Water electrolysis for hydrogen harvesting has become a research hotspot in both academia and industry due to its low carbon emissions, high energy efficiency, and high purity, which offer significant advantages over the majority of hydrogen production technologies. Thereinto, the electrocatalytic hydrogen reaction (HER) is at the core, which aways involves a multi-step hydrogen transfer process and multiple active sites working together. However, catalytic correlations between those active sites and potential hydrogen spillover effects involved are often overlooked. In this paper, we first review the hydrogen evolving properties and reaction mechanisms in electrocatalytic systems such as transition metal oxides, phosphides, and sulfides. By combining traditional theories of thermal catalysis, active sites involved in hydrogen spillover are then conceptually summarized into both the primary and secondary active sites, elucidating their catalytic relevance and functional differences. This paper will not only provide a design concept for the creation of efficient and inexpensive electrocatalysts for hydrogen evolution, but also serve as a useful reference for further studies of hydrogen transfer behaviors in other hydrogen-involved electrocatalytic reactions.

The intrinsic activity of single-atom catalysts is influenced by the local electronic structures of metal centers, with existing modulation strategies limited to adjacent atomic coordination. However, the impacts of support surface geometry on local bonding environment, and thus electronic structures of single-atom centers have rarely been known. Here, we prepared highly curved B,N co-doped carbon-supported ruthenium catalyst with an ultra-low Ru loading of 0.4wt%, which exhibited an ultrahigh turnover frequency (TOF) of 10 H2 s-1 (38 times that of Pt/C) and superior stability in alkaline hydrogen evolution reaction (HER). We found that curving support surface induced the strain, resulting in 1.5% compressed Ru-N and 4% stretched Ru-B bonds, leading to the accumulation of positive charge and quenching of spin polarization at Ru sites, thereby achieving the optimal binding of H* and enhanced performance for HER. This work highlights the significant support effects upon the structural design of active sites.

Mesocrystals (MCs) with high-index facets may have superior catalytic properties to those with low-index facets and their nanocrystal counterparts. However, synthesizing such mesocrystal materials is still very challenging because of the metastability of MCs and energetic high-index crystal facets. This work reports a successful solvothermal method followed by calcination for synthesizing copper oxide-based MCs possessing a core-shell structure (denoted as Cu2O@CuO HIMCs). Furthermore, these MCs are predominantly bounded by the high-index facets such as {311} or {312} with a high-density of stepped atoms. When used as catalysts in Si hydrochlorination to produce trichlorosilane (TCS, the primary feedstock of high-purity crystalline Si), Cu2O@CuO HIMCs exhibit significantly enhanced Si conversion and TCS selectivity compared to those with flat surfaces and their nanostructured counterparts. Theoretical calculations reveal that both the core-shell structure and the high-index surface contribute to the increased electron density of Cu sites in Cu2O@CuO HIMCs, promoting the adsorption and dissociation of HCl and stabilizing the dissociated Cl* intermediate. This work provides a simple method for synthesizing high-index faceted MCs and offers a feasible strategy to enhance the catalytic performance of MCs.

Developing high-performance and low-cost electrocatalysts toward methanol oxidation reaction (MOR) is essential for fuel cell applications. Herein, we report a defect engineering strategy integrating amorphization and phosphorization to construct directly interconnected networks of amorphous NiCo-based metal-organic framework nanowires (a-NiCo-MOFNWs) with phosphorus (P) doping. The resulting P-doped a-NiCo-MOFNWs (a-NiCo-MOFNWs-P) network displays superior MOR efficiency and long-term durability over 1000 cyclic voltammetry (CV) measurements. The special structure of directly interconnected networks and the synergistic effect between the amorphous MOFs and dispersed phosphorus species give rise to abundant exposed active sites, accelerated electron transport, and increased porosity for mass transfer, thus boosting the reaction kinetics of MOR. This work provides additional insights into the network assembly and structural evolution of one-dimensional (1D) MOFs, and also opens up new avenues for the design of highly reactive and robust non-precious metal-based electrocatalysts.

自工业革命以来,人类经济社会发展依赖于过度消耗化石燃料,导致严重的能源危机;产生的大量CO 2 排放到大气中,也给生态环境带来巨大的威胁 [1] .在这种背景下,利用间歇式可再生电力驱动水电解获得“绿氢”,进而发展氢循环经济,将为加快实现“双碳”目标提供一种重要的解决方案.

Currently, green hydrogen harvesting from electrochemical water splitting is overly reliant on noble metals with high catalytic activity but low natural abundance and high cost. As one of potential earth‐abundant alternatives, copper, however, displays a poor hydrogen evolving capability, mainly due to inherently a weak hydrogen binding energy (HBE). It poses a substantial restriction to metallic Cu alone serving as primary active sites for high‐performance hydrogen evolution. Thanks to the presence of hydrogen spillover that was often overlooked during the electrocatalysis, the hydrogen evolution in a nonacidic electrolyte can be accelerated by the recombination desorption of adsorbed hydrogen over Cu with a weak HBE. Here, we concisely highlighted this promotion effect of secondary active Cu on electrocatalytic hydrogen evolution and eagerly expected to extend hydrogen spillover effects to the advance of multi‐site electrocatalytic systems.

The increasing demand for fine and high-value-added chemicals has motivated the lasting exploration of high-performance catalysts with desirable activity, selectivity, and durability [...]

Selective catalytic reduction of NOx by CO (CO-SCR) to both N2 and CO2 is a promising way to simultaneously remove two harmful gases, CO and NOx, in automobile and factory exhaust gases. The development of efficient catalysts is the key challenge for the technology to be commercialized. The low-cost Cu-based catalysts have shown promising performance in CO-SCR, but there are some technical problems that obstruct their practical implementation, such as high reduction temperature and low O2, H2O, and SO2 resistance. This paper provides a comprehensive overview and insights into CO-SCR under O2-containing conditions over the Cu-based catalysts, including catalytic performances of non-supported, supported mono-metallic, supported bimetallic, and supported multi-metallic Cu-based catalysts. In addition, the effects of O2 concentration, reaction temperature, H2O, and SO2 on the catalytic performance are discussed. Furthermore, the reaction mechanism of CO-SCR on Cu-based catalysts is briefly summarized. Lastly, challenges and perspectives with respect to this reaction are discussed. We hope this work can provide theoretical guidance for the rational design of efficient Cu-based catalysts in the CO-SCR reaction for commercial applications.

The oxidation of mercaptans under mild and base-free conditions is of vital importance in terms of economy and environment for petroleum processing industry. Here, we developed a series of MOF-derived cobalt-based nitrogen-doped (N-doped) carbon (Co/CN-x) catalysts for the base-free catalytic oxidation of mercaptans. The optimal Co/CN-900 showed excellent catalytic activity for the oxidation of mercaptans under base-free conditions, yielding complete conversion of various mercaptans and > 99.0% selectivity of disulfides. The high performance can be contributed to the advantages of hierarchical pore structure for the diffusion and migration of substrates, self-carrying alkalinity for the formation of mercaptide anion, abundant active Co sites for catalytic oxidation of mercaptans as well as the synergistic effects between the Co nanoparticles (NPs) and N-doped carbon supports. Furthermore, a possible mechanism for base-free catalytic oxidation of mercaptans over Co/CN-x catalysts is proposed based on a set of control experiments and density functional theory (DFT) calculations. (c) 2021 Elsevier Inc. All rights reserved.

Generating different types of defects in heterogeneous catalysts for synergetic promotion of the reactivity and selectivity in catalytic reactions is highly challenging due to the lack of effective theoretical guidance. Herein, we demonstrate a facile strategy to introduce two types of defects into the CuO-ZnO model catalyst, namely oxygen vacancies (OVs) induced by H-2 partial reduction and localized amorphous regions (LARs) generated via the ball milling process. Using industrially important Rochow-MUller reaction as a representative, we found OVs predominantly improved the target product selectivity of dimethyldichlorosilane, while LARs significantly increased the conversion of reactant Si. The CuO-ZnO catalyst with optimized OVs and LARs contents achieved the best catalytic property. Theoretical calculation further revealed that LARs promote the generation of the Cu3Si active phase, and OVs impact the electronic structure of the Cu3Si active phase. This work provides a new understanding of the roles of different catalyst defects and a feasible way of engineering the catalyst structure for better catalytic performances.

The pursuit of high performance in specific conditions motivated the grand development of synthetic methodologies for single-atom catalysts (SACs) in various research fields. In general, the existing methods for SACs could be simply classified into two main types- "bottom-up"and "top-down". The former was extensively explored and well documented elsewhere, whereas the latter is just on the rise. As it is, there is currently a lack of systematic overview for the top-down synthetic strategies to SACs. In this review, the rising top-down strategies are summarized in detail, including various thermo- and electrochemistry-based methods as well as other new protocols, based on the difference of metal-support interactions and energy input required during the atomization of bulk or micro- or nanoscale metal precursors. The introduction of the top-down synthetic strategies herein is believed to not only help establish the complete available methodology for task-specific SACs, but also contribute to the in-depth insights into the deactivation and regeneration mechanism of spent, supported metal catalysts for potential industrial application.

Controllable self-assembly is of great significance to the design and development of materials, determined by a complex interplay between the molecular interactions, kinetics, and entropic effects at the interface. So any comprehensive understanding of self-assembly behaviors was considered to be a challenge. We report a step-by-step mechanical action of the W-based complex powder and recorded the self-assembly behaviors like cine film with TEM images. The whole assembly process of a W-based complex from nanoparticle to nanosheets and, finally, to 1D well-shaped hollow nanotubes was presented completely. When affected by hydrogen bonding of water, the same complex was assembled to 3D spongy structures which transformated to an ultrathin 2D WO3 film with a superficial area as large as 80 mm(2) after heating at 700 degrees C.

? 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Numerous efforts have been devoted to investigating the catalytic events and disclosing the catalytic nature of the metal-carbon interaction interface. Nevertheless, the local deconstruction of catalytically active metal-carbon interface was still missing. Herein, the selected four types of landmark catalytic paradigms were highlighted, which was expected to clarify their essence and thus simplify the catalytic scenarios of the metal-carbon interface—carbon-supported metal nanoparticles, carbon-confined single-atom sites, chainmail catalysis, and the Mott-Schottky effect. The potential challenges and new opportunities were also proposed in the field. This perspective is believed to give an in-depth understanding of the catalytic nature of the metal-carbon interaction interface and in turn provide rational guidance to the delicate design of novel high-performance carbon-supported metal catalysts.

Hierarchical nanostructure with hollow feature can greatly promote electrocatalytic activity by facilitating the diffusion of active species and accelerating the contact between catalyst and electrolyte. In this paper, we report the preparation of hierarchical hollow NiFe hydroxide nanospheres assembled from ultrathin nanosheets as the OER electrocatalyst via a simple and gentle self-templating strategy, which includes two steps: the synthesis of Ni(OH)(2) nanospheres precursor and its further transformation to the final hollow-spheres after the introduction of Fe3+ via a mild hydrothermal method. The hollow NiFe hydroxide nanospheres were proven to be composed of ultrathin nanosheets which formed porous walls. This unique structure achieved numerous mass transfer channels for electrolytes, ideal pathways for ions and electrons, and a high specific surface area, leading to the improved performance for the product during the electrocatalytic reaction. In addition, the charge transfer rate and structural stability of the architecture have been greatly improved after the addition of Fe3+, which guaranteed high electrochemical performance toward OER. The tafel plot for NiFe-190 without any conductive agents is 60 mV dec(-1) and the overpotential needed to reach a current density of 10 mA cm(-2) is a 270 mV. (C) 2020 Elsevier Ltd. All rights reserved.

Conventional single thermal nature of phase change materials (PCMs) seriously obstructs their frontier applications. Herein, we designed advanced carbon nanotube (CNT) bundles assembled flexible hierarchical framework based phase change material composites for high-performance thermotherapy of allergic rhinitis. Hierarchically interconnected 3D freestanding flexible CNT sponge was constructed via a facile organic solvent-free route using table salt as a sacrificial template. The resulting hierarchical CNT sponge serves as an ideal compatible supporting host and polyethylene glycol (PEG) serves as an excellent thermal energy guest. Subsequently, we designed advanced portable integrated functional mask consisting of outer air purification layer and inner thermal regulation layer for the thermotherapy of allergic rhinitis, in which pristine CNT sponge serves as an excellent particulate matter capturer and PEG-infiltrated CNT sponge serves as a superior thermal regulator. Strikingly, our uniquely constructed flexible CNT sponge-involved composite PCMs assisted by polyvinylidene fluoride (PVDF) harvest high-performance thermotherapy (similar to 33 min of the plateau at similar to 43.5 degrees C). The corresponding medical results (HE staining and Wrights staining) further indicate that our designed thermotherapy mask can significantly reduce the inflammatory injury of nasal mucosa. Additionally, pristine hierarchical CNT sponge guarantees the inhaled air quality and enhances the thermotherapy effect. This synthetic strategy can be scaled up for large-scale production. This novel functional host-guest strategy creates an innovative platform for developing advanced multifunctional PCMs with multiple fascinating peculiarities and desired functional properties and teaches an old dog new tricks.

Currently, most reported composite phase change materials (PCMs) are powdery shape, which require secondary processing for practical applications. Although some monolithic composite PCMs have been developed, their flexibility usually undergoes a remarkable reduction or even complete disappearance when supporting materials are infiltrated with PCMs. To solve this problem, we fabricated a flexible supporting material with a folded layer-bridge network structure by dispersing carbon nanotubes (CNTs) in acetic acid solution of chitosan (CS) with poly(vinyl alcohol) (PVA) using a directional freezing method. Then CS/PVA/CNTs (CPC) scaffold was infiltrated with polyethylene glycol (PEG) to prepare PEG@CPC composite PCM. The resulting flexible composite PCM displays excellent mechanical properties, such as high tensile strength of 2.42 MPa and bending resistance of >100 cycles. Moreover, it displays outstanding thermal properties, such as high crystallinity of close to 100% and encapsulation ratio of 92.6 wt%. This work provides a simple method for preparation of flexible monolithic composite PCMs for many potential applications, such as wearable fitting-skin temperature-controlled materials.

The direct pyrolysis of metal organic frameworks (MOFs) has recently provided an effective method to prepare various metal-incorporated composite carbon materials. In this work, hierarchical Co-embedded N-doped porous carbon microspheres were synthesized by controlled pyrolysis of bimetallic Zn-Co Prussian blue analogues (PBAs), in which the metallic Zn component served as thermally removable template and ligand [Co(CN)(6)](3-) served as both Co and N sources. When devoted to catalyzing the reduction of 4-nitrophenol (4-NPh) into 4-aminophenol (4-APh), the optimized catalyst exhibited a large apparent rate constant of 1.35 min(-1) and high turnover frequency (TOF) of 0.0204 s(-1), which was superior to the majority of noble-metal-based catalysts. Besides, a home-made continuous flow catalysis system was readily constructed. Control experiments confirmed that both partially uncovered and totally inbuilt active metallic Co species acted as catalytically active sites. This work might provide a further understanding of the identification of active sites within metal-incorporated carbon-based catalysts. (C) 2020 Elsevier Ltd. All rights reserved.

Owing to the high abundance, good conductivity and excellent tolerance to harsh environment, carbon host materials have recently attracted considerable research interest in the fields of electrochemical hydrogen evolution reaction (HER). However, the deficiency of intrinsic active sites within the carbon host materials substantially gives rise to an inferior HER performance. In this work, atomically dispersed ruthenium active sites are deliberately introduced into the carbon host structure by controlled pyrolysis of Ru-doped ZIF-8. With atomic Ru sites on a unique whisker-like secondary microstructure and a favorable porous texture, the optimal product exhibits a high intrinsic activity as well as robust durability, which especially outperforms the Pt/C benchmarking in alkaline media. A combination of control experiments and theoretical calculations demonstrates that atomically dispersed Ru sites within the carbon host matrix serve as the dominant catalytically active sites, and remarkably optimize the free energy of water molecule dissociation during the Volmer step, thus boosting the HER performance.