Chlorine-anion doping induced multi-factor optimization in perovskites for boosting intrinsic oxygen evolution

The oxygen evolution reaction(OER) plays a crucial role in many electrochemical energy technologies,and creating multiple beneficial factors for OER catalysis is desirable for achieving high catalytic efficiency.Here,we highlight a new halogen-chlorine(Cl)-anion doping strategy to boost the OER activity of perovskite oxides.As a proof-of-concept,proper Cl doping at the oxygen site of LaFeO3(LFO) perovskite can induce multiple favorable characteristics for catalyzing the OER,including rich oxygen vacancies,increased electrical conductivity and enhanced Fe-O covalency.Benefiting from these factors,the LaFeO2.9-δCl0.1(LFOCl) perovskite displays significant intrinsic activity enhancement by a factor of around three relative to its parent LFO.This work uncovers the effect of Cl-anion doping in perovskites on promoting OER performance and paves a new way to design highly efficient electrocatalysts.

Enhanced electrochemical performance of Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3) solid electrolyte by anion doping

Nowadays,the majority of the studies on the substitution are focused on cations(such as Y^(3+),Ti^(4+),P^(5+),etc.)in Li_(1.3)Al_(0.3)Ti_(1.7)(PO_(4))_(3)(LATP),while there are few studies on the substitution of anion O^(2-).In this work,the modified LATP with a series of LiCl(LATPClx,x=0.1,0.2,0.3,0.4)additives is prepared to enhance ionic conductivity.The successful introduction of Cl-makes the length of the c axis decrease from 20.822(2)to 20.792(1)Å,and the bulk conductivity of 2.13×10^(-3) S·cm^(-1) is achieved in LATPCl_(0.3).Moreover,the Al/Ti-O1/Cl1 and Al/Ti-O_(2)/Cl_(2) distance decrease,while the Li1-O_(2)/Cl_(2) distance increases.Lithium ions migrate more easily in the nanochannel of M3-M1-M3.In addition,the LiCl additive increases the relative density and the grain boundary conductivity of LATPClx compounds.Naturally,a higher ionic conductivity of 2.12×10^(–4) S·cm^(-1) and a low activation energy of 0.30 eV are obtained in LATPCl_(0.3).Correspondingly,the symmetric cell exhibits a low overpotential of±50 mV for over 200 h in LATPCl_(0.3).The solid-state Li|LATPCl_(0.3)|NCM811(NCM811=LiNi0.8Co0.1Mn0.1O_(2))battery exhibits high initial capacity 185.1 mAh·g^(-1) with a capacity retention rate of 95.4%after 100 cycles at 0.5 C.This result suggests that LiCl additive is an effective strategy to promote electrochemical properties of LATP solid electrolyte and can be considered for reference to other inorganic solid electrolytes systems.

Metal-to-insulator transition in oxide semimetals by anion doping

Oxide semimetals exhibiting both nontrivial topological characteristics stand as exemplary parent compounds and multiple degrees of freedom,offering a promise for the realization of novel electronic states.In this work,we report the structural and transport phase transition in an oxide semimetal,SrNbO_(3),achieved through effective anion doping.Notably,the resistivity increased by more than three orders of magnitude at room temperature upon nitrogendoping.The extent of electronic modulation in SrNbO_(3)is strongly correlated with misfit strain,underscoring its phase instability to both chemical doping and crystallographic symmetry variations.Using first-principles calculations,we discern that elevating the level of nitrogen doping induces an upward shift in the conductive bands of SrNbO_(3−δ)N_(δ).Consequently,a transition from a metallic state to an insulating state becomes apparent as the nitrogen concentration reaches a threshold of 1/3.This investigation shows effective anion engineering in oxide semimetals,offering pathways for manipulating their physical properties.

Synergistic effect of N- and F-codoping on the structure and photocatalytic performance of TiO_2

Three types of TiO2 nanostructures were synthesized via a facile hydrolysis method at195 °C. Effects of the preparation method and doping with N and F on the crystal structure and photocatalytic performance of TiO2 were investigated. The nanomaterials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller porosimetry, ultraviolet–visible diffuse reflectance spectroscopy and fluorescent emission spectra. Their photo-catalytic activity was examined by the photodegradation of methylene blue in aqueous solution under both ultra-violet and visible light irradiation. The results show that nitrogen and fluorine co-doped anatase TiO2 had the characteristics of a smaller crystalline size, broader light absorption spectrum and lower charge recombination than pure TiO2. Most importantly, more efficient photocatalytic activity under both ultra-violet and visible light was observed. The obtained N–F-TiO2 nanomaterial shows considerable potential for water treatment under sunlight irradiation.

High content anion(S/Se/P)doping assisted by defect engineering with fast charge transfer kinetics for high-performance sodium ion capacitors

The rate-determining process for sodium storage in TiO2 is greatly depending on charge transfer happening in the electrode materials owing to its inferior diffusion coefficient and electronic conductivity.Apart from reducing the diffusion distance of ion/electron,the increasement of ionic/electronic mobility in the crystal lattice is also very important for charge transport.Here,an oxygen vacancy(OV)engineering assisted in high-content anion(S/Se/P)doping strategy to enhance charge transfer kinetics for ultrafast sodium-storage performance is proposed.Theoretical calculations indicate that OV-engineering evokes spontaneous S doping into the TiO2 phase and achieves high dopant concentration to bring about impurity state electron donor and electronic delocalization over S occupied sites,which can largely reduce the migration barrier of Na+.To realize the speculation,high-content anion doped anatase TiO2/C composites(9.82 at%for S in A-TiO2–x-S/C)are elaborately designed.The optimized A-TiO2–x-S/C anode exhibits extraordinarily high-rate capability with 209.6 mAh g-1at 5000 mA g-1.The assembled sodium ion capacitors deliver an ultrahigh energy density of 150.1 Wh kg-1at a power density of 150 W kg-1when applied as anode materials.This work provides a new strategy to realize high content anion doping concentration,and enhances the charge transfer kinetics for TiO2,which delivers an efficient approach for the design of electrode materials with fast kinetic.

低电负性阴离子掺杂调控钴酸锌的电子结构以提高析氧反应活性

电子结构和电导率是析氧反应活性的重要描述符,它们可以通过掺杂来调节.鉴于金属掺杂通常会减少电催化剂的活性位点数量,本工作探究了阴离子掺杂对尖晶石钴酸锌(ZCO)电子结构及其析氧活性的影响.与三价钴为主的ZCO相比,用电负性较低的硫取代氧会提高低自旋态(t_(2g)-^(6)e_(g)^(1))二价钴的占比,其析氧活性要高于低自旋态的三价钴(t_(2g)-^(6)e_(g)^(0)).掺硫钴酸锌(ZCO-S)中钴离子和阴离子之间的电子密度的再分布导致了二价钴的增多,而且钴和硫离子间的强共价作用也会加速电荷迁移.ZCO-S在1.65伏(相对于可逆氢电极)下的比活性比原始ZCO高11倍.相反,掺入具有较高电负性和价态的氟(F)并不能有效地改善电子结构,最终导致材料析氧活性的降低.本工作建立了所掺阴离子的电负性与钴酸锌本征析氧活性之间的联系,并提供了一种通过掺杂不同电负性的阴离子来调控尖晶石氧化物的电子结构的简单有效的方法,这为合理设计高性能尖晶石电催化剂提供了新途径.