The development of productive catalysts for the oxygen evolution reaction (OER) remains a major challenge requiring significant progress in both mechanism and material design. Conventionally, the ...thermodynamic barrier of lattice oxidation mechanism (LOM) is lower than that of absorbate evolution mechanism (AEM) because the former can overcome certain limitations. However, controlling the OER pathway from the AEM to the LOM by exploiting the intrinsic properties of the catalyst remains challenging. Herein, we incorporated F anions into the oxygen vacancies of spinel ZnCo2O4 and established a link between the electronic structure and the OER catalytic mechanism. Theoretical density calculations revealed that F upshifts the O 2p center and activates the redox capability of lattice O, successfully triggering the LOM pathway. Moreover, the high electronegativity of F anions is favourable for balancing the residual protonation, which can stabilize the structure of the catalyst.
In this work, we successfully filled the lattice oxygen vacancies of ZnCo2O4 with F atom, achieving the activation of lattice oxygen by regulating metal‐oxygen hybridization, and the dominant oxygen evolution reaction mechanism on ZnCo2O4 can transform from adsorbate evolution mechanism to lattice oxygen oxidation mechanism.
The catalytic conversion of alcohols under mild conditions is a great challenge because it is constrained by low selectivity and low activity. Herein, we demonstrate a hollow nanotube Fe2O3/MoO3 ...heterojunction (FeMo‐2) for the photoelectrocatalytic conversion of small‐molecule alcohols. Experimental and theoretical analyses reveal that the optical carrier transfer rate is enhanced by constructing interfacial internal electric fields and Fe‐O‐Mo charge transfer channels. For the formox process, heterojunctions possess superior HCHO‐selective reaction paths and free energy transitions, optimizing the selectivity of HCHO and enhancing the reactivity. FeMo‐2 shows a greatly improved performance compared to single Fe2O3; the photocurrent density of FeMo‐2 reaches 0.66 mA cm−2, which is 3.88 times that of Fe2O3 (0.17 mA cm−2), and the Faraday efficiency of the CH3OH‐to‐HCHO conversion is 95.7 %. This work may deepen our understanding of interfacial charge separation and has potential for the production of HCHO and for conversion reactions of other small‐molecule alcohols at cryogenic temperatures.
A Z‐Scheme Fe2O3/MoO3 hollow nanotube with a CH3OH‐to‐HCHO selectivity of 95.7 % was developed. The thin‐walled hollow structure facilitates a fast transfer of photogenerated carriers and enhances light utilization. The Fe‐O‐Mo charge transfer channel and internal electric field in the Fe2O3/MoO3 interface improve the charge transfer efficiency. PEC experiments and calculations demonstrate that C−H bond breaking is the rate‐determining step.
Constructing rich defect active site structure for material design is still a great challenge. Herein, a simple surface engineering strategy is demonstrated to construct one‐unit‐cell ZnIn2S4 atomic ...layers with the modulated surface energy of S vacancy. Rich surface energy can regulate and control the rich S vacancy, which ensures rich active sites, higher charge density and effective carrier transport. As a result, the ZnIn2S4 atomic layers with rich surface energy affords an obvious enhancement in H2O2 productive rate of 1592.04 µmol g−1 h−1, roughly 14.58 times superior to that with poor surface energy. Moreover, the in situ infrared diffuse reflection spectrum indicates that S vacancy as the oxygen reduction reaction active site is responsible for the critical intermediate *O2− and *OOH, corresponding to two‐electron oxygen reduction reaction. This study provides a valuable insight and guidance for constructing controllably defects to achieve highly efficient H2O2 production.
The ZnIn2S4 atomic layer with rich defect active sits is designed and prepared by a simple hydrothermal method. The relationship between surface energy and defects is investigated by density functional theory calculation and experiment, indicating that the controllable defects can be constructed by tuning surface energy. As the rich active site, S defect played a very important role in charge density and effective carrier transport during the photocatalytic H2O2 production.
By using the more electro‐negative Mn3+ ion to partially replace Co3+ at the octahedral site of spinel ZnCo2O4, i.e., forming ternary Zn–Mn–Co spinel oxide, the electrocatalytic oxygen ...reduction/evolution activity is found to be significantly increased. Considering the physical characterization and theoretical calculations, it demonstrated that the bond competition played a key role in regulating the cobalt valence state and the electrocatalytic activity. The partial replacement of octahedral‐site‐occupied Co3+ by Mn3+ can effectively modulate the adjacent Co–O bond and induce the Jahn–Teller effect, thus changing the originally stable crystal structure and optimizing the binding strength between the active center and reaction intermediates. Certainly, the Mn‐substituted ZnMn1.4Co0.6O4/NCNTs exhibit higher electrocatalytic oxygen reduction reaction (ORR) activity than that of ZnCo2O4/NCNTs and ZnMn2O4/NCNTs, supporting that the Co–O bond covalency determines the ORR activity of spinel ZnCo2O4. This study offers the competition between adjacent Co–O and Mn–O bonds via the BOh–O–BOh edge‐sharing geometry. The ion substitution at octahedral sites by less electronegative cations can be a new and effective way to improve the electrocatalytic performance of cobalt‐based spinel oxides.
The excellent electrocatalytic performance of ZnMn1.4Co0.6O4/NCNTs for oxygen reduction reaction is verified, presenting significant power density and durability in Zn–air batteries. A bond competition mechanism for the octahedral sites of spinel is also proposed. The presence of bond competition between CoO and MnO enables to modulate and optimize the electronic structure of ZnMn1.4Co0.6O4, resulting in the superior electrocatalytic activity.
Nitrogen heterocycles are important structural subunits that occur widely in bioactive natural products, pharmaceuticals, agrochemicals, dyes, cosmetics, and functional materials. Considering the ...importance of these useful compounds in modern science, the synthesis of N‐heterocycles and their derivatives has always been a hot topic in organic synthesis. Recently, arenediazonium salts which can be easily prepared from inexpensive and abundantly available anilines, have been used as versatile nitrogen sources in the field of nitrogen heterocycle synthetic chemistry due to their ready availability, rich reactivity, and diverse transformations. The aim of the present review is to summarize the recent advances in the synthesis of nitrogen heterocycles using arenediazonium salts as nitrogen sources in the past ten years. Hopefully, it can provide practical guidance for the readers who are interested in utilizing arenediazonium salts as building blocks in organic synthesis. For simplicity and clarity, the organization of this review is based on the number of N atoms in the ring of nitrogen heterocycle.
The electronic structure of transition metal complexes can be modulated by replacing partial ion of complexes to obtain tuned intrinsic oxygen reduction reaction (ORR) or oxygen evolution reaction ...(OER) electrocatalytic activity. However, the anion‐modulated transition metal complexes ORR activity of is still unsatisfactory, and the construction of hetero‐anionic structure remains challenging. Herein, an atomic doping strategy is presented to prepare the CuCo2O4‐xSx/NC‐2 (CCSO/NC‐2) as electrocatalysts, the structrual characterization results favorably demonstrate the partial substitution of S atoms for O in CCSO/NC‐2, which shows excellent catalytic performance and durability for OER and ORR in 0.1 m KOH. In addition, the catalyst assembled Zinc–air battery with an open circuit potential of 1.43 V maintains performance after 300 h of cyclic stability. Theoretical calculations and differential charges illustrate that S doping optimizes the reaction kinetics and promotes electron redistribution. The superior performance of CCSO/NC‐2 catalysis is mainly due to its unique S modulation of the electronic structure of the main body. The introduction of S promotes CoO covalency and constructs a fast electron transport channel, thus optimizing the adsorption degree of active site Co to the reaction intermediates.
To investigate the bifunctional performance of hetero‐anionic structure for oxygen electrocatalysis, CuCo2O4‐xSx/NC‐2 catalysts are constructed and afford excellent catalytic performance in oxygen reduction reaction (ORR) or oxygen evolution reaction (OER). The superior performance of the CuCo2O4‐xSx/NC‐2 catalysts is attributed to the unique S modulation of the main body electronic structure, CoS bond provides fast electron transport channel, thus optimizing the adsorption degree of active site Co to the reaction intermediates.
Herein, we highlight redox‐inert Zn2+ in spinel‐type oxide (ZnXNi1−XCo2O4) to synergistically optimize physical pore structure and increase the formation of active species on the catalyst surface. ...The presence of Zn2+ segregation has been identified experimentally and theoretically under oxygen‐evolving condition, the newly formed VZn−O−Co allows more suitable binding interaction between the active center Co and the oxygenated species, resulting in superior ORR performance. Moreover, a liquid flow Zn–air battery is constituted employing the structurally optimized Zn0.4Ni0.6Co2O4 nanoparticles supported on N‐doped carbon nanotube (ZNCO/NCNTs) as an efficient air cathode, which presents remarkable power density (109.1 mW cm−2), high open circuit potential (1.48 V vs. Zn), excellent durability, and high‐rate performance. This finding could elucidate the experimentally observed enhancement in the ORR activity of ZnXNi1−XCo2O4 oxides after the OER test.
The outstanding electrocatalytic performance of Zn0.4Ni0.6Co2O4/NCNTs towards ORR/OER is validated, presenting remarkable rate capability and durability in liquid‐flow Zn–air batteries. A dual‐reinforcement mechanism in the Zn–Ni–Co ternary spinel is also proposed. Zn0.4Ni0.6Co2O4/NCNTs exhibits extreme durability and electrochemically enhanced properties, enabling its application in practical rechargeable zinc–air batteries.
Development of easy‐to‐make, highly active, and stable bifunctional electrocatalysts for water splitting is important for future renewable energy systems. Three‐dimension (3D) porous Ni/Ni8P3 and ...Ni/Ni9S8 electrodes are prepared by sequential treatment of commercial Ni‐foam with acid activation, followed by phosphorization or sulfurization. The resultant materials can act as self‐supported bifunctional electrocatalytic electrodes for direct water splitting with excellent activity toward oxygen evolution reaction and hydrogen evolution reaction in alkaline media. Stable performance can be maintained for at least 24 h, illustrating their versatile and practical nature for clean energy generation. Furthermore, an advanced water electrolyzer through exploiting Ni/Ni8P3 as both anode and cathode is fabricated, which requires a cell voltage of 1.61 V to deliver a 10 mA cm−2 water splitting current density in 1.0 m KOH solution. This performance is significantly better than that of the noble metal benchmark—integrated Ni/IrO2 and Ni/Pt–C electrodes. Therefore, these bifunctional electrodes have significant potential for realistic large‐scale production of hydrogen as a replacement clean fuel to polluting and limited fossil‐fuels.
Three‐dimension nickel‐based electrocatalytic electrodes (Ni/Ni8P3 and Ni/Ni9S8) are developed for application in water splitting. The as‐obtained Ni/Ni8P3 catalytic electrode, particularly exhibiting excellent electrocatalytic activity and stability due to its advanced structure effects, can serve as a highly efficient and stable bifunctional catalyst for overall water splitting.
Herein, we demonstrate the use of heterostructures comprised of Co/β‐Mo2C@N‐CNT hybrids for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline electrolyte. The ...Co can not only create a well‐defined heterointerface with β‐Mo2C but also overcomes the poor OER activity of β‐Mo2C, thus leading to enhanced electrocatalytic activity for HER and OER. DFT calculations further proved that cooperation between the N‐CNTs, Co, and β‐Mo2C results in lower energy barriers of intermediates and thus greatly enhances the HER and OER performance. This study not only provides a simple strategy for the construction of heterostructures with nonprecious metals, but also provides in‐depth insight into the HER and OER mechanism in alkaline solution.
That's evolution: Heterostructures composed of Co/β‐Mo2C@N‐CNTs showed high performance for HER and OER in an alkaline electrolyte. The Co nanoparticles not only create a well‐defined heterointerface with β‐Mo2C, but also overcome the poor OER activity of β‐Mo2C, thus leading to enhanced electrocatalytic activity for HER and OER. DFT calculations showed that cooperation by the N‐CNTs, Co, and β‐Mo2C lowers the energy barriers of intermediates.
Herein, we demonstrate the use of heterostructures comprised of Co/β-Mo
C@N-CNT hybrids for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline electrolyte. The ...Co can not only create a well-defined heterointerface with β-Mo
C but also overcomes the poor OER activity of β-Mo
C, thus leading to enhanced electrocatalytic activity for HER and OER. DFT calculations further proved that cooperation between the N-CNTs, Co, and β-Mo
C results in lower energy barriers of intermediates and thus greatly enhances the HER and OER performance. This study not only provides a simple strategy for the construction of heterostructures with nonprecious metals, but also provides in-depth insight into the HER and OER mechanism in alkaline solution.
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