Photocatalytic N2 Fixation by Plasmonic Mo-Doped TiO_(2) Semiconductor

Photocatalytic N_(2)xation has attracted substantial attention in recent years,as it represents a green and sustainable devel-opment route toward effciently convert-ing N_(2)to NH_(3)for industrial applications.How to rationally design catalysts in this regard remains a challenge.Here we pro-pose a strategy that uses plasmonic hot electrons in the highly doped TiO_(2)to ac-tivate the inert N_(2)molecules.The synthesized semiconductor catalyst Mo-doped TiO_(2)shows a NH_(3)production effciency as high as 134μmol·g^(-1)·h^(-1)under ambient conditions,which is comparable to that achieved by the conventional plasmonic gold metal.By means of ultra-fast spectroscopy we reveal that the plasmonic hot electrons in the system are responsible for the activation of N_(2)molecules,enabling improvement the catalytic activity of TiO_(2).This work opens a new avenue toward semiconductor plasmon-based photocatalytic N_(2)xation.

Enhanced ambient ammonia photosynthesis by Mo-doped Bi_(5)O_(7)Br nanosheets with light-switchable oxygen vacancies

The fabrication of efficient catalysts to reduce nitrogen(N_(2))to ammonia(NH3)is a significant challenge for artificial N_(2) fixation under mild conditions.In this work,we demonstrated that the simultaneous introduction of oxygen vacancies(OVs)and Mo dopants into Bi_(5)O_(7)Br nanosheets can significantly increase the activity for photocatalytic N_(2) fixation.The 1 mol% Mo-doped Bi_(5)O_(7)Br nanosheets exhibited an optimal NH_(3) generation rate of 122.9μmol g^(-1) h^(-1) and durable stability,which is attributed to their optimized conduction band position,suitable absorption edge,large number of light-switchable OVs,and improved charge carrier separation.This work provides a promising approach to design photocatalysts with light-switchable OVs for N_(2) reduction to NH_(3) under mild conditions,highlighting the wide application scope of nanostructured BiOBr-based photocatalysts as effective N_(2) fixation systems.

Optimizing 3d spin polarization of CoOOH by in situ Mo doping for efficient oxygen evolution reaction

Transition-metal oxyhydroxides are attractive catalysts for oxygen evolution reactions(OERs).Further studies for developing transition-metal oxyhydroxide catalysts and understanding their catalytic mechanisms will benefit their quick transition to the next catalysts.Herein,Mo-doped CoOOH was designed as a high-performance model electrocatalyst with durability for 20 h at 10 mAcm−2.Additionally,it had an overpotential of 260 mV(glassy carbon)or 215 mV(nickel foam),which was 78 mV lower than that of IrO_(2)(338 mV).In situ,Raman spectroscopy revealed the transformation process of CoOOH.Calculations using the density functional theory showed that during OER,doped Mo increased the spin-up density of states and shrank the spin-down bandgap of the 3d orbits in the reconstructed CoOOH under the electrochemical activation process,which simultaneously optimized the adsorption and electron conduction of oxygen-related intermediates on Co sites and lowered the OER overpotentials.Our research provides new insights into the methodical planning of the creation of transition-metal oxyhydroxide OER catalysts.

Electrochemical creation of surface charge transfer channels on photoanodes for efficient solar water splitting

Electrochemical treatment is a popular and efficient method for improving the photoelectrochemical performance of water‐splitting photoelectrodes.In our previous study,the electrochemical activation of Mo‐doped BiVO_(4) electrodes was ascribed to the removal of MoO_(x) segregations,which are considered to be surface recombination centers for photoinduced electrons and holes.However,this proposed mechanism cannot explain why activated Mo‐doped BiVO_(4) electrodes gradually lose their activity when exposed to air.In this study,based on various characterizations,it is suggested that electrochemical treatment not only removes partial MoO_(x) segregations but also initiates the formation of H_(y)MoO_(x) surface defects,which provide charge transfer channels for photogenerated holes.The charge separation of the Mo‐doped BiVO_(4) electrode was significantly enhanced by these charge transfer channels.This study offers a new insight into the electrochemical activation of Mo‐doped BiVO_(4) photoanodes,and the new concept of surface charge transfer channels,a long overlooked factor,will be valuable for the development of other(photo)electrocatalytic systems.

Highly efficient and stable electrocatalyst for hydrogen evolution by molybdenum doped Ni-Co phosphide nanoneedles at high current density

There is an increasingly urgent need to develop cost-effective electrocatalysts with high catalytic activity and stability as alternatives to the traditional Pt/C in catalysts in water electrolysis.In this study,microspheres composed of Mo-doped NiCoP nanoneedles supported on nickel foam were prepared to address this challenge.The results show that the nanoneedles provide sufficient active sites for efficient electron transfer;the small-sized effect and the micro-scale roughness enhance the entry of reactants and the release of hydrogen bubbles;the Mo doping effectively improves the electrocatalytic performance of NiCoP in alkaline media.The catalyst exhibits low hydrogen evolution overpotentials of 38.5 and 217.5 mV at a current density of 10 mA·cm^(-2) and high current density of 500 mA·cm^(-2),respectively,and only 1.978 V is required to achieve a current density of 1000 mA·cm^(-2) for overall water splitting.Density functional theory(DFT)calculations show that the improved hydrogen evolution performance can be explained as a result of the Mo doping,which serves to reduce the interaction between NiCoP and intermediates,optimize the Gibbs free energy of hydrogen adsorption(△G_(*H)),and accelerate the desorption rate of *OH.This study provides a promising solution to the ongoing challenge of designing efficient electrocatalysts for high-current-density hydrogen production.

Two-dimensional bifunctional electrocatalyst(Mo-NiFe-LDH)with multilevel structure for highly efficient overall water splitting

To effectively address energy challenges,it is crucial to explore efficient and stable bifunctional nonprecious metal catalysts.In this study,a Mo-doped nickeliron layered double hydroxide with flower-cluster architecture was successfully prepared by a one-step hydrothermal method,which demonstrated a good water splitting performance.After an appropriate amount of Mo doping,some lattice distortions in the material provided reactive sites for the adsorption and conversion of intermediates,thus optimising the charge distribution of the material.Moreover,the multidimensional void structures formed after doping had a larger specific surface area and accelerated the penetration of the electrolyte,which significantly improved the activity of the catalyst in alkaline media.At 10 mA·cm^(-2),the hydrogen and oxygen evolution overpotentials of Mo-doped nickel-iron double hydroxides(Mo-NiFe LDH/NF-0.2)were 167 and 220 mV,respectively,with an excellent durability up to 24 h.When the Mo-NiFe LDH/NF-0,2 catalyst was used as the cathode and anode of an electrolytic cell,the catalyst achieved a current density of 10 mA·cm^(-2)at an applied voltage of 1.643 V.This study provides a novel approach for designing excellent bifunctional electrocatalysts containing nonprecious metals.

Mo doping provokes two electron reaction in MnO_(2)with ultrahigh capacity for aqueous zinc ion batteries

Rechargeable aqueous zinc ion batteries(AZIBs)based on manganese dioxide(MnO_(2))have received much attention for large-scale energy storage applications,however,their energy density is mainly limited by the one-electron reaction of Mn4+/Mn3+redox.Herein,Mo dopedδ-MnO_(2)(Mo-MnO_(2))is prepared and used as a high-performance cathode for AZIBs,which delivers an⇌⇌ultrahigh specific capacity of 652 mAh·g^(−1)at 0.2 A·g^(−1)based on the two-step two-electron redox reaction of Mn^(4+)Mn^(3+)Mn^(2+).Ex-situ structural analysis and density functional theory calculation reveal that the Mo^(5+)dopant plays an important role in enhancing the electronic conductivity of Mo-MnO_(2)and promoting Jahn–Teller distortion of octahedral[MnO_(6)]in ZnMn_(2)O_(4),which facilitates the second step redox reaction of Mn^(3+)/Mn_(2+).This work provides a novel cathode materials design with multi-electron redox chemistry to achieve high energy density in AZIBs.

Uneven Evolution of Microstructure,Magnetic Properties and Coercivity Mechanism of Mo-Substituted Nd-Ce-Fe-B Alloys

The purpose of this paper is to study the influence of Mo addition on the phase morphologies,microstructures and magnetic properties of the designated alloys.It is found out that the coercivity H_(cj) increases unevenly from 12.2 kOe for(Nd_(0.8)Ce_(0.2))_(13)Fe_(82)B_(5) to the maximum value of 13.3 kOe for(Nd_(0.8)Ce_(0.2))_(13)Fe_(80)B_(5)Mo_(2).The transmission electron microscopy images demonstrate that the grain size decreases with the addition of Mo,which indicates that Mo has grain refinement effect.The correlative analysis gives rise to the conclusion that the coercivity mechanism of the investigated alloys is dominated by pinning type.All in all,the enhancement of the magnetic properties is mainly attributed to the synergistic impact of grain refinement,pinning effects and the micro structural homogenization.The research may shed light on the potential development and application of rare earth-based counterpart magnets.

Abnormal lattice occupation of Mo and related polarons in LiNbO_(3): Hybrid density functional theory investigation

Studies have reported that Mo-doped LiNbO_(3) exhibits excellent photorefractive performance,which may be attributed to the Mo abnormally occupation in Nb sites(MoNb)and the MoNb photorefractive centres.Therefore,we investigate the basic characteristics of Mo-doped LiNbO_(3),including the preferable substitutional sites,doping stability,lattice relaxation,and electronic structures using the spin-polarised density functional theory within semi-local and hybrid functionals.Particularly,the type and properties of the polarons in Mo-doped LiNbO_(3) are studied intensively,and the advantages of MoNb polarons with respect to the MoLi polarons are highlighted.The calculation results of both transfer energies and defect formation energies show that MoNb are preferable to be formed in both stoichiometric and congruent LiNbO_(3),while Mo substitutional Li(MoLi)is consumed in small amounts.MoNb could act as small bound polarons that exhibit fast response to light with respect to the MoLi bound bipolarons.The introduced double-centre by Mo doping is partly responsible for the excellent photorefractive properties of Mo-doped LiNbO_(3).