Single-atom catalysts not only maximize metal atom efficiency, they also display properties that are considerably different to their more conventional nanoparticle equivalents, making them a ...promising family of materials to investigate. Herein we developed a general host-guest strategy to fabricate various metal single-atom catalysts on nitrogen-doped carbon (M
/CN, M = Pt, Ir, Pd, Ru, Mo, Ga, Cu, Ni, Mn). The iridium variant Ir
/CN electrocatalyses the formic acid oxidation reaction with a mass activity of 12.9 Formula: see text whereas an Ir/C nanoparticle catalyst is almost inert (~4.8 × 10
Formula: see text). The activity of Ir
/CN is also 16 and 19 times greater than those of Pd/C and Pt/C, respectively. Furthermore, Ir
/CN displays high tolerance to CO poisoning. First-principle density functional theory reveals that the properties of Ir
/CN stem from the spatial isolation of iridium sites and from the modified electronic structure of iridium with respect to a conventional nanoparticle catalyst.
A hollow multishell structure (HoMS) is an assembly of multiple shells with voids between the individual shells. Accessible through nanopores, these voids represent separate reaction environments in ...the same assembly, such that HoMSs have unique properties that are applicable to diverse fields. These applications have mostly exploited the large specific surface area, high loading capacity and/or buffering effect of HoMSs, benefiting the mass/energy transmission and effective surface area. In comparison, the temporal-spatial ordering of reactions, as well as the dynamic smart behaviour of HoMSs, have been less explored but are also emphasized in this Perspective. We first describe the synthesis of HoMSs and the thermodynamic and kinetic aspects of their formation. We then consider the composition and structural functionalization of each shell within a HoMS and then highlight how these enable applications based on temporal-spatial ordering and dynamic smart behaviour.
Isolated single atomic site catalysts have attracted great interest due to their remarkable catalytic properties. Because of their high surface energy, single atoms are highly mobile and tend to form ...aggregate during synthetic and catalytic processes. Therefore, it is a significant challenge to fabricate isolated single atomic site catalysts with good stability. Herein, a gentle method to stabilize single atomic site metal by constructing defects on the surface of supports is presented. As a proof of concept, single atomic site Au supported on defective TiO2 nanosheets is prepared and it is discovered that (1) the surface defects on TiO2 nanosheets can effectively stabilize Au single atomic sites through forming the Ti–Au–Ti structure; and (2) the Ti–Au–Ti structure can also promote the catalytic properties through reducing the energy barrier and relieving the competitive adsorption on isolated Au atomic sites. It is believed that this work paves a way to design stable and active single atomic site catalysts on oxide supports.
Single atomic sites of Au are supported on defective TiO2 nanosheets and it is discovered that the surface defects on TiO2 nanosheets can effectively stabilize Au single atomic sites through forming a Ti–Au–Ti structure, and this Ti–Au–Ti structure can also promote the catalytic properties through reducing the energy barrier and relieving the competitive adsorption on isolated Au atomic sites.
Lead halide perovskite solar cells with the high efficiencies typically use high-temperature processed TiO2 as the electron transporting layers (ETLs). Here, we demonstrate that low-temperature ...solution-processed nanocrystalline SnO2 can be an excellent alternative ETL material for efficient perovskite solar cells. Our best-performing planar cell using such a SnO2 ETL has achieved an average efficiency of 16.02%, obtained from efficiencies measured from both reverse and forward voltage scans. The outstanding performance of SnO2 ETLs is attributed to the excellent properties of nanocrystalline SnO2 films, such as good antireflection, suitable band edge positions, and high electron mobility. The simple low-temperature process is compatible with the roll-to-roll manufacturing of low-cost perovskite solar cells on flexible substrates.
A novel and general method is proposed to construct three‐dimensional graphene/metal oxide nanoparticle hybrids. For the first time, it is demonstrated that this graphene‐based composite with open ...pore structures can be used as the high‐performance capacitive deionization (CDI) electrode materials, which outperform currently reported materials. This work will offer a promising way to develop highly effective CDI electrode materials.
Tungsten‐based catalysts are promising candidates to generate hydrogen effectively. In this work, a single‐W‐atom catalyst supported on metal–organic framework (MOF)‐derived N‐doped carbon (W‐SAC) ...for efficient electrochemical hydrogen evolution reaction (HER), with high activity and excellent stability is reported. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy analysis indicate the atomic dispersion of the W species, and reveal that the W1N1C3 moiety may be the favored local structure for the W species. The W‐SAC exhibits a low overpotential of 85 mV at a current density of 10 mA cm−2 and a small Tafel slope of 53 mV dec−1, in 0.1 m KOH solution. The HER activity of the W‐SAC is almost equal to that of commercial Pt/C. Density functional theory (DFT) calculation suggests that the unique structure of the W1N1C3 moiety plays an important role in enhancing the HER performance. This work gives new insights into the investigation of efficient and practical W‐based HER catalysts.
A single‐tungsten‐atom catalyst supported on metal–organic framework‐derived N‐doped carbon is reported. The catalyst demonstrates a high activity and excellent stability for efficient electrochemical hydrogen evolution.
The highly efficient electrochemical hydrogen evolution reaction (HER) provides a promising pathway to resolve energy and environment problems. An electrocatalyst was designed with single Mo atoms ...(Mo‐SAs) supported on N‐doped carbon having outstanding HER performance. The structure of the catalyst was probed by aberration‐corrected scanning transmission electron microscopy (AC‐STEM) and X‐ray absorption fine structure (XAFS) spectroscopy, indicating the formation of Mo‐SAs anchored with one nitrogen atom and two carbon atoms (Mo1N1C2). Importantly, the Mo1N1C2 catalyst displayed much more excellent activity compared with Mo2C and MoN, and better stability than commercial Pt/C. Density functional theory (DFT) calculation revealed that the unique structure of Mo1N1C2 moiety played a crucial effect to improve the HER performance. This work opens up new opportunities for the preparation and application of highly active and stable Mo‐based HER catalysts.
Single Mo atoms dispersed on N‐doped carbon was prepared as a catalyst. It showed high catalytic activity and stability for the hydrogen evolution reaction (HER), and its structure was characterized by electronic microscopy and XAFS measurements. The unique catalytic properties for HER were investigated by DFT calculations.
Hollow multi-shelled structures (HoMS) have made significant strides across a wide spectrum of scientific investigations since the inception of the sequential templating approach (STA) in 2009, ...revealing distinctive temporal-spatial ordering properties. The recent establishment of a mathematical model for STA has not only demystified the formation of concentration waves within the STA process but also extended its relevance to gentler solution-based systems, thereby broadening the HoMS landscape. Herein, focusing on photoelectric applications, this review first summarizes the unique temporal-spatial ordering features of HoMS. Subsequentially, the greatly enhanced properties of light capture and absorption, exciton separation, and transfer are deeply discussed. Finally, we conclude with a perspective on the potential challenges and burgeoning opportunities that lie ahead in the advancement of HoMS development.
Hollow multishelled structures (HoMSs) have gained numerous achievements in broad scientific research fields. In the past decade, the rapid developments of synthetic methods and advanced ...characterization technologies have enriched HoMS family with abundant chemical compositions and geometric structures. In addition, the control in phase structure and surface structure of HoMSs have also been reported in recent years. With great efforts devoted to controlling the compositional and structural characteristics, such as shell composition, shell number, shell thickness, and intershell space, HoMSs have displayed their intrinsic temporal–spatial nature and proven to be fruitful in optimizing mass transport, storage, and release. This review first summarizes the compositional and structural control of HoMSs in three levels, that is, building subunits, assembled functional shells, and HoMSs. Subsequentially, the essential influence of composition and structure on mass transport, storage, and release is deeply discussed by highlighting the application of HoMSs in energy storage, catalysis, electromagnetic wave absorption, and drug delivery. Finally, the challenges and opportunities in the future development of HoMSs are forecasted.
Hollow multishelled structures (HoMSs) have gained numerous achievements in broad applications. The composition and structure control in the subunits, shells and HoMSs as well as performance control of HoMSs are summarized in this review, which demonstrates the essential effect of compositions and structures on performance properties of HoMSs and helps to guide HoMSs design targeted to specific application requirements.
The Shunyi (SY) earth fissures originated due to groundwater pumping and have caused severe damage to the Beijing Capital International Airport (BCIA) and other infrastructure in Beijing, China. They ...are distributed along the pre-existing NE-SW trending normal Shunyi-Liangxiang (SL) fault zone, with 1–30 cm vertical offsets. Previous studies of this long-term ground displacement have concluded that a subsidence bowl has formed on the footwall (northwestern side) of the SL fault in the BCIA. However, based on our observations, the relative subsidence occurred exclusively on the southeastern side, behaving like the activation of the SL fault. This complex deformation pattern has led to the formation mechanism of the SY earth fissures remaining unclear. In this study, two groups of numerical simulations based on the geological and hydrogeological settings of the SY earth fissures were performed. In Scenario I, the pumping load was on the footwall, whereas in Scenario II, the pumping load was on the hanging wall. Our results show that there are always two areas in the faulted model that have undergone pumping-induced subsidence. The first subsidence area indicates that the actual regional subsidence bowl occurred extensively around the pumping well. This subsidence was blocked by the pre-existing normal fault zone. The second subsidence area is localized and occurred abruptly in the hanging wall adjacent to the fault zone regardless of the effect of the position of the pumping load. This localized differential subsidence, representing the secondary surface faulting, was accompanied by earth fissure formation due to concentration of the surface shear strain. These simulation results agree with the actual land deformation across the SY earth fissures. Furthermore, our results suggest that both the formation location and deformation pattern of the SY earth fissures were dependent upon the characteristics of the pre-existing SL fault zone. This is mainly attributed to the fact that the fault zone has a lower resistance than the surrounding materials. Our findings reveal the formation mechanism of the SY earth fissures and provide a new understanding of pumping-induced earth fissures in other faulted areas.
•The Shunyi earth fissures originated due to pumping and are controlled by a pre-existing normal fault.•The deformation pattern across the Shunyi earth fissures is complex.•Shear and horizontal strains are concentrated in the vicinity of the pre-existing fault zone during drawdown.•Pumping triggered secondary surface faulting.•The lower resistance of the pre-existing normal fault induced the formation of the earth fissures.
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