Boosting the Hydrogen Evolution Reaction Performance of P-Doped PtTe2 Nanocages via Spontaneous Defects Formation

PtTe₂, a member of the noble metal dichalcogenides (NMDs), has aroused great interest in exploring its behavior in the hydrogen evolution reaction (HER) due to the unique type-II topological semimetallic nature. In this work, a simple template-free hydrothermal method to obtain the phosphorus-doped (P-doped) PtTe₂ nanocages with abundant amorphous and crystalline interface (A/C-P-PtTe₂) is developed. Revealed by density functional theory calculations, the atomic Te vacancies can spontaneously form on the basal planes of PtTe₂ by the P doping, which results in the unsaturated Pt atoms exposed as the active sites in the amorphous layer for HER. Owing to the defective structure, the A/C-P-PtTe₂ catalysts have the fast Tafel step determined kinetics in HER, which contributes to an ultralow overpotential (η = 28 mV at 10 mA cm⁻²) and a small Tafel slope of 37 mV dec⁻¹. More importantly, benefiting from the inner stable crystalline P-PtTe₂ nanosheets, limited decay of the performance is observed after chronopotentiometry test. This work reveals the important role of the inherent relationship between structure and activity in PtTe₂ for HER, which may bring another enlightenment for the design of efficient catalysts based on NMDs in the near future.     

Boosting the Electrocatalytic Performance of CoPt Alloy with Enhanced Electron Transfer via Atomically Dispersed Cobalt Sites

Designing electrocatalysts with strong electronic metal-support interaction can effectively regulate the electronic properties of metal active centers, therefore maximizing the catalytic performance. As a proof of concept, heteroatoms doped carbon with CoPt alloy and isolated Co single atoms (CoPt CoSA@NSC) are synthesized using CoPt bimetallic metal-organic framework as the precursor in this work. The existence of CoSA on the carbon substrate leads to more electron transfer between CoPt and the support, and appropriate upward shift of the d band center of the catalysts, which can effectively reduce the reaction barrier of rate determine step and boost the catalytic performance of CoPt alloy. The enhanced catalytic activity and stability of CoPt CoSA@NSC are demonstrated experimentally. Remarkably, the overpotential for hydrogen evolution reaction is only 23 mV at 10 mA cm⁻² and the half-wave potential for oxygen reduction reaction is 0.90 V, both exceeding the commercial Pt/C benchmark. In addition, CoPt CoSA@NSC also exhibits great potential as a cathode electrocatalyst for Zn–air battery, in terms of large open circuit potential of 1.53 V, high power density of 184 mW cm⁻², as well as superior cycling stability. This work provides a novel strategy for regulating the electronic structure and catalytic performance of alloy based electrocatalysts.     

Boosting Chemoselective Hydrogenation of Nitroaromatic via Synergy of Hydrogen Spillover and Preferential Adsorption on Magnetically Recoverable Pt@Fe2O3

It is highly desired but challenging to design high performance catalyst for selective hydrogenation of nitro compounds into amino compounds. Herein, a boosting chemoselective hydrogenation strategy on Pt@Fe₂O₃ is proposed with gradient oxygen vacancy by synergy of hydrogen spillover and preferential adsorption. Experimental and theoretical investigations reveal that the nitro is preferentially adsorbed onto oxygen vacancy of Pt@Fe₂O₃, meanwhile, the H₂ dissociated on Pt nanoparticles and then spillover to approach the nitro for selective hydrogenation (>99% conversion of 4-nitrostyrene, > 99% selectivity of 4-aminostyrene, TOF of 2351 h⁻¹). Moreover, the iron oxide support endows the catalyst magnetic retrievability. This high activity, selectivity, and easy recovery strategy provide a promising avenue for selective hydrogenation catalysis of various nitroaromatic.     

MoS_(2)/Ru异质结构的制备及其电催化析氢反应性能EI北大核心CSCD

二维层状二硫化钼(MoS_(2))是一种非常有前景的替代贵金属铂的电水解制氢催化剂。然而,MoS_(2)电子导电性较差,且在碱性氢析出反应(HER)中对水分子吸附/裂解的活化能垒较高,限制其在碱性电水解的应用。通过一步水热法将MoS_(2)纳米片均匀生长在三维导电碳布(CC)上,以有效提高电极导电性。随后在RuCl_(3)的乙醇溶液中通过溶剂热法可控制备超小Ru纳米颗粒负载MoS_(2)纳米片,形成CC@MoS_(2)/Ru异质结构。Ru的负载能有效促进水吸附/裂解反应,从而和MoS_(2)协同催化HER。采用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等方法对MoS_(2)/Ru进行结构和形貌表征。结果表明:MoS_(2)呈纳米片状交错生长在碳布上,并且超小Ru纳米颗粒(平均粒径2.5 nm)均匀负载在MoS_(2)纳米片上。将CC@MoS_(2)/Ru作为工作电极,石墨棒和Hg/HgO电极分别为对电极和参比电极进行碱性HER测试。在电流密度为-10 mA·cm^(-2)下的过电位仅为71.3 mV,Tafel斜率为104.8 mV·dec^(-1)。通过对其进行计时电位滴定法稳定性测试,发现在恒电流密度-10 mA·cm^(-2)下能够维持至少35 h而没有明显性能衰减。     

Synthesis of CaO2 Nanocrystals and Their Spherical Aggregates with Uniform Sizes for Use as a Biodegradable Bacteriostatic Agent

As a solid precursor to O₂ and hydrogen peroxide (H₂O₂), calcium peroxide (CaO₂) has found widespread use in applications related to disinfection and contaminant degradation. The lack of uniform nanoparticles, however, greatly limits the potential use of this material in other applications related to medicine. Here, a new route to the facile synthesis of CaO₂ nanocrystals and their spherical aggregates with uniform, controllable sizes is reported. The synthesis involves the reaction between CaCl₂ and H₂O₂ to generate CaO₂ primary nanocrystals of 2–15 nm in size in ethanol, followed by their aggregation into uniform, spherical particles with the aid of poly(vinyl pyrrolidone) (PVP). The average diameter of the spherical aggregates can be easily tuned in the range of 15–100 nm by varying the concentrations of CaCl₂ and/or PVP. For the spherical aggregates with a smaller size, they release H₂O₂ and O₂ more quickly when exposed to water, resulting in superior antimicrobial activity. This study not only demonstrates a new route to the synthesis of uniform CaO₂ nanocrystals and their spherical aggregates but also offers a promising bacteriostatic agent with biodegradability.     

Crystalline Ru0.33Se Nanoparticles‐Decorated TiO2 Nanotube Arrays for Enhanced Hydrogen Evolution Reaction

Nowadays, the state‐of‐the‐art electrocatalysts for hydrogen evolution reaction (HER) are platinum group metals. Nonetheless, Pt‐based catalysts show decreased HER activity in alkaline media compared with that in acidic media due to the sluggish dissociation process of H₂O on the surface of Pt. With a cost 1/25 that of Pt, Ru demonstrates a favorable dissociation kinetics of absorbed H₂O. Herein, crystalline Ru_0.33Se nanoparticles are decorated onto TiO₂ nanotube arrays (TNAs) to fabricate Ru_0.33Se @ TNA hybrid for HER. Owing to the large‐specific surface area, Ru_0.33Se nanoparticles are freely distributed and the particle aggregation is eliminated, providing more active sites. The contracted electron transport pathway rendered by TiO₂ nanotubes and the synergistic effect at the interface significantly improve the charge transfer efficiency in the hybrid catalyst. Compared with Ru_0.33Se nanoparticles deposited directly on the Ti foil (Ru_0.33Se/Ti) or carbon cloth (Ru_0.33Se/CC), Ru_0.33Se @ TNA shows an enhanced catalytic activity with an overpotential of 57 mV to afford a current density of 10 mA cm^?2, a Tafel slope of 50.0 mV dec^?1. Furthermore, the hybrid catalyst also exhibits an outstanding catalytic stability. The strategy here opens up a new synthetic avenue to the design of highly efficient hybrid electrocatalysts for hydrogen production.     

Regulating the Electrical Behaviors of 2D Inorganic Nanomaterials for Energy Applications

Recent years have witnessed great developments in inorganic 2D nanomaterials for their unique dimensional confinement and diverse electronic energy bands. Precisely regulating their intrinsic electrical behaviors would bring superior electrical conductivity, rendering 2D nanomaterials ideal candidates for active materials in electrochemical applications when combined with the excellent reaction activity from the inorganic lattice. This Concept focuses on highly conducting inorganic 2D nanomaterials, including intrinsic metallic 2D nanomaterials and artificial highly conductive 2D nanomaterials. The intrinsic metallicity of 2D nanomaterials is derived from their closely packed atomic structures that ensure maximum overlapping of electron orbitals, while artificial highly conductive 2D nanomaterials could be achieved by designed methodologies of surface modification, intralayer ion doping, and lattice strain, in which atomic‐scale structural modulation plays a vital role in realizing conducting behaviors. Benefiting from fast electron transfer, high reaction activity, as well as large surface areas arising from the 2D inorganic lattice, highly conducting 2D nanomaterials open up prospects for enhancing performance in electrochemical catalysis and electrochemical capacitors. Conductive 2D inorganic nanomaterials promise higher efficiency for electrochemical applications of energy conversion and storage.     

Size-Defined Ru Nanoclusters Supported by TiO2 Nanotubes Enable Low-Concentration Nitrate Electroreduction to Ammonia with Suppressed Hydrogen Evolution

Anthropogenic nitrate pollution has an adverse impact on the environment and human health. As part of a sustainable nitrate management strategy, electrochemical denitrification is studied as an innovative strategy for nutrients recycling and recovering. It is, however, challenging to selectively electro-reduce nitrate with low-concentration for ammonia. Herein, the photo-deposition of size-defined Ru nanoclusters (NCs, average size: ≈1.66 nm) on TiO₂ nanotubes (NTs) is demonstrated, which show improved performance for nitrate-to-ammonia electroreduction with a maximum yield rate of ≈600 µg h⁻¹ cm⁻² and a faradic efficiency (FE) of > 90.0% across a broad range of potentials in comparison with electrodeposited Ru nanoparticles (NPs, average size: ≈23.78 nm) on TiO₂ NTs. Experimental and theoretical evidence further suggests the small-size Ru NCs with the intrinsically enhanced selectivity and activity because of the strong metal/substrate interaction and unsaturated coordination state. The findings highlight the size effect on Ru-based catalyst supported on metal oxides, a versatile catalytic model, which allows the regulation of hydrogen adsorption to favor ammonia production over the competing hydrogen evolution reaction.     

原料颗粒度对BaTiO_3陶瓷晶粒大小及PTC效应的影响

通过研究原料颗粒度对 BaTiO_3 PTC 陶瓷晶粒大小的影响,提出并讨论了 BaCO_3和 TiO_2的固相反应模型。在生成 BaTiO_3的固相反应中,首先在 BaCO_3和 TiO_2颗粒之间生成少量 BaTiO_(?),隔离了 BaCO_(?)和 TiO_2的接触,从而阻止反应进行,但离子的扩散可使反应继续进行。在扩散过程中,Ba~(2+)的扩散为主,Ti~(4+)的扩散被抑制而可忽略。根据模型,生成的 BaTiO_3颗粒大小主要由 TiO_2原料的颗粒度决定,与 BaCO_3关系较小。所以 BaTiO_3陶瓷的晶粒大小及其 PTC 效应受 BaCO_3颗粒度的影响较小;在生产中为控制陶瓷晶粒大小,选择 TiO_2原料颗粒度是十分重要的,而 BaCO_3则次之。     

Ru掺杂TiO2和TiO2/SiO2光催化剂的制备及可见光分解水制氢性能研究

采用溶胶-凝胶法制备了系列Ru/TiO2和Ru/TiO2/SiO2可见光活性光催化剂。通过TEM、XPS、XRD、UV-Vis漫反射和电化学对样品进行了表征。发现Ru和Si的存在可以抑制TiO2的相转变和晶粒生长;Ru掺杂使TiO2和TiO2/SiO2对可见光的吸收增强,也提高了光生电子和空穴的分离,因而,提高了催化剂可见光分解水制氢活性。当Ru在TiO2和TiO2/SiO2中的掺杂量分别为0.014%和0.021%(质量分数)时,光催化剂的可见光活性最高,且Ru/TiO2/SiO2活性为Ru/TiO2的5倍。     

Atomic Magnetic Heating Effect Enhanced Hydrogen Evolution Reaction of Gd@MoS2 Single-Atom Catalysts

Atomic heating on single atoms (SAs) to maximize the catalytic efficiency of each active site would be a fascinating solution to break the bottleneck for the performance improvement of single-atom catalysts (SACs) but highly challenging task. Here, based on the Gd@MoS₂ SACs synthesized by a facile laser molecular beam epitaxy method, high-frequency alternating magnetic field (AMF) technology is employed to induce atomic magnetic heating on Gd SAs that is meanwhile demonstrated to be the catalytic active center. Significant improvement in catalytic kinetics under AMF excitation (3.9 mT) is achieved, yielding a remarkable enhancement of hydrogen evolution reaction magnetothermal-current by ≈924%. Through theoretical calculations and spin-related electrochemical experiments, such promotion in catalyst activity can be attributed to spin flip (or canting) in Gd SAs leading to the atomic magnetic heating effect on catalytic active center. Together with the embodied high stability, the implement of AMF to the SAs field is demonstrated in this work, and the precisely atomic magnetic heating on specific SAs offers unprecedented thinking for further improvement of SACs performance in the future.     

Mg2Ni纳米晶储氢材料的机械合金化制备工艺研究

利用机械合金化方法制备了Mg2Ni纳米晶粉末,根据不同球磨参数下样品的X射线衍射结果,分析了球磨过程中相组成、粉末晶粒度等的变化,研究了球磨时间、球磨转速、过程控制剂等工艺条件对粉末晶粒度、机械合金化程度的影响.结果表明:在较高的转速下进行循环变速运行并加入合适的过程控制剂可以使生成Mg2Ni的时间提前,完全合金化的过程缩短,得到的Mg2Ni晶粒度为10nm左右.对Mg2Ni纳米晶粉末进行了初步的贮氢性能研究,结果表明:机械合金化制备的样品在室温下即可吸氢,贮氢性能较之传统材料有较大改善.     

Regulating the Interfacial Electronic Coupling of Fe2N via Orbital Steering for Hydrogen Evolution Catalysis

The capability of manipulating the interfacial electronic coupling is the key to achieving on-demand functionalities of catalysts. Herein, it is demonstrated that the electronic coupling of Fe₂N can be effectively regulated for hydrogen evolution reaction (HER) catalysis by vacancy-mediated orbital steering. Ex situ refined structural analysis reveals that the electronic and coordination states of Fe₂N can be well manipulated by nitrogen vacancies, which impressively exhibit strong correlation with the catalytic activities. Theoretical studies further indicate that the nitrogen vacancy can uniquely steer the orbital orientation of the active sites to tailor the electronic coupling and thus benefit the surface adsorption capability. This work sheds light on the understanding of the catalytic mechanism in real systems and could contribute to revolutionizing the current catalyst design for HER and beyond.     

TiO2薄膜的溶胶-凝胶法制备及其光学特性

采用溶胶-凝胶法在普通载玻片上制备了均匀透明的纳米TiO2薄膜，X射线衍射结果表明薄膜晶粒大小为23．0nm，呈锐钛矿型。通过测量薄膜的紫外可见光透射率和吸光度光谱，对其光学特性和吸收边缘进行了研究，同时计算了薄膜的光学禁带宽度。实验结果表明：随薄膜层数的减少，光吸收带边缘发生了蓝移，光学禁带宽度随之变大，此现象可用量子尺寸效应来解释。     

Improving the Electron Transport Performance of TiO2 Film by Regulating TiCl4 Post-Treatment for High-Efficiency Carbon-Based Perovskite Solar Cells

Titanium oxide (TiO₂) has been widely used as an electron transport layer (ETL) in perovskite solar cells (PSCs). Typically, TiCl₄ post-treatment is indispensable for modifying the surfaces of TiO₂ ETL to improve the electron transport performance. However, it is challenging to produce the preferred anatase phase-dominated TiO₂ by the TiCl₄ post-treatment due to the higher thermodynamic stability of the rutile phase. In this work, a mild continuous pH control strategy for effectively regulating the hydrolysis process of TiCl₄ post-treatment is proposed. As the weak organic base, urea has been demonstrated can maintain a moderate pH decrease during the hydrolysis process of TiCl₄ while keeping the hydrolysis process relatively mild due to the ultra-weak alkalinity. The improved pH environment is beneficial for the formation of anatase TiO₂. Consequently, a uniform anatase-dominated TiO₂ surface layer is formed on the mesoporous TiO₂, resulting in reduced defect density and superior band energy level. The interfacial charge recombination is effectively suppressed, and the charge extraction efficiency is improved simultaneously in the fabricated solar cells. The efficiency of the fabricated carbon electrode-based PSCs (C-PSCs) is improved from 16.63% to 18.08%, which is the highest for C-PSCs based on wide-bandgap perovskites.     

V、Fe对TiMn2储氢合金性能的影响

为改善TiMn2储氢合金的吸放氢性能，采用Fe或Fe、V取代合金中的部分Mn元素进行合金化改性。XRD（X-ray diffraction)分析表明Fe和V的同时引入使合金的相组成由TiMn1-2转变为TiMn1-2和δMnV相共存。P-C-T(Pressure-composition-temperature)测试结果表明，部分Mn被取代后合金吸放氢的滞后效应减小，储氢量提高。根据不同温度下的P-C-T测试结果求出吸氢焓变和熵变值，TiFe0.1Mn1.9和TiFe0.1V0.2Mn1.7合金的吸氢焓变分别为-36.9kJ/molH2和-21.9kJ/molH2。     

炭表面改性对负载型TiO_2/活性炭复合光催化剂性能的影响

采用HNO3、H2O2和O3对商品活性炭进行表面改性处理,考察了改性处理对活性炭表面基团、负载TiO2以及所形成的TiO2/活性炭复合光催化剂性能的影响。利用傅里叶红外光谱(IR)、X射线光电子能谱(XPS)、扫描电镜(SEM)及氮气吸附等手段对材料进行了表征。结果表明,3种改性方法均可有效提高活性炭载体表面的含氧官能团数量,但是对活性炭的比表面积和孔容影响不大;H2O2和O3对活性炭载体改性后可以提高对钛前驱体的吸附性能,HNO3改性有利于TiO2颗粒在活性炭表面的分散。使用改性后的活性炭作为载体制备的TiO2/活性炭光催化降解甲基橙的性能均高于未改性的TiO2/活性炭催化剂,其中以HNO3改性后的TiO2/活性炭活性最高。     

Efficient hydrogen charge into monobenzyltoluene over Ru/MgO catalysts synthesized by thermolysis of Ru3(CO)12 on porous Mg(OH)2 powder

MgO-supported Ru catalysts for H₂ charge into monobenzyltoluene, which is a liquid organic hydrogen carrier, were developed by treating the precipitated Mg(OH)₂ with different methods, namely calcination and hydration, followed by the thermolysis of Ru₃(CO)₁₂-loaded samples under identical conditions. The subsequent investigations revealed that the H₂ storage efficiency depended on the surface atomic ratio of Ru/Mg and basicity of the synthesized catalysts that exhibited similar levels of Ru dispersion. In contrast, the Ru/MgO prepared from commercial Mg(OH)₂ exhibited inferior catalytic performance to the synthesized analogue, owing to its low Ru dispersion. All the presented results suggested that the surface OH-intact Mg(OH)₂ with a fairly high surface area and large pores is required for the synthesis of a highly active Ru/MgO catalyst via thermolysis of Ru₃(CO)₁₂.     

Ultrahigh Performance H2O2 Generation by Single-Atom Fe Catalysts with N/O Bidentate Ligand via Oxalic Acid and Oxygen Molecules Activation

Single-atom catalysts (SACs) for photocatalytic hydrogen peroxide (H₂O₂) generation are researched but it is still challenging to obtain high H₂O₂ yields. Herein, graphite carbon nitride (Fe_SA/CN) confined single Fe atoms with N/O coordination is prepared, and Fe_SA/CN shows high H₂O₂ production via oxalic acid and O₂ activation. Under visible light illumination, the concentration of H₂O₂ generated by Fe_SA/CN can achieve 40.19 mM g⁻¹ h⁻¹, which is 10.44 times higher than that of g-C₃N₄. The enhanced H₂O₂ generation can be attributed to the formation of metal-organic complexes and rapid electron transfer. Moreover, the O₂ activation of photocatalysts is revealed by 3,3′,5,5′-tetramethylbenzidine oxidation. The results display that the O₂ activation capacity of Fe_SA/CN is higher than that of g-C₃N₄, which facilitates the formation of H₂O₂. Finally, density functional theory calculation demonstrates that O₂ is chemically adsorbed on Fe atomic sites. The adsorption energy of O₂ is enhanced from −0.555 to −1.497 eV, and the bond length of O O is extended from 1.235 to 1.292 Å. These results exhibit that the confinement of single Fe atoms can promote O₂ adsorption and activation. Finally, the photocatalytic mechanism is elaborated, which provides a deep understanding for SACs-catalyzed H₂O₂ generation.     

Boosting Cell Performance of LiNi0.8Co0.15Al0.05O2 via Surface Structure Design

Although the high energy density and environmental benignancy of LiNi_0.8Co_0.15Al_0.05O₂ (NCA) holds promise for use as cathode material in Li‐ion batteries, present low rate capabilities, and fast capacity fade limit its broad commercial applications. Here, it is reported that surface modification of NCA cathode (R‐3m) with 5 nm‐thick nanopillar layers and Fm‐3m structures significantly improves electrode structure, morphology, and electrochemical performance. The formation of nanopillar layers increases cycling and working voltage stability of NCA by shielding the host material from hydrofluoric acid and improves structural stability with the electrolyte. The modified NCA cathode exhibits an enhanced 89% capacity retention at a rate of 1 C over that of pristine NCA (75.2%) after 150 cycles and effectively suppresses working voltage fade (a drop of 0.025 V after 300 cycles) during repeated charge–discharge cycles. In addition, the diffusion barrier of Li ions in NCA crystals at 0.80 V is noticeably smaller than that of Li ions in pristine NCA (0.87 eV). These findings demonstrate that this unique surface structure design considerably enhances cycle and rate performance of NCA, which has potential applications in other Ni‐rich layered cathode materials.