination,which caused the increase of active sites and regulation of charge distribution,resulting the excellent electrocatalyst performance of F-CoP NAs/copper foam(CF).The optimized F-CoP NAs/CF delivers a lower overpotential of only 35 mV at 10 mA·cm^(−2)for hydrogen evolution reaction(HER)and 231 mV at 50 mA·cm^(−2)for oxygen evolution reaction(OER),and the corresponding overall water splitting requires only 1.48 V cell voltage at 10 mA·cm^(−2),which are superior to the most state-of-theart reported electrocatalysts.This work provides an innovative and feasible strategy to construct efficient electrocatalysts.

A V_(2)O_(3)@N-C cathode material for aqueous zinc-ion batteries with boosted zinc-ion storage performance

The discontinuity of new types of clean energy,such as wind power and solar cells, has promoted the development of large-scale energy storage systems(EES).Rechargeable aqueous zinc-ion batteries(ZIBs) have received extensive attention due to their inherent safety and low cost. At this stage, the performance of ZIBs is still limited by cathode materials. In this work, we have constructed a ZIBs cathode material-V_(2)O_(3)@N–C, through surface coating and N atom doping. The N-doped carbon coating endows V_(2)O_(3)@N–C with excellent structural stability and enhances its electrical conductivity. As a result,V_(2)O_(3)@N–C cathode delivers exceptional reversible of Zn^(2+) intercalation/deintercalation. The fabricated Zn/V_(2)O_(3)@N–C batteries exhibit high capacity of 274.6 mAh·g^(-1) at 5 A·g^(-1) and excellent capacity retention of 94% after 2000 cycles. The reversible intercalation/deintercalation of Zn^(2+) in the V_(2)O_(3)@N–C cathode is proved by ex-situ testing methods. It is believed that this work should inject new vitality into the development of ZIBs cathode.

Ingeniously designed Ni-Mo-S/ZnIn_(2)S_(4) composite for multi-photocatalytic reaction systems

Molybdenum disulfide (MoS_(2)) with low cost, high activity and high earth abundance has been found to be a promising catalyst for the hydrogen evolution reaction (HER), but its catalytic activity is considerably limited due to its inert basal planes. Here, through the combination of theory and experiment, we propose that doping Ni in MoS_(2) as catalyst can make it have excellent catalytic activity in different reaction systems. In the EY/TEOA system, the maximum hydrogen production rate of EY/Ni-Mo-S is 2.72 times higher than that of pure EY, which confirms the strong hydrogen evolution activity of Ni-Mo-S nanosheets as catalysts. In the lactic acid and Na_(2)S/Na_(2)SO_(3) systems, when Ni-Mo-S is used as co-catalyst to compound with ZnIn_(2)S_(4) (termed as Ni-Mo-S/ZnIn_(2)S_(4)), the maximum hydrogen evolution rates in the two systems are 5.28 and 2.33 times higher than those of pure ZnIn_(2)S_(4), respectively. The difference in HER enhancement is because different systems lead to different sources of protons, thus affecting hydrogen evolution activity. Theoretically, we further demonstrate that the Ni-Mo-S nanosheets have a narrower band gap than MoS_(2), which is conducive to the rapid transfer of charge carriers and thus result in multi-photocatalytic reaction systems with excellent activity. The proposed atomic doping strategy provides a simple and promising approach for the design of photocatalysts with high activity and stability in multi-reaction systems.

Carbon-doping-induced negative differential resistance in armchair phosphorene nanoribbons

By using a combined method of density functional theory and non-equilibrium Green＇s function formalism,we investigate the electronic transport properties of carbon-doped armchair phosphorene nanoribbons（APNRs）.The results show that C atom doping can strongly affect the electronic transport properties of the APNR and change it from semiconductor to metal.Meanwhile,obvious negative differential resistance（NDR） behaviors are obtained by tuning the doping position and concentration.In particular,with reducing doping concentration,NDR peak position can enter into m V bias range.These results provide a theoretical support to design the related nanodevice by tuning the doping position and concentration in the APNRs.