Metal-Free and Noble Metal-Free Heteroatom-Doped Nanostructured Carbons as Prospective Sustainable Electrocatalysts

Reduction-Specified Coupling Reactions of Nitroarenes by Heterogeneous Cobalt Catalysis

The in-depth study on reduction-specified coupling reactions of the nitroarenes by heterogeneous cobalt catalysis opens a door for diversified syntheses of functional N-containing molecules. Guided by the structure-function relationship of heterogeneous materials, rational design of nano-catalysts can effectively regulate the routes of organic reactions. Precise transformation of the intermediates generated during the nitroarene reduction with a suitable nano-catalyst is a promising way to develop new tandem reactions, and to synthesize structurally novel compounds that are of difficult access with the conventional approaches.

Electrochemical hydrogenation and oxidation of organic species involving water

Fossil fuel-driven thermochemical hydrogenation and oxidation using high-pressure H2 and O2 are still popular but energy-intensive CO2-emitting processes. At present, developing renewable energy-powered electrochemical technologies, especially those using clean, safe and easy-to-handle reducing agents and oxidants for organic hydrogenation and oxidation reactions, is urgently needed. Water is an ideal carrier of hydrogen and oxygen. Electrochemistry provides a powerful route to drive water splitting under ambient conditions. Thus, electrochemical hydrogenation and oxidation transformations involving water as the hydrogen source and oxidant, respectively, have been developed to be mild and efficient tools to synthesize organic hydrogenated and oxidized products. In this Review, we highlight the advances in water-participating electrochemical hydrogenation and oxidation reactions of representative organic molecules. Typical electrode materials, performance metrics and key characterization techniques are firstly introduced. General electrocatalyst design principles and controlling the microenvironment for promoting hydrogenation and oxygenation reactions involving water are summarized. Furthermore, paired hydrogenation and oxidation reactions are briefly introduced before finally discussing the challenges and future opportunities of this research field.

The synthesis of copper-modified biochar from Elsholtzia Harchowensis and its electrochemical activity towards the reduction of carbon dioxide

Phytoremediation techniques have been widely used in the treatment of heavy metal contaminated soils in recent years, but there is no effective post-treatment method for plant tissues containing heavy metals after remediation. Elsholtzia Harchowensis is a copper hyperaccumulator, commonly distributed in copper mining areas and often used for soil remediation of mine tailings. Moreover, copper-based catalysts are widely used in electrocatalytic reduction of carbon dioxide, which aims to convert carbon dioxide into useful fuels or chemicals. In this study, copper-modified biochar was prepared from Elsholtzia Harchowensis. Its specific surface area can reach as high as 1202.9 m2/g, with a certain porous structure and even distribution of copper on the amorphous carbon. Various products (such as carbon monoxide, methane, ethanol, and formic acid) could be obtained from the electrolytic reduction of carbon dioxide by using the as-prepared catalyst. Instantaneous current density of up to 15.3 mA/cm2 were achieved in 1.0 M KHCO3 solution at a potential of -0.82 V (vs. RHE). Electrolysis at a potential of -0.32 V (vs. RHE) for 8 h resulted in a stable current of about 0.25 mA/cm2, and the Faraday efficiency (FE) of carbon monoxide can reach as high as 74.6%. In addition, electrolysis at a potential of -0.52 V (vs. RHE) for 8 h led to a stable current of about 2.2 mA/cm2 and a FE of 8.7% for the C2 product. The rich variety of elements in plants leads to catalysts with complex structural and elemental characteristics as well, which facilitates the electrolytic reduction of carbon dioxide with a variety of useful products.

Designed Nanomaterials for Electrocatalytic Organic Hydrogenation Using Water as the Hydrogen Source

ConspectusThe hydrogenation reaction is one of the most frequently used transformations in organic synthesis. Electrocatalytic hydrogenation by using water (H₂O) as the hydrogen source offers an efficient and sustainable approach to synthesize hydrogenated products under ambient conditions. Such a technique can avoid the use of high-pressure and flammable hydrogen gas or other toxic/expensive hydrogen donors, which usually cause environmental, safety, and cost concerns. Interestingly, utilizing easily available heavy water (D₂O) for deuterated syntheses is also attractive due to the widespread applications of deuterated molecules in organic synthesis and the pharmaceutical industry. Despite impressive achievements, electrode selection mainly relies on trial-and-error modes, and how electrodes dictate reaction outcomes remains elusive. Therefore, the rational design of nanostructured electrodes for driving the electrocatalytic hydrogenation of a series of organics via H₂O electrolysis is developed.In this Account, we review recent advances in the electrocatalytic hydrogenation of different types of organic functional groups, including C≡C, C≡N, C═C, C═O, and C-Br/I bonds, -NO₂, and N-heterocycles, with H₂O over nanostructured cathodes. First, the general reaction steps (reactant/intermediate adsorption, active atomic hydrogen (H*) formation, surface hydrogenation reaction, product desorption) are analyzed, and key factors are proposed to optimize hydrogenation performance (e.g., selectivity, activity, Faradaic efficiency (FE), reaction rate, and productivity) and inhibit side reactions. Then, ex situ and in situ spectroscopic tools to study key intermediates and interpret mechanisms are introduced. Third, based on the knowledge of key reaction steps and mechanisms, we introduce catalyst design principles in detail on how to optimize the adoption of reactants and key intermediates, promote the formation of H* from water electrolysis, inhibit hydrogen evolution and side reactions, and improve the selectivity, reaction rate, FEs, and space-time productivity of products. We then introduce some typical examples. (i) P- and S-modified Pd can decrease C═C adsorption and promote H* formation, enabling semihydrogenation of alkynes with high selectivity and FEs at lower potentials. Then, creating high-curvature nanotips to concentrate the substrates further speeds up the hydrogenation process. (ii) By introducing low-coordination sites into Fe and combining low-coordination sites and surface fluorine to modify Co to optimize the adsorption of intermediates and facilitate H* formation, hydrogenation of nitriles and N-heterocycles with high activity and selectivity is obtained. (iii) By forming isolated Pd sites to induce a specific σ-alkynyl adsorption of alkynes and steering S vacancies of Co₃S_4-x to preferentially adsorb -NO₂, hydrogenation of easily reduced group-decorated alkynes and nitroarenes with high chemoselectivity is realized. (iv) For gas reactant participated reactions, by designing hydrophobic gas diffusion layer-supported ultrasmall Cu nanoparticles to enhance mass transfer, improve H₂O activation, inhibit H₂ formation, and decrease ethylene adsorption, ampere-level ethylene production with a 97.7% FE is accomplished. Finally, we provide an outlook on the current challenges and promising opportunities in this area. We believe that the electrode selection principles summarized here provide a paradigm for designing highly active and selective nanomaterials to achieve electrocatalytic hydrogenation and other organic transformations with fascinating performances.

Plasma-Induced Oxygen Vacancies in N-Doped Hollow NiCoPBA Nanocages Derived from Prussian Blue Analogue for Efficient OER in Alkaline Media

Although water splitting is a promising method to produce clean hydrogen energy, it requires efficient and low-cost catalysts for the oxygen evolution reaction (OER). This study focused on plasma treatment's significance of surface oxygen vacancies in improving OER electrocatalytic activity. For this, we directly grew hollow NiCoPBA nanocages using a Prussian blue analogue (PBA) on nickel foam (NF). The material was treated with N plasma, followed by a thermal reduction process for inducing oxygen vacancies and N doping on the structure of NiCoPBA. These oxygen defects were found to play an essential role as a catalyst center for the OER in enhancing the charge transfer efficiency of NiCoPBA. The N-doped hollow NiCoPBA/NF showed excellent OER performance in an alkaline medium, with a low overpotential of 289 mV at 10 mA cm^-2 and a high stability for 24 h. The catalyst also outperformed a commercial RuO₂ (350 mV). We believe that using plasma-induced oxygen vacancies with simultaneous N doping will provide a novel insight into the design of low-priced NiCoPBA electrocatalysts.

Understanding Synergistic Catalysis on Cu-Se Dual Atom Sites via Operando X-ray Absorption Spectroscopy in Oxygen Reduction Reaction

The construction and understanding of synergy in well-defined dual-atom active sites is an available avenue to promote multistep tandem catalytic reactions. Herein, we construct a dual-hetero-atom catalyst that comprises adjacent Cu-N₄ and Se-C₃ active sites for efficient oxygen reduction reaction (ORR) activity. Operando X-ray absorption spectroscopy coupled with theoretical calculations provide in-depth insights into this dual-atom synergy mechanism for ORR under realistic device operation conditions. The heteroatom Se modulator can efficiently polarize the charge distribution around symmetrical Cu-N₄ moieties, and serve as synergistic site to facilitate the second oxygen reduction step simultaneously, in which the key OOH*-(Cu₁ -N₄ ) transforms to O*-(Se₁ -C₂ ) intermediate on the dual-atom sites. Therefore, this designed catalyst achieves satisfied alkaline ORR activity with a half-wave potential of 0.905 V vs. RHE and a maximum power density of 206.5 mW cm^-2 in Zn-air battery.

Synthetic carbon nanomaterials for electrochemical energy conversion

Carbon nanomaterials have attracted widespread attention in electrochemical energy conversion due to their large surface area, excellent electrical/thermal conductivity and good chemical stability. However, the structure-activity relationship of carbon nanomaterials remains unclear. This review is thus on the synthesis methods of carbon nanomaterials including two-dimensional graphene, graphene nanoribbons, nanographene, heteroatom doped porous carbon and graphdiyne as electrocatalysts for the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction in fuel cells, electrolyzers and CO₂ reduction. The correlation between the electronic/chemical properties and electrochemical performance of synthetic carbon nanostructures will be profoundly discussed. Additionally, the emerging challenges and some perspectives on the development of synthetic carbon nanomaterials for electrochemical energy conversion are discussed.

Electrosynthesis of H2O2 through a two-electron oxygen reduction reaction by carbon based catalysts: From mechanism, catalyst design to electrode fabrication

Hydrogen peroxide (H₂O₂) is an efficient oxidant with multiple uses ranging from chemical synthesis to wastewater treatment. The in-situ H₂O₂ production via a two-electron oxygen reduction reaction (ORR) will bring H₂O₂ beyond its current applications. The development of carbon materials offers the hope for obtaining inexpensive and high-performance alternatives to substitute noble-metal catalysts in order to provide a full and comprehensive picture of the current state of the art treatments and inspire new research in this area. Herein, the most up-to-date findings in theoretical predictions, synthetic methodologies, and experimental investigations of carbon-based catalysts are systematically summarized. Various electrode fabrication and modification methods were also introduced and compared, along with our original research on the air-breathing cathode and three-phase interface theory inside a porous electrode. In addition, our current understanding of the challenges, future directions, and suggestions on the carbon-based catalyst designs and electrode fabrication are highlighted.

Degradation of sulfamethoxazole using PMS activated by cobalt sulfides encapsulated in nitrogen and sulfur co-doped graphene

In this study cobalt sulfides (Co₉S₈) coated on the nitrogen and sulfur co-doped graphene (Co₉S₈@S-N-RG) was firstly prepared and used for degradation of antibiotic sulfamethoxazole (SMX). The results showed that SMX could be completely degraded by Co₉S₈@S-N-RG-activated peroxymonosulfate (PMS) within 20 min with its mineralization efficiency of 38.7%. The SMX degradation rate followed pseudo first-order kinetics with kinetic constant of 0.377 min^-1 that was higher than that induced by Co₉S₈, N-RG, S-N-RG and Co₉S₈@S-RG, indicating Co₉S₈@S-N-RG had superior catalytic activity. Co₉S₈@S-N-RG can activate PMS to produce sulfate radicals and hydroxyl radicals, while sulfate radicals played major role. Co₉S₈ participated in PMS activation in which Co²⁺ was involved in sulfate radicals formation, while sulfur species facilitated the conversion of Co³⁺ to Co²⁺. In addition, carbon defects, CO, pyridinic N and pyrrolic N also contributed to PMS activation.The superior catalytic activity was attributed to the synergistic effect of Co₉S₈ and S-N-RG. This study could provide an efficient and stable PMS activator, and insight into the PMS activation mechanism by Co₉S₈@S-N-RG.

CO2 Electroreduction over Metallic Oxide, Carbon-Based, and Molecular Catalysts: A Mini-Review of the Current Advances

Electrochemical CO2 reduction reaction (CO2RR) is one of the most challenging targets of current energy research. Multi-electron reduction with proton-coupled reactions is more thermodynamically favorable, leading to diverse product distribution. This requires the design of stable electroactive materials having selective product generation and low overpotentials. In this review, we have explored different CO2RR electrocatalysts in the gas phase and H-cell configurations. Five groups of electrocatalysts ranging from metals and metal oxide, single atom, carbon-based, porphyrins, covalent, metal–organic frameworks, and phthalocyanines-based electrocatalysts have been reviewed. Finally, conclusions and prospects have been elaborated.

In situ coating of a N, S co-doped porous carbon thin film on carbon nanotubes as an advanced metal-free bifunctional oxygen electrocatalyst for Zn–air batteries

A N, S co-doped porous carbon thin film was coated in situ on CNT via a simple and scalable polymerization-pyrolysis strategy, which exhibits extraordinary ORR/OER performance in half-cell tests and Zn–air batteries.

Nanostructured Carbon Electrocatalysts for Energy Conversions

The growing energy demand worldwide has led to increased use of fossil fuels. This, in turn, is making fossil fuels dwindle faster and cause more negative environmental impacts. Thus, alternative, environmentally friendly energy sources such as fuel cells and electrolyzers are being developed. While significant progress has already been made in this area, such energy systems are still hard to scale up because of their noble metal catalysts. In this concept paper, first, various scalable nanocarbon-based electrocatalysts that are being synthesized for energy conversions in these energy systems are introduced. Next, notable heteroatom-doping and nanostructuring strategies that are applied to produce different nanostructured carbon materials with high electrocatalytic activities for energy conversions are discussed. The concepts used to develop such materials with different structures and large density of dopant-based catalytic functional groups in a sustainable way, and the challenges therein, are emphasized in the discussions. The discussions also include the importance of various analytical, theoretical, and computational methods to probe the relationships between the compositions, structures, dopants, and active catalytic sites in such materials. These studies, coupled with experimental studies, can further guide innovative synthetic routes to efficient nanostructured carbon electrocatalysts for practical, large-scale energy conversion applications.

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

Nitrogen doping sludge-derived biochar to activate peroxymonosulfate for degradation of sulfamethoxazole: Modulation of degradation mechanism by calcination temperature

The surface property of biochar can be modulated through nitrogen doping and calcination temperature. In this study, nitrogen-doped sludge-derived biochar (NSDB) was prepared and applied to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) degradation, focusing on the effect of calcination temperature on the degradation mechanism. The results showed that the contribution of free radicals to SMX degradation decreased gradually when calcination temperature increased from 300 to 800 °C. In contrast, the contribution of surface-bound reactive species increased gradually. However, the contribution of surface-bound reactive species to SMX degradation decreased for NSDB prepared at 900 °C. The change of physiochemical properties such as contact angle caused by calcination temperature was responsible for the shift of SMX degradation mechanism. NSDB prepared at 800 °C showed higher catalytic activity to PMS compared to NSDB prepared at other temperatures. Compared to sludge-derived biochar (SDB), NSDB had much higher catalytic activity, indicating that nitrogen doping could improve the catalytic activity of SDB. This study provided a way to modulate the degradation mechanism of SMX by calcination temperature of biochar to activate PMS for degradation of organic pollutants.

Recent Advances on Heteroatom-Doped Porous Carbon/Metal Materials: Fascinating Heterogeneous Catalysts for Organic Transformations

Design and preparation of low-cost, effective, and novel catalysts are important topics in the field of heterogeneous catalysis from academic and industrial perspectives. Recently, heteroatom-doped porous carbon/metal materials have received significant attention as promising catalysts in divergent organic reactions. Incorporation of heteroatom into the carbon framework can tailor the properties of carbon, providing suitable interaction between support and metal, resulting in superior catalytic performance compared with those of traditional pure carbon/metal catalytic systems. In this review, we try to underscore the recent advances in the design, preparation, and application of heteroatom-doped porous carbon/metal catalysts towards various organic transformations.

The role of supported dual-atom on graphitic carbon nitride for selective and efficient CO2electrochemical reduction

The electrochemical reduction of CO₂into value-added fuels and chemicals using single atom (SACs) or dual-atom catalysts (DACs) has been extensively studied, but the reaction mechanism and design rules are still unclear. Here, we studied the role of dual-metal atoms on graphite carbon nitride (M₁M₂@g-CN, M₁M₂ = CuCu, FeFe, RuRu, RuCu, RuFe, CuFe) for selective and efficient CO₂electrochemical reduction based on density functional theory. Our results show that CO₂RR on RuRu@g-CN catalyst prefers the *COOH pathway, while for CuCu@g-CN, FeFe@g-CN, RuCu@g-CN, RuFe@g-CN, CuFe@g-CN catalysts, the *OCHO pathway is more suitable. Among all the DACs combinations, we found that RuCu@g-CN and RuFe@g-CN are the most promising electrocatalysts for CO₂RR with a lower limiting potential, which is attributed to the synergistic effect of different O- and C-affinity of the heterocenters in DACs. The selectivity of RuCu@g-CN and RuFe@g-CN to the production of CH₄is better than that of H₂evolution. In addition, we also found that the adsorption free energy of intermediate on heteroatomic DACs can be predicted by those on homoatomic DACs, which can be used to further predict the limiting potential.

Recent advances in metal-free heteroatom-doped carbon heterogonous catalysts

The development of cost-effective, efficient, and novel catalytic systems is always an important topic for heterogeneous catalysis from academia and industrial points of view. Heteroatom-doped carbon materials have gained more and more attention as effective heterogeneous catalysts to replace metal-based catalysts, because of their excellent physicochemical properties, outstanding structure characteristics, environmental compatibility, low cost, inexhaustible resources, and low energy consumption. Doping of heteroatoms can tailor the properties of carbons for different utilizations of interest. In comparison to pure carbon catalysts, these catalysts demonstrate superior catalytic activity in many organic reactions. This review highlights the most recent progress in synthetic strategies to fabricate metal-free heteroatom-doped carbon catalysts including single and multiple heteroatom-doped carbons and the catalytic applications of these fascinating materials in various organic transformations such as oxidation, hydrogenation, hydrochlorination, dehydrogenation, etc.

Recent advances in metal-free heteroatom-doped carbon heterogeneous catalysts including the preparation methods and their catalytic applications in various organic reactions have been reported.

MOFs-Derived Carbon-Based Metal Catalysts for Energy-Related Electrocatalysis

Electrochemical devices, as renewable and clean energy systems, display a great potential to meet the sustainable development in the future. However, well-designed and highly efficient electrocatalysts are the technological dilemmas that retard their practical applications. Metal-organic frameworks (MOFs) derived electrocatalysts exhibit tunable structure and intriguing activity and have received intensive investigation in recent years. In this review, the recent progress of MOFs-derived carbon-based single atoms (SAs) and metal nanoparticles (NPs) catalysts for energy-related electrocatalysis is summarized. The effects of synthesis strategy, coordination environment, morphology, and composition on the catalytic activity are highlighted. Furthermore, these SAs and metal NPs catalysts for the applications of electrocatalysis (hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, carbon dioxide reduction reaction, and nitrogen reduction reaction) are overviewed. Finally, some current challenges and foresighted ideas for MOFs-derived carbon-based metal electrocatalysts are presented.

Recent progress in pristine MOF-based catalysts for electrochemical hydrogen evolution, oxygen evolution and oxygen reduction

Among various kinds of materials that have been investigated as electrocatalysts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), metal-organic frameworks (MOFs) has emerged as a promising material for electrocatalyzing these vital processes owing to their structural merits that integrate advantages of both homogeneous and heterogeneous catalysts; however there is still big room for their improvement in terms of inferior activity and poor conductivity, as well as the ambiguity of real active sites. In this review, advanced strategies with the aim of solving the activity and conductivity problems are summarized as microstructure engineering and conductivity improvement, respectively. The structural evolution of some MOFs and their real active species has also been discussed. Finally, perspectives on the development of MOF materials for HER, OER and ORR electrocatalysis are provided.

Atomic-Level Electronic Properties of Carbon Nitride Monolayers

Heteroatom-doped carbon-based materials are of significance for clean energy conversion and storage because of their fascinating electronic properties, low cost, high durability, and environmental friendliness. Atomically precise fabrication of carbon-based materials with well-defined heteroatom-dopant positions and atomic-scale understanding of their atomic-level electronic properties is a challenge. Herein, we demonstrate the bottom-up on-surface synthesis of 1D and 2D monolayer carbon nitride nanostructures with precise control of the nitrogen-atom doping sites and pore sizes. We also observe an electronic band offset at the C-N heterojunction. Using high-resolution scanning tunneling microscopy, the atomic structure of the as-prepared carbon nitride nanoporous monolayers are revealed, indicating successful and precise control of the structures and N atom doping sites. Furthermore, corroborated by theoretical calculations, scanning tunneling spectroscopy measurements reveal a valence band shift of 140 meV that results in an electric field of 2.9 × 10⁸ V m^-1 at the C-N heterojunction, indicating efficient separation of the electron-hole pair at the N doping site. Our finding offers direct atomic-level insights into the local electronic structure of the heteroatom-doped carbon-based materials.

Improving the Performance of Zn-Air Batteries with N-Doped Electroexfoliated Graphene

The constantly growing demand for active, durable, and low-cost electrocatalysts usable in energy storage devices, such as supercapacitors or electrodes in metal-air batteries, has triggered the rapid development of heteroatom-doped carbon materials, which would, among other things, exhibit high catalytic activity in the oxygen reduction reaction (ORR). In this article, a method of synthesizing nitrogen-doped graphene is proposed. Few-layered graphene sheets (FL-graphene) were prepared by electrochemical exfoliation of commercial graphite in a Na2SO4 electrolyte with added calcium carbonate as a separator of newly-exfoliated FL-graphene sheets. Exfoliated FL-graphene was impregnated with a suspension of green algae used as a nitrogen carrier. Impregnated FL-graphene was carbonized at a high temperature under the flow of nitrogen. The N-doped FL-graphene was characterized through instrumental methods: high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Electrochemical performance was determined using cyclic voltamperometry and linear sweep voltamperometry to check catalytic activity in ORR. The N-doped electroexfoliated FL-graphene obeyed the four-electron transfer pathways, leading us to further test these materials as electrode components in rechargeable zinc-air batteries. The obtained results for Zn-air batteries are very important for future development of industry, because the proposed graphene electrode materials do not contain any heavy and noble metals in their composition.

Current Trends in the Application of Nanomaterials for the Removal of Emerging Micropollutants and Pathogens from Water

Water resources contamination has a worldwide impact and is a cause of global concern. The need for provision of clean water is becoming more and more demanding. Nanotechnology may support effective strategies for the treatment, use and reuse of water and the development of next-generation water supply systems. The excellent properties and effectiveness of nanomaterials make them particularly suitable for water/wastewater treatment. This review provides a comprehensive overview of the main categories of nanomaterials used in catalytic processes (carbon nanotubes/graphitic carbon nitride (CNT/g-C₃N₄) composites/graphene-based composites, metal oxides and composites, metal–organic framework and commercially available nanomaterials). These materials have found application in the removal of different categories of pollutants, including pharmaceutically active compounds, personal care products, organic micropollutants, as well as for the disinfection of bacterial, viral and protozoa microbial targets, in water and wastewater matrices. Apart from reviewing the characteristics and efficacy of the aforementioned nanoengineered materials for the removal of different pollutants, we have also recorded performance limitations issues (e.g., toxicity, operating conditions and reuse) for their practical application in water and wastewater treatment on large scale. Research efforts and continuous production are expected to support the development of eco-friendly, economic and efficient nanomaterials for real life applications in the near future.

Potential-tuned selective electrosynthesis of azoxy-, azo- and amino-aromatics over a CoP nanosheet cathode

Azoxy-, azo- and amino-aromatics are among the most widely used building blocks in materials science pharmaceuticals and synthetic chemistry, but their controllable and green synthesis has not yet been well established. Herein, a facile potential-tuned electrosynthesis of azoxy-, azo- and amino-aromatics via aqueous selective reduction of nitroarene feedstocks over a CoP nanosheet cathode is developed. A series of azoxy-, azo- and amino-compounds with excellent selectivity, good functional group tolerance and high yields are produced by applying different bias input. The synthetically significant and challenging asymmetric azoxy-aromatics can be controllably synthesized in moderate to good yields. The use of water as the hydrogen source makes this strategy remarkably fascinating and promising. In addition, deuterated aromatic amines with a high deuterium content can be readily obtained by using D2O. By pairing with anodic oxidation of aliphatic amines to nitriles, synthetically useful building blocks can be simultaneously produced in a CoP||Ni2P two-electrode electrolyzer. Only 1.25 V is required to achieve a current density of 20 mA cm-2, which is much lower than that of overall water splitting (1.70 V). The paired oxidation and reduction reactions can also be driven using a 1.5 V battery to synthesize nitrile and azoxybenzene with good yields and selectivity, further emphasizing the flexibility and controllability of our method. This work paves the way for a promising approach to the green synthesis of valuable chemicals through potential-controlled electrosynthesis.

Recent Advances in Oxygen Electrocatalysts Based on Perovskite Oxides

Electrochemical oxygen reduction and oxygen evolution are two key processes that limit the efficiency of important energy conversion devices such as metal–air battery and electrolysis. Perovskite oxides are receiving discernable attention as potential bifunctional oxygen electrocatalysts to replace precious metals because of their low cost, good activity, and versatility. In this review, we provide a brief summary on the fundamentals of perovskite oxygen electrocatalysts and a detailed discussion on emerging high-performance oxygen electrocatalysts based on perovskite, which include perovskite with a controlled composition, perovskite with high surface area, and perovskite composites. Challenges and outlooks in the further development of perovskite oxygen electrocatalysts are also presented.