Fabricating Metal@N-Doped Carbon Catalysts via a Thermal Method

From Atomic-Level Synthesis to Device-Scale Reactors: A Multiscale Approach to Water Electrolysis

ConspectusThe development of an advanced energy conversion system for water electrolysis with high efficiency and durability is of great significance for a hydrogen-powered society. This progress relies on the fabrication of electrocatalysts with superior electrochemical performance. Despite decades of advancements in exploring high-performance noble and non-noble metal electrocatalysts, several challenges persist at both the micro- and macrolevels in the field of water electrolysis.At the microlevel, which encompasses electrocatalyst synthesis and characterization, design strategies for high-performance electrocatalysts have primarily focused on interface chemical engineering. However, comprehensive understanding and investigation of interface chemical engineering across various length scales, from micrometers to atomic scales, are still lacking. This deficiency hampers the rational design of catalysts with optimal performance. Under harsh reaction conditions, such as high bias potential and highly acidic or alkaline media, the surface of catalyst materials is susceptible to undergoing "reconstruction", deviating from what is observed through ex situ characterization techniques postsynthesis. Conventional ex situ characterization methods do not provide an accurate depiction of the catalyst's structural evolution during the electrocatalytic reaction, hindering the exploration of the catalytic mechanism.At the macrolevel, pertaining to catalysis-performance evaluation systems and devices, traditional laboratory settings employ a conventional three-electrode or two-electrode system to assess the catalytic performance of electrocatalysts. However, this approach does not accurately simulate hydrogen production under realistic industrial conditions, such as elevated temperatures (60-70 °C), high current densities exceeding 0.5 A cm-2, and flowing electrolytes. To address this limitation, it is crucial to develop testing equipment and methodologies that replicate the actual industrial conditions.In this Account, we propose a multiscale research framework for water electrolysis, spanning from microscale synthesis to macroscale scaled reactor design. Our approach focuses on the design and evaluation of high-performance HER/OER (hydrogen evolution reaction/oxygen evolution reaction) electrocatalysts, incorporating the following strategies: Leveraging principles of interface chemical engineering across various length scales (micrometers, nanometers, and atoms) enables the design of catalyst materials that enhance both activity and durability. This approach provides a comprehensive understanding of the intricate interplay between the catalyst structure and activity, implementing in situ/operando characterization techniques to monitor dynamic interfacial reactions and surface reconstruction processes. This facilitates a profound exploration of catalytic reaction mechanisms, offering insights into the catalyst's structural evolution during the electrocatalytic reaction. We construct a laboratory-scale membrane electrode assembly (MEA) electrochemical reactor capable of operating at high current densities (>1 A cm-2) to evaluate the electrocatalytic performance under simulated industrial conditions. This ensures objective and authentic assessments of the catalyst application potential. Throughout the following sections, we illustrate the application of interface chemical engineering on different length scales in designing diverse electrocatalyst materials. We rely on in situ characterization techniques to gain a profound understanding of the mechanisms behind the HER and OER. Additionally, we describe the development of both acidic and alkaline MEA electrochemical reactors to enhance the precision of electrocatalytic performance evaluation. Finally, we provide a concise overview of the challenges and opportunities in this field.

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.

Biomass-Derived Carbon-Based Multicomponent Integration Catalysts for Electrochemical Water Splitting

Electrocatalytic water splitting powered by sustainable electricity is a crucial approach for the development of new generation green hydrogen technology. Biomass materials are abundant and renewable, and the application of catalysis can increase the value of some biomass waste and turn waste into fortune. Converting economical and resource-rich biomass into carbon-based multicomponent integrated catalysts (MICs) has been considered as one of the most promising ways to obtain inexpensive, renewable and sustainable electrocatalysts in recent years. In this review, recent advances in biomass-derived carbon-based MICs towards electrocatalytic water splitting are summarized, and the existing issues and key aspects in the development of these electrocatalysts are also discussed and prospected. The application of biomass-derived carbon-based materials will bring some new opportunities in the fields of energy, environment, and catalysis, as well as promote the commercialization of new nanocatalysts in the near future.

A general method for rapid synthesis of refractory carbides by low-pressure carbothermal shock reduction

Refractory carbides are attractive candidates for support materials in heterogeneous catalysis because of their high thermal, chemical, and mechanical stability. However, the industrial applications of refractory carbides, especially silicon carbide (SiC), are greatly hampered by their low surface area and harsh synthetic conditions, typically have a very limited surface area (<200 m² g^-1), and are prepared in a high-temperature environment (>1,400 °C) that lasts for several or even tens of hours. Based on Le Chatelier's principle, we theoretically proposed and experimentally verified that a low-pressure carbothermal reduction (CR) strategy was capable of synthesizing high-surface area SiC (569.9 m² g^-1) at a lower temperature and a faster rate (∼1,300 °C, 50 Pa, 30 s). Such high-surface area SiC possesses excellent thermal stability and antioxidant capacity since it maintained stability under a water-saturated airflow at 650 °C for 100 h. Furthermore, we demonstrated the feasibility of our strategy for scale-up production of high-surface area SiC (460.6 m² g^-1), with a yield larger than 12 g in one experiment, by virtue of an industrial viable vacuum sintering furnace. Importantly, our strategy is  also applicable to the rapid synthesis of refractory metal carbides (NbC, Mo₂C, TaC, WC) and even their emerging high-entropy carbides (VNbMoTaWC₅, TiVNbTaWC₅). Therefore, our low-pressure CR method provides an alternative strategy, not merely limited to temperature and time items, to regulate the synthesis and facilitate the upcoming industrial applications of carbide-based advanced functional materials.

ZIF-Derived Metal/N-Doped Porous Carbon Nanocomposites: Efficient Catalysts for Organic Transformations

Recently, zeolitic imidazolate framework (ZIF)-derived metal/N-doped porous carbon nanocomposites (M@NCs) have emerged as a class of appealing heterogeneous catalysts applied in organic synthesis, and the striking features mainly involve low-cost...

Fe–FeOx nanoparticles encapsulated in N-doped carbon material: a facile catalyst for selective synthesis of quinazolines from alcohols in water

A Fe–FeOx@NC catalyst with N-doped carbon encapsulated Fe–FeOx nanoparticles has excellent performance in the synthesis of quinazolines.

Highly dispersed palladium nanoclusters anchored on nanostructured hafnium(iv) oxide as highly efficient catalysts for the Suzuki–Miyaura coupling reaction

Pd@HfO2 derived via two-step pyrolysis of Pd@NH2-UiO-66(Hf) exhibited high catalytic activity for the Suzuki–Miyaura coupling reactions.

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.

Preparation of palladated porous nitrogen-doped carbon using halloysite as porogen: disclosing its utility as a hydrogenation catalyst

In this article, halloysite nanoclay (Hal) was used as porogen for the synthesis of nitrogen doped porous carbon material with high specific surface area and pore volume. To this purpose, polymerization of melamine and terephthalaldehyde (MT) was performed in the presence of amine-functionalized carbon coated Hal (Hal@Glu-2N) that was prepared from hydrothermal treatment of Hal and glucose. Then, the prepared nanocomposite was palladated and carbonized to afford Pd@Hal@C. To further improve the textural properties of the nanocomposite, and introduce more pores in its structure, Hal nanotubes were etched. The characterization of the resulting compound, Pd@C, and comparing it with Pd@Hal@C, showed that etching of Hal significantly increased the specific surface area and pore volume in Pd@C. Pd@C was successfully used as a heterogeneous catalyst for promoting hydrogenation of nitroarens in aqueous media using hydrogen with atmospheric pressure as a reducing agent. The comparison of the structural features and catalytic activity of the catalyst with some control catalysts, including, Pd@Hal, Pd@Hal@Glu, Pd@Hal@Glu-MT and Pd@Hal@C confirmed that nitrogen groups in C could improve the Pd anchoring and suppress its leaching, while etching of Hal and introduction of more pores could enhance the catalytic activity through facilitating the mass transfer.

Biomass-derived ordered mesoporous carbon nano-ellipsoid encapsulated metal nanoparticles inside: ideal nanoreactors for shape-selective catalysis

Ordered mesoporous nano-ellipsoids were synthesized by hydrothermal carbonization of biomass derivatives. Their multifunctional features have been demonstrated and the ability of encapsulating metal nanoparticles (NPs) is presented.

Water-assisted one-pot synthesis of N-doped carbon supported Ru catalysts for heterogeneous catalysis

For the first time, a simple yet efficient water-assisted one-pot pyrolysis (WAOP) strategy was developed to in situ liberate the inaccessible Ru active sites confined inside N-doped carbon. The liberated Ru/CN catalysts exhibit a 9-fold improvement in catalytic activity for quinoline hydrogenation compared with catalysts obtained from the water-free pyrolysis process, and high tolerance for selective hydrogenation of various quinolines substituted with different functional groups. We anticipate that WAOP addresses a key issue that currently plagues carbon-based catalyst synthesis and should lead to improvements in fields as diverse as chemical production and environmental protection.

Sustainable route for the synthesis of flower-like Ni@N-doped carbon nanosheets from bagasse and its catalytic activity towards reductive amination of nitroarenes with bio-derived aldehydes

Waste derived N-doped carbon for one pot domino catalytic transformation starting from nitroarenes and carbonyl compounds directed towards the preparation of imines and benzimidazole products.

All-around coating of CoNi nanoalloy using a hierarchically porous carbon derived from bimetallic MOFs for highly efficient hydrolytic dehydrogenation of ammonia-borane

In situ synthesis of core–shell carbon enclosed CoNi alloys achieves efficient heterogeneous catalysis.

Substrate-free and label-free electrocatalysis-assisted biosensor for sensitive detection of microRNA in lung cancer cells

We develop a substrate-free and label-free electrocatalysis-assisted biosensor for sensitive detection of microRNA using the iron-embedded nitrogen-rich carbon nanotubes (FeCN) as the catalytic elements. This biosensor exhibits excellent selectivity and high sensitivity with a detection limit of 8.53 × 10^-16 M and a large dynamic range of 6 orders of magnitude. It can be further applied for accurate quantification of microRNA in lung cancer cells.

Synthesis of carbazole-based microporous polymer networks via an oxidative coupling mediated self-assembly strategy: from morphology regulation to application analysis

An efficient strategy to prepare morphology-tunable carbazole-based microporous polymer networks (C-MPNs) via an oxidative coupling mediated self-assembly strategy is reported for the first time.