Ultra‐low single‐atom Pt on g‐C_(3)N_(4)for electrochemical hydrogen peroxide production

Platinum-based materials show excellent electrocatalytic performance and have good potential for use in fuel cells.However,the high cost and scarce reserves have restricted their wide application.Therefore,it is a challenging task to reduce the amount of Pt as well as ensure good catalytic performance.Herein,anchoring of Pt single atoms(0.21 wt‰)with ultra-low content on g-C_(3)N_(4)nanosheets(Pt_(0.21)/CN)has been successfully achieved.The obtained Pt_(0.21)/CN catalyst shows excellent two-electron oxygen reduction(2e-ORR)capability for hydrogen peroxide(H_(2)O_(2)).Compared with CN,its H_(2)O_(2)selectivity increased from 80%to 98%in 0.1M KOH,surpassing those in most of the reported studies.Besides,the H_(2)O_(2)production rate of Pt_(0.21)/CN is 767 mmol gcat^(-1)h-1,which is 11.1 times that of CN.This work may pave the way toward the development of an effective method for the design of noblemetal electrocatalysts with low metal loading and high catalytic activity.

Photocatalyst with Chloroplast-like Structure for Enhancing Hydrogen Evolution Reaction

Photosynthesis with the chloroplast works efficiently because of the envelope structure that serves to carry enzymes and to simultaneously maintain the spatial separation of photosynthesis and cellular respiration.Inspired by the spatially separated architecture,a chloroplast-like structured photocatalyst(PdS@CdS@MoS_(2)),in which the PdS and MoS_(2) function as enzymes in the chloroplast and CdS shell functions as the chloroplast envelope,was developed to improve the photocatalytic H_(2) evolution.In this unique nanoscale bionic structure,the poriferous CdS shell enhances light absorption,generates photoinduced carriers,and separates oxidation and reduction reactions.Meanwhile,PdS and MoS_(2) dual cocatalysts enhance the charge separation efficiency through forming a built-in electric field with CdS.We demonstrate that the separation efficiency of carriers,carrier lifetime,and the yield of H_(2) are both higher than that of CdS nanoparticles,evidencing the feasibility of the chloroplast-like structure in enhancing the photocatalyst activity.This work emphasizes the synergism of the three key processes of the photocatalytic reaction by simulating the chloroplast structure and provides a general synthesis strategy,the synthesis of novel structured for photocatalysts for diverse applications in the energy field.

Oxygen vacancies enriched nickel cobalt based nanoflower cathodes: Mechanism and application of the enhanced energy storage

The rational design of oxygen vacancies and electronic microstructures of electrode materials for energy storage devices still remains a challenge. Herein, we synthesize nickel cobalt-based oxides nanoflower arrays assembled with nanowires grown on Ni foam via the hydrothermal process followed annealing process in air and argon atmospheres respectively. It is found that the annealing atmosphere has a vital influence on the oxygen vacancies and electronic microstructures of resulting NiCo_(2)O_(4) (NCO-Air) and CoNiO_(2) (NCO-Ar) products, which NCO-Ar has more oxygen vacancies and larger specific surface area of 163.48 m^(2)/g. The density functional theory calculation reveals that more oxygen vacancies can provide more electrons to adsorb –OH free anions resulting in superior electrochemical energy storage performance. Therefore, the assembled asymmetric supercapacitor of NCO-Ar//active carbon delivers an excellent energy density of 112.52 Wh/kg at a power density of 558.73 W/kg and the fabricated NCO-Ar//Zn battery presents the specific capacity of 180.20 mAh/g and energy density of 308.14 Wh/kg. The experimental measurement and theoretical calculation not only provide a facile strategy to construct flower-like mesoporous architectures with massive oxygen vacancies, but also demonstrate that NCO-Ar is an ideal electrode material for the next generation of energy storage devices.

Strategies from small-area to scalable fabrication for perovskite solar cells

Recently,perovskite solar cells(PSCs) have flourished,and their power conversion efficiency(PCE) has increased from the initial 3.8% to 25.2% in 2019,which is an unprecedented advance.However,usually high-efficiency and stable PSCs are small-area devices prepared by spin coating.This method is not suitable for the preparation of large-area devices in commercialization.Therefore,there is an urgent need to develop new materials and methods for the scalable fabrication of PSCs.In this review,we first describe the common small-area PSCs preparation methods,understand the nucleation and crystal growth kinetics of perovskite,and analyze the reasons that hinder the development of small-area devices to large-area devices.Next,in order to meet the challenges of PSC’s scalable fabrication,we summarize and analyze four strategies:scaling up precursor solutions,scalable deposition methods for large-area films,scaling up charge-transport layers and back electrodes,developing solar modules.Finally,challenges and prospects are proposed to help researchers prepare high-efficiency large-area PSCs.

NiCo_(2)S_(4)/N microspheres grown on N,S co-doped reduced graphene oxide as an efficient bifunctional electrocatalyst for overall water splitting in alkaline and neutral pH

It is of vital importance to design efficient and low-cost bifunctional catalysts for the electrochemical water splitting under alkaline and neutral pH conditions.In this work,we report an efficient and stable NiCo_(2)S_(4)/N,S co-doped reduced graphene oxide(NCS/NS-rGO)electrocatalyst for water splitting,in which NCS microspheres are composed of one-dimentional(1D)nanorods grown homogeneously on the surface of NS-rGOs).The synergetic effect,abundant active sites,and hybridization of NCS/NS-rGO endow their outstanding electrocatalytic performance for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in both alkaline and neutral conditions.Furthermore,NCS/NS-rGO employed as both anode and cathode in a two-electrode alkaline and neutral system electrolyzers deliver 10 mA/cm^(2) with the low cell voltage of 1.58 V in alkaline and 1.91 V in neutral condition.These results illustrate the rational design of carbon-supported nickel-cobalt based bifunctional materials for practical water splitting over a wide pH range.

A terbium activated multicolour photoluminescent phosphor for luminescent anticounterfeiting

The multicolor photoluminescence(PL) of a Tb3+singly activated NaYGeO4 phosphor is prepared by solid state method.For the first time,it is reported that the PL color of Tb3+in NaYGeO4 phosphor can be tuned from green to blue and,finally,to red by controlling the Tb3+content.The optimal tricolor phosphors are NaYGeO4:0.01 mol% Tb3+(red),NaYGeO4:0.5 mol% Tb3+(blue) and NaYGeO4:5 mol% Tb3+(green),respectively.The PL properties of the NaYGeO4:Tb3+ phosphor were studied in details.The results reveal that the PL color modulations of the NaYGeO4:Tb3+phosphor are essentially due to the cross-relaxation effect of Tb3+,and a possible mechanism on the cross-relaxation is proposed.According to these unique features,a multicolor PL image was fabricated based on the NaYGeO4:Tb3+ phosphor for potential applications in luminescent anticounterfeiting.

Mn,N co-doped Co nanoparticles/porous carbon as air cathode for highly efficient rechargeable Zn-air batteries Hide Author's Information

Oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)are generally catalyzed by precious metals(Pt)and metal oxides(IrO_(2))which still have many shortages including expensive price,poor selectivity and undesirable stability.In this work,we report a Mn0-doped CoN_(x) on N-doped porous carbon(Mn-CoN_(x)/N-PC)composite from carbonizing metal-organic framework(MOF)derivative as the dual-functional catalyst to boost both the ORR and OER performances.Owing to the strong coordination effect between nitrogen and metal elements,the introduction of N can obviously improve the content of Co-N-C active sites for ORR.Meanwhile,the Mn-doping significantly regulates the electronic structure of the Co element and increases the content of Co^(0) which provide efficient OER active sites.Mn-CoN_(x)/N-PC catalyst delivers super dual-functional activity with a half-wave potential of 0.85 V,better than the 20%Pt/C catalyst(0.82 V).When used in Zn-air batteries for testing,Mn-CoN_(x)/N-PC electrocatalyst shows a high power density(145 mW·cm^(−2))and good cycle performance.

Self-luminescence and color-tunable emission in KYb_3F_(10) matrix under different excited sources

A self-luminescence KYb3 F10 material was obtained via a mild hydrothermal method.Its structure,morphology and the corresponding luminescence properties were studied.There is a self-luminesce nce based on the effective recombination of electron and hole on surface defects or electronic centers in KYb3 F10.The pH values have significant impact on crystallinity and self-luminescent intensity of target products.With the introduction of Tb3+and Eu3+into KYb3 F10 matrix,a series of color-tunable emission can be achieved.Simultaneously,Tb3+and Eu3+can also affect the self-luminescent intensity of host slightly.Although there is no obvious energy transfer between host and activators,Tb3+has a distinct sensitive effect on Eu3+ascribed to the energy transfer between Tb3+and Eu3+.In addition,the thermal stability was carefully investigated,which demonstrate the materials can be as a candidate in fluorescent lamps and displays.

从电负性角度选择Cu^(2+)插层:提高水系锌离子电池δ-MnO_(2)正极材料的循环稳定性和倍率性能

离子插层已成为提高δ-MnO_(2)作为水系锌离子电池正极材料的循环稳定性和倍率性能的有效策略,但在实践中离子的选择似乎相当随意.本工作选择Cu^(2+)插层δ-MnO_(2),因为Cu^(2+)和Zn^(2+)具有相似的直径,但Cu^(2+)的电负性(1.359)略高于Zn^(2+)(1.347).因此,Cu^(2+)与MnO_(2)晶格具有更强的相互作用,并且在Zn^(2+)和H+的嵌入/脱出循环期间可保持稳定.Cu掺杂的δ-MnO_(2)(CMO)生成了Cu–O键,其电化学性能得到了较大的改善.在2 A g^(-1)的高电流密度下循环600次后,CMO表现出出色的循环稳定性和100%的容量保持率,而原始δ-MnO_(2)的容量保持率仅为23%.当电流密度从0.2增加到2.0 A g^(-1)时,CMO还表现出优异的倍率性能,容量保持率为72%,远高于原始δ-MnO_(2)(32%).由于Cu^(2+)比Zn^(2+)具有更大的电负性,因此Cu–O键作为稳定的“结构之柱”提高了CMO的循环稳定性.Cu^(2+)掺杂还提高了CMO的电子电导率和离子电导率,降低了H+和Zn^(2+)在电极/电解质界面的电荷转移电阻,从而提高了其倍率性能.这项工作为使用插层策略提高电池电化学性能提供了新的见解.

硫空位修饰的CoNi2S4纳米片用于电化学性能增强的非对称超级电容器

如何安全、高效、简便地制备出具有优异电化学性能的超级电容器电极材料是当前人们十分关注的问题.这些特性通常与电极中的空位和杂质有关.为了研究空位对超级电容器阴极材料性能的影响,我们采用一步水热法制备了具有硫空位的CoNi2S4(r-CoNi2S4)纳米片结构电极材料.利用拉曼光谱、X射线光电子能谱(XPS)等手段对硫空位的形成进行了表征.作为超级电容器的电极,r-CoNi2S4纳米片在电流密度为1 A g-1时具有1918.9 F g-1的高容量、优异的倍率性能(在电流密度为20 A g-1时,相对于1 A g-1的保持率为87.9%)和超常的循环稳定性.与原始的CoNi2S4纳米片电极(1 A g-1时容量为1226 F g-1)相比,r-CoNi2S4电极的性能显著提高.基于r-CoNi2S4正极和活性炭负极的不对称超级电容器具有较高的能量密度.通过点亮三种不同颜色的发光二极管(LED)灯,成功证明了该器件在实际应用中的可行性和巨大潜力.