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Synthesis of cyclohexanone oxime via the cyclohexanone‐hydroxylamine process is widespread in the caprolactam industry, which is an upstream industry for nylon‐6 production. However, there are two shortcomings in this process, harsh reaction conditions and the potential danger posed by explosive hydroxylamine. In this study, we presented a direct electrosynthesis of cyclohexanone oxime using nitrogen oxides and cyclohexanone, which eliminated the usage of hydroxylamine and demonstrated a green production of caprolactam. With the Fe electrocatalysts, a production rate of 55.9 g h−1 gcat−1 can be achieved in a flow cell with almost 100 % yield of cyclohexanone oxime. The high efficiency was attributed to their ability of accumulating adsorbed hydroxylamine and cyclohexanone. This study provides a theoretical basis for electrocatalyst design for C−N coupling reactions and illuminates the tantalizing possibility to upgrade the caprolactam industry towards safety and sustainability. [ABSTRACT FROM AUTHOR]

Electrocatalytic urea synthesis emerged as the promising alternative of Haber–Bosch process and industrial urea synthetic protocol. Here, we report that a diatomic catalyst with bonded Fe–Ni pairs can significantly improve the efficiency of electrochemical urea synthesis. Compared with isolated diatomic and single-atom catalysts, the bonded Fe–Ni pairs act as the efficient sites for coordinated adsorption and activation of multiple reactants, enhancing the crucial C–N coupling thermodynamically and kinetically. The performance for urea synthesis up to an order of magnitude higher than those of single-atom and isolated diatomic electrocatalysts, a high urea yield rate of 20.2 mmol h−1 g−1 with corresponding Faradaic efficiency of 17.8% has been successfully achieved. A total Faradaic efficiency of about 100% for the formation of value-added urea, CO, and NH3 was realized. This work presents an insight into synergistic catalysis towards sustainable urea synthesis via identifying and tailoring the atomic site configurations. The direct electrocatalytic synthesis of urea via C–N coupling is of great significance. The authors report a diatomic catalyst with bonded Fe–Ni pairs to improve the efficiency of electrochemical urea synthesis from nitrate and CO2. [ABSTRACT FROM AUTHOR]

CO2 electroreduction has gained significant interest. However, fabricating cost‐effective nonprecious‐metal electrocatalysts that can selectively convert CO2 to a specific product remains highly challenging. Herein, Pb‐based materials consisting of Pb0 and PbO confined in ordered mesoporous carbon (OMC) (Pb/PbO@OMC) were constructed for CO2 electroreduction to CO. Interestingly, the activity and selectivity of the Pb/PbO@OMC varied with the molar ratio of Pb0/PbO. The material calcined at 800 °C (Pb/PbO@OMC‐800) with a Pb0/PbO ratio of 0.58 provided the best result with CO as the only carbon‐based product, and the Faradaic efficiency of CO reached 98.3 % at a high current density of 41.3 mA cm−2. Detailed studies indicated that Pb0, PbO, and OMC co‐operated well to enhance the performance of Pb/PbO@OMC‐800, which mainly originated from the good interface between Pb0 and PbO, higher electrochemical active surface area, and faster electron transfer to form the CO2⋅− intermediate. [ABSTRACT FROM AUTHOR]

The exploitation of highly efficient, low-cost, and stable electrocatalysts is a key issue of the broad application of green electrocatalytic reactions and efficient energy devices. Recently, modulating the surface structure of electrocatalysts to improve the catalytic activity has attracted a lot of attention. In particular, defect engineering is an important strategy to modulate the surface electronic structure of electrocatalysts. In this review, an overview of defects in metal, carbon materials, transition metal compounds, and defect-decorated catalysts is presented. The defect species, synthesis methods, characterization, and essential defect catalytic mechanism are introduced. Notably, tuning electronic structure to modulate the intermediates' adsorption energy is highlighted throughout the review. Finally, the design principles for defect electrocatalysts are proposed. The in-depth understanding of the structure–reactivity relationship will provide more profound guidance for the design of defect electrocatalysts and potential application in energy conversion and green synthesis. [ABSTRACT FROM AUTHOR]

Electrocatalysis is dominated by reaction at the solid–liquid–gas interface; surface properties of electrocatalysts determine the electrochemical behavior. The surface charge of active sites on catalysts modulate adsorption and desorption of intermediates. However, there is no direct evidence to bridge surface charge and catalytic activity of active sites. Defects (active sites) were created on a HOPG (highly oriented pyrolytic graphite) surface that broke the intrinsic sp2‐hybridization of graphite by plasma, inducing localization of surface charge onto defective active sites, as shown by scanning ion conductance microscopy (SICM) and Kelvin probe force microscopy (KPFM). An electrochemical test revealed enhanced intrinsic activity by the localized surface charge. DFT calculations confirmed the relationship between surface charge and catalytic activity. This work correlates surface charge and catalytic activity, providing insights into electrocatalytic behavior and guiding the design of advanced electrocatalysts. Highly oriented pyrolytic graphite (HOPG) was employed as a model to analyze the promotion of surface charge for electrocatalytic reactions. Via plasma irradiation, numerous defects are generated, which would induce charge re‐distribution on the surface of HOPG. A direct relationship between surface charge and the electrocatalytic activity is proposed. [ABSTRACT FROM AUTHOR]

Development of highly efficient electrocatalysts with low cost for oxygen reduction reaction (ORR) is crucial for their application in fuel cells and metal‐air batteries. In this work, we report a synthesis of 3D heteroatom‐doped ultrathin carbon nanosheet networks directly starting from solid raw materials. This method represents an operationally simple, general, and sustainable strategy to various ultrathin carbon nanosheet networks. Evaporation of crystalline water and coordination interaction are proposed to be responsible for the formation of the 3D carbon nanosheet networks. The carbon nanosheet networks possess high surface area with micro‐ and macropores, large pore volume, ultrathin nanosheet structure, and effective N/S‐co‐doping. The as‐prepared materials show outstanding electrocatalytic ORR performance with more positive onset potential and half‐wave potential, good methanol tolerance, and excellent stability, compared with those of the porous carbons derived from the ZIF counterpart and commercial Pt/C. This work not only provides highly active ORR electrocatalysts via an operationally simple and green process and also demonstrates a general method to prepare 3D ultrathin carbon nanosheet networks without any additional template and solvent. Operationally simple: 3D highly porous heteroatom‐doped ultrathin carbon nanosheet networks have been synthesized directly starting from solid raw materials without any additional template. The ultrathin structure, hierarchical porosity, and heteroatom‐doping endow as‐prepared ultrathin carbon nanosheet networks with outstanding eletrocatalytic ORR performance. [ABSTRACT FROM AUTHOR]

Utilization of naturally occurring resources to design electrocatalysts for CO2 transformation is environmentally and economically compelling. Herein, we describe the first work on the utilization of naturally occurring phytic acid (PhyA) as the building block to prepare lead phytate (Pb-PhyA) as an electrocatalyst for CO2 electro-reduction to HCOOH. The prepared Pb-PhyA exhibited excellent performance in an ionic liquid based catholyte, and the faradaic efficiency of HCOOH could reach 92.7% at a high current density (30.5 mA cm−2) in a ternary electrolyte consisting of [Bzmim]BF4 (12.8 wt%), H2O (9.9 wt%) and acetonitrile. [ABSTRACT FROM AUTHOR]

Abstract: The number of catalytically reactive sites and their intrinsic electrocatalytic activity strongly affect the performance of electrocatalysts. Recently, there are growing concerns about layered double hydroxides (LDHs) for oxygen evolution reaction (OER). Exfoliating LDHs is an effective method to increase the reactive sites, however, a traditional liquid phase exfoliation method is usually very labor‐intensive and time‐consuming. On the other hand, proper heteroelement doping and edge engineering are helpful to tune the intrinsic activity of reactive sites. In this work, bulk CoFe LDHs are successfully exfoliated into ultrathin CoFe LDHs nanosheets by nitrogen plasma. Meanwhile, nitrogen doping and defects are introduced into exfoliated ultrathin CoFe LDHs nanosheets. The number of reactive sites can be increased efficiently by the formation of ultrathin CoFe LDHs nanosheets, the nitrogen dopant alters the surrounding electronic arrangement of reactive site facilitating the adsorption of OER intermediates, and the electrocatalytic activity of reactive sites can be further tuned efficiently by introducing defects which increase the number of dangling bonds neighboring reactive sites and decrease the coordination number of reactive sites. With these advantages, this electrocatalyst shows excellent OER activity with an ultralow overpotential of 233 mV at 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) with two-dimensional lamellar structures show excellent electrocatalytic properties. However, the catalytic activity of LDHs needs to be further improved as the large lateral size and thickness of the bulk material limit the number of exposed active sites. However, the development of efficient strategies to exfoliate bulk LDHs into stable monolayer LDH nanosheets with more exposed active sites is very challenging. On the other hand, the intrinsic activity of monolayer LDH nanosheets can be tuned by surface engineering. Herein, we have exfoliated bulk CoFe LDHs into ultrathin LDH nanosheets through Ar plasma etching, which also resulted in the formation of multiple vacancies (including O, Co, and Fe vacancies) in the ultrathin 2D nanosheets. Owing to their ultrathin 2D structure, the LDH nanosheets expose a greater number of active sites, and the multiple vacancies significantly improve the intrinsic activity in the oxygen evolution reaction (OER). [ABSTRACT FROM AUTHOR]

Designing highly active, earth-abundant and stable bifunctional electrocatalysts for both the oxygen (OER) and hydrogen (HER) evolution reactions is very crucial to overall water splitting. Herein, we developed nanoparticle-stacked porous Co3FeNx (NSP-Co3FeNx) nanowires as bifunctional electrocatalysts, exhibiting excellent OER and HER activity with a low overpotential of 222 mV at 20 mA cm−2 and 23 mV at 10 mA cm−2, respectively, due to their unique structural advantages with grain boundaries, defects and dislocations. Moreover, the electrocatalysts as bifunctional electrodes show a high performance with 10 mA cm−2 at a cell voltage of 1.539 V. [ABSTRACT FROM AUTHOR]