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1.
    
Developing highly active and stable electrocatalysts is essential for the large-scale production of hydrogen from alkaline water. In this work, Ag single atoms and nanoparticles co-decorated Co hydro(oxy)oxide (Ag SAs&NPs@CoO(O)H) is synthesized by a facile one-step approach. Notably, the overpotential of Ag SAs&NPs@CoO(O)H is 200 mV at current density of 50 mA cm−2 during oxygen evolution reaction (OER). Meanwhile, it can display the mass activity of 637.47 A g−1Ag under 300 mV, which is 212.49 times higher than that of commercial IrO2. Moreover, the assembled Pt/C // Ag SAs&NPs@CoO(O)H system only requires 1.9 V to reach an industrial current density of 1000 mA cm−2 in alkaline water electrolyzer and exhibits excellent stability at large current density of 1000 mA cm−2. Furthermore, in situ Raman spectroscopy analysis coupled with theoretical calculations reveals an novel active site switching mechanism is found on Ag SAs&NPs@CoO(O)H. Specifically, the O* preferentially generates on the Ag NPs and then switches toward the Co3+ site in CoO(O)H to produce OOH* and O2. Meanwhile, the Ag SAs in the lattice of CoO(O)H can exert an inhibitory force on the reconstruction process of CoOOH to Co(OH)2, resulting in excellent anti-dissolution stability.  相似文献   

2.
    
Heterostructured catalysts are hybrid materials that contain interfaces between their constituents formed through combinations of multiple solid‐state materials. The presence of multiple constituents institutes a synergistic effect that endows the catalyst with superior performance and appreciable potential in a diverse range of catalytic applications, including electrocatalytic and photocatalytic reduction of carbon dioxide. These promising catalysts can support a feasible method for large‐scale processing of valuable carbonaceous feedstock or fuel generation and alleviation of atmospheric carbon dioxide levels. Such technologies will serve as the much‐needed remedy for the global energy and environmental crisis. A broad spectrum of recently developed heterostructured catalysts pertaining to electrocatalytic and photocatalytic carbon dioxide reduction is evaluated. The insights included are of relevance to refresh fundamentals pertaining to the electron transfer processes leading to carbon dioxide reduction and the mechanistic reduction pathways yielding a possible multitude of carbonaceous products. Detailed discussions provide a rational understanding of how the hybrid and resultant properties from various combinations are useful in enhancing catalytic function. Lastly, the performance profiles of various catalyst structures together with modification strategies employed are of interest to highlight the current challenges to and directions for future catalyst development.  相似文献   

3.
    
Atomically dispersed metal-nitrogen-carbon catalysts have been extensively explored for various sustainable energy-related reactions. From a material perspective, these catalysts are likely to consist of a combination of single-atom, dual-atom and possibly even multi-atom sites. However, pinpointing their true active sites has remained a challenging task. In this study, a model catalyst is introduced, Co/CoMn-NC, featuring both Co single-atom sites and CoMn dual-atom sites on a nitrogen-doped carbon substrate. By employing a combination of X-ray adsorption spectroscopy and density functional theory calculations, the atomic configuration of Co/CoMn-NC has been determined. Density functional theory calculations are also used to unequivocally identify Co-atom within the CoMn dual-atom motif as the predominate active site of the Co/CoMn-NC model catalyst toward oxygen reduction reaction (ORR), which is further confirmed by in situ Raman spectroscopy. The cooperative interactions between Co single-atom sites and CoMn dual-atom sites can finely tune the d-band center and ameliorate the adsorption and desorption behaviors of the intermediates, thereby facilitating ORR kinetic. Overall, the study introduces a systematic strategy to elucidate the structure and the superiority of the model system and provides new insights into atomically dispersed multi-metal active sites, showcasing that enhanced catalytic performance extends beyond unified diatomic sites or monatomic sites.  相似文献   

4.
    
The recent advances in electrocatalysis for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR) are thoroughly reviewed. This comprehensive review focuses on the single‐atom catalysts (SACs) including Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sn, W, Bi, Ru, Rh, Pd, Ag, Ir, Pt, and Au with single‐metal sites or dual‐metal sites. The recent development of single‐atom electrocatalysts with novel configurations and compositions is documented. The understanding of the process–structure–property relationships is highlighted. For the SACs, their electrocatalytic performance and stability in fuel cells, zinc–air batteries, electrolyzers, CO2RR, and NRR are summarized. The challenges and perspectives in the emerging field of single‐atom electrocatalysis are discussed.  相似文献   

5.
    
Electrocatalytic nitrate reduction reaction (NO3RR) can convert nitrate contaminants into ammonia with higher added value. However, due to the NO3RR involving complex multi-electron reactions, there is an urgent need to develop efficient electrocatalysts. Herein, CoCu Janus nanoparticles loaded on Ti3C2Tx MXene (CoCu-Ti3C2Tx) is synthesized via the combination of molten salt etching and galvanic replacement strategy. The tandem catalysis of CoCu Janus NPs can maintain the balance between nitrogenous intermediates and active hydrogen (Hads). CoCu-Ti3C2Tx exhibits a high NH3 yield of 8.08 mg h−1 mgcat.−1 and a satisfactory Faradaic efficiency of 93.6% at −0.7 V versus reversible hydrogen electrode (RHE). The Zn-NO3− battery assembled with CoCu-Ti3C2Tx shows an excellent power density of 10.33 mW cm−2, an NH3 yield of 1.52 mg h−1 mgcat.−1 and a Faradaic efficiency of 95.3% at 10 mA cm−2, which enables the simultaneous elimination of nitrate pollutants, ammonia production, and energy supply. Moreover, a series of verification experiments and density functional theory calculation are combined to reveal the reaction path and tandem catalytic mechanism. This work not only provides a new inspiration for the design of tandem catalysts but also promotes the development of Zn-nitrate battery.  相似文献   

6.
    
Photocatalysis is considered to be a green and environment-friendly technology since it can convert solar energy into other types of chemical energies. Over the past several years, metal-organic frameworks (MOFs)-based photocatalysts have received remarkable research interest due to their unique morphology, high photocatalytic performance, good chemical stability, easy synthesis, and low cost. In this review, the synthetic strategies of developing MOFs-based photocatalysts are first introduced. Second, the recent progress in the fabrication of various types of MOFs composites photocatalysts is summarized. Third, the different applications including hydrogen evolution reaction, oxygen evolution reaction, overall water splitting, nitrogen reduction reaction, carbon dioxide reduction reaction as well as photodegradation of organic pollutants of MOFs-based photocatalysts are summed up. Finally, the challenges and some suggestions for the future development of MOFs- and their composites-based photocatalysts are also highlighted. It is expected that this report will help researchers to systematically devise and develop highly efficient photocatalysts based on MOFs and their composites.  相似文献   

7.
    
The electrocatalytic CO2 reduction reaction (CO2RR) has been considered a promising route toward carbon neutrality and renewable energy conversion. At present, most bismuth (Bi) based electrocatalysts are adopted to reduce CO2 to formate (HCOOH). However, the mechanism of different Bi nanostructures on the electrocatalytic performance requires more detailed exposition. Herein, a combined chemical replacement and electrochemical reduction process is reported to realize in situ morphology reconstruction from Bi@Bi2O3 nanodendrites (Bi@Bi2O3-NDs) to Bi nanoflowers (Bi-NFs). The Bi@Bi2O3-NDs are proven to undergo a two-step transformation process to form Bi-NFs, aided by Bi2O2CO3 as the intermediate in KHCO3 solution. Extensive surface reconstruction of Bi@Bi2O3-NDs renders the realization of tailored Bi-NFs electrocatalyst that maximize the number of exposed active sites and active component (Bi0), which is conducive to the adsorption and activation of CO2 and accelerated electron transfer process. The as-prepared Bi-NFs exhibit a Faradaic efficiency (FEformate) of 92.3% at −0.9 V versus RHE and a high partial current density of 28.5 mA cm−2 at −1.05 V versus RHE for the electroreduction of CO2 to HCOOH. Moreover, the reaction mechanism is comprehensively investigated by in situ Raman analysis, which confirms that *OCHO is a key intermediate for the formation of HCOOH.  相似文献   

8.
    
Transition metal chalcogenides are an important class of electrocatalysts with broad application prospects in alkaline oxygen evolution reactions. Many researchers are focusing on the in situ conversion of metal cations in catalysts, but have rarely considered the contribution of oxidation, leaching, and re-absorption of chalcogenides to the catalytic activity. Herein, multiple characterization approaches are used to monitor the evolution mechanism and origin CoTe@CoS-electrocatalyzed oxygen evolution reaction (OER) activity. The research results reveal that the electro-oxidative dissolution of Te and S on the electrode surface forms TeO32− and SO32−, which are adsorbed on the electrode surface. Moreover, TeO32− and SO32− species will further transform into TeO42− and SO42−. As expected, the extra addition of mixed tellurite and sulfate ions to the Co (OH)2 electrolyte produces a synergistic effect that can significantly boost OER activity. Selenites reveal the analogous effect, indicating that the adsorption of chalcogenates the electrode surface has a universal effect on improving OER performance. The findings of this work provide unique insights into the species conversion of catalytic materials and the mechanism of enhancing catalytic activity during OER processes.  相似文献   

9.
    
The production of atomically thin transition-metal dichalcogenides (TMDs) has been investigated through various top-to-down exfoliation methods, such as mechanical and chemical exfoliation, while large-scale chemical exfoliation is sluggish and needs over ten hours to achieve atomically thin TMDs. Herein, a new strategy is reported for exfoliating bulk MoS2 into two/three-layer flakes within tens of seconds through a mild electrochemical treatment. This exfoliation method is driven by a lateral inward oxidation reaction starting from the typical layer edge with a rapid depth penetration, whereby a stacked few-layer (two/three layers) structure is ultimately formed. This efficient reaction process is monitored based on an individual MoS2 on-chip device combined with in situ Raman and cross-sectional scanning transmission electron microscopy, and the uniformity of thickness is demonstrated. This preferentially initiated method can be also extended to produce few-layer MoSe2 and the selective extraction mechanism is assumed to be related to intrinsic layer-dependent energy band properties. Moreover, the special reassembled few-layer MoS2 possesses great performance as functional materials in electrocatalysis (127 mV overpotential for hydrogen evolution reaction) and surface-enhanced Raman spectroscopy (105 enhancement factor). These results illustrate the broad prospects of the reassembled few-layer MoS2 for optics, catalysis, and sensors.  相似文献   

10.
    
Pseudocapacitance‐induced electrochemical actuators (EC‐actuators) have attracted great attention in robots and artificial intelligence technologies. Despite major efforts to design such EC‐actuators, a molecular‐level understanding of the deformation mechanism is still lacking. Here, a reversible deformation of a freestanding MnO2/Ni bilayer film is demonstrated and in situ electrochemical atomic force microscopy, in situ Raman spectroscopy, and density functional theory simulation are used to study the origin of the deformation. The results show that the electrochemical actuation of the MnO2/Ni film is highly related with the redox pseudocapacitive behavior of MnO2 layer. Valence state variation of Mn element, shortening and lengthening of Mn? O bond, and insertion and extraction of Na+ ions, which all result from the redox pseudocapacitance of MnO2 during charging and discharging, eventually lead to the reversible contraction and expansion of MnO2 morphology. Such action counters with the nonactive Ni layer, finally inducing the reversible deformation of the MnO2/Ni bilayer film. It is believed that the study can provide useful guidance to design better EC‐actuators in the future.  相似文献   

11.
    
Bismuth sodium titanate (BNT)‐derived materials have seen a flurry of research interest in recent years because of the existence of extended strain under applied electric fields, surpassing that of lead zirconate titanate (PZT), the most commonly used piezoelectric. The underlying physical and chemical mechanisms responsible for such extraordinary strain levels in BNT are still poorly understood, as is the nature of the successive phase transitions. A comprehensive explanation is proposed here, combining the short‐range chemical and structural sensitivity of in situ Raman spectroscopy (under an applied electric field and temperature) with macroscopic electrical measurements. The results presented clarify the causes for the extended strain, as well as the peculiar temperature‐dependent properties encountered in this system. The underlying cause is determined to be mediated by the complex‐like bonding of the octahedra at the center of the perovskite: a loss of hybridization of the 6s2 bismuth lone pair interacting with the oxygen p‐orbitals occurs, which triggers both the field‐induced phase transition and the loss of macroscopic ferroelectric order at the depolarization temperature.  相似文献   

12.
拉曼光谱是一种分子指纹光谱,在物质成分识别和定量分析领域已得到广泛应用,近年来也逐渐应用于深海极端环境的原位探测。回顾了激光拉曼光谱技术的发展历程,介绍了国内外已经研发的深海激光拉曼光谱探测系统,并着重介绍了各系统在深海冷泉、热液等极端区域对喷口流体、沉积物孔隙水、自生碳酸盐岩、水合物等目标物的原位探测和应用,最后总结了限制拉曼光谱技术在深海取得更多应用的因素,可以为拉曼光谱技术未来的发展提供参考。  相似文献   

13.
    
Electrocatalytic reduction of NO2− to NH3 (NO2RR) presents a fascinating approach for simultaneously migrating NO2− pollutants and producing valuable NH3. In this study, single-atom Rh-alloyed copper (CuRh1) is explored as a highly active and selective catalyst toward the NO2RR. Combined theoretical calculations and in situ FTIR/EPR spectroscopic experiments uncover the synergistic effect of Rh1 and Cu to promote the NO2RR energetics of CuRh1 through a tandem catalysis pathway, in which Rh1 activates the preliminary adsorption and hydrogenation of NO2− (NO2− → *NO2 → *NOOH → *NO), while the generated *NO on Rh1 is then transferred on Cu substrate which promotes the rate-determining step of *NO → *NHO toward the NH3 synthesis. As a result, CuRh1 equipped in a flow cell presents an unprecedented NH3 yield rate of 2191.6 µmol h−1 cm−2 and NH3-Faradaic efficiency of 98.9% at a high current density of 322.5 mA cm−2, as well as long-term stability for 100 h electrolysis.  相似文献   

14.
    
The reduction of carbon dioxide (CO2) into chemical feedstock is drawing increasing attention as a prominent method of recycling atmospheric CO2. Although many studies have been devoted in designing an efficient catalyst for CO2 conversion with noble metals, low selectivity and high energy input still remain major hurdles. One possible solution is to use the combination of an earth‐abundant electrocatalyst with a photoelectrode powered by solar energy. Herein, for the first time, a p‐type silicon nanowire with nitrogen‐doped graphene quantum sheets (N‐GQSs) as heterogeneous electrocatalyst for selective CO production is demonstrated. The photoreduction of CO2 into CO is achieved at a potential of ?1.53 V versus Ag/Ag+, providing 0.15 mA cm?2 of current density, which is 130 mV higher than that of a p‐type Si nanowire decorated with well‐known Cu catalyst. The faradaic efficiency for CO is 95%, demonstrating significantly improved selectivity compared with that of bare planar Si. The density functional theory (DFT) calculations are performed, which suggest that pyridinic N acts as the active site and band alignment can be achieved for N‐GQSs larger than 3 nm. The demonstrated high efficiency of the catalytic system provides new insights for the development of nonprecious, environmentally benign CO2 utilization.  相似文献   

15.
利用磁控溅射方法在表面有SiO2层的Si基片上溅射Ta/NiFe薄膜,采用X射线光电子能谱(XPS)研究了SiO2/Ta界面以及Ta5Si3标准样品,并进行计算机谱图拟合分析.实验结果表明在制备态下在SiO2/Ta界面处发生了热力学上有利的化学反应:37Ta+15SiO2=5Ta5Si3+6Ta2O5,界面处形成更稳定的化合物新相Ta5Si3、Ta2O5.在采用Ta作阻挡层的ULSI铜互连结构中这些反应产物可能有利于对Cu扩散的阻挡.  相似文献   

16.
    
Beta-type gallium oxide (β-Ga2O3) is a new attractive material for optoelectronic devices. Different methods had been tried to grow high quality β-Ga2O3 crystals. In this work, crystal growth of Ga2O3 has been carried out by chemical vapor transport (CVT) method in a closed quartz tube using C as transport agent and sapphire wafer as seed. The CVT mass flux has been analyzed by theoretical calculations based on equilibrium thermodynamics and 1D diffusional mass transport. The crystal growth experimental results are in agreement with the theoretical predictions. Influence factors of Ga2O3 crystal growth, such as temperature distribution, amount of C as transport agent used, have also been discussed. Structural (XRD) and optical (Raman spectroscopy, photoluminescence spectrum) properties of the CVT-Ga2O3 crystal are presented.  相似文献   

17.
利用磁控溅射方法在表面有SiO2层的Si基片上溅射Ta/NiFe薄膜,采用X射线光电子能谱(XPS)研究了SiO2/Ta界面以及Ta5Si3标准样品,并进行计算机谱图拟合分析.实验结果表明在制备态下在SiO2/Ta界面处发生了热力学上有利的化学反应:37Ta+15SiO2=5Ta5Si3+6Ta2O5,界面处形成更稳定的化合物新相Ta5Si3、Ta2O5.在采用Ta作阻挡层的ULSI铜互连结构中这些反应产物可能有利于对Cu扩散的阻挡.  相似文献   

18.
The double perovskite oxide calcium erbium niobate, Ca2ErNbO6 (CEN) is synthesized by solid-state reaction technique. The Rietveld refinement of the room temperature X-ray diffraction pattern of the material shows that CEN is crystallized in the monoclinic P21/n crystal symmetry. Vibrational properties of the sample for P21/n symmetry are analysed using Raman and infrared spectroscopies. The dielectric relaxation and ac conductivity of CEN are investigated in the temperature range from 303 to 573 K and in the frequency range from 100 Hz to 1.1 MHz using impedance spectroscopy. Modified Cole–Cole equation is used to describe the relaxation phenomenon. The frequency dependent conductivity spectra follow the Jonscher power law. The values of Activation energy indicate that the dielectric relaxation and the conduction mechanism are due to adiabatic small polaron hopping of charge carriers. The complex impedance plane plot of the sample indicates the presence of both grain and grain-boundary effects and is analyzed by an electrical equivalent circuit consisting of resistances and constant-phase elements.  相似文献   

19.
    
Recently, vigorous progress is made in the selective and high-current reduction of carbon dioxide (CO2) to ethylene (C2H4) by using a flow cell. In most cases, however, the reduction is only achieved in strong alkaline electrolytes, which results in substantial deactivation of electrocatalysts due to the accumulation of precipitates. Here, porous Cu nanowires (NWs) is prepared with abundant atomic defects, which create a synergy with the pore-induced electric field to comprehensively tune the local microenvironment of the electrode surface, thus enabling efficient and stable C2H4 production from the CO2 reduction reaction (CO2RR) in neutral media. In particular, the enhanced electric field effect increases the local K+ concentration for the generation of *CO intermediates; while the atomic defects stabilize OH− and *CO, leading to high local pH and *CO coverage. Such synergy can provide a favorable local environment and high *CO coverage for significantly decreasing the energy barrier of the C─C coupling step. Consequently, a large partial C2H4 current density of 222.3 mA cm−2 with excellent stability is achieved in a neutral electrolyte. Altogether, this work paves new pathways to promote C2H4 production in the neutral CO2RR through multiple tuning of the local environment.  相似文献   

20.
    
Oxygen reduction reaction (ORR) is the core reaction of fuel cell/metal–air battery at the cathode, and it is of great significance to develop high-performance ORR catalyst. Generally speaking, ORR catalysts are classified according to the class of materials they use, which often makes it difficult for different types of catalysts to have a clear connection with some unified optimization mechanism and creates difficulties in designing improvement strategies. Here, this review proposes three major strategies that can affect the activity of ORR catalysts: designing morphology, defect control, and heteroatom doping. The core content of this review is to analyze the principles of various optimization strategies that affect the performance of catalysts individually or synergistically at the micro level. In addition, the problems and challenges still faced in the design of ORR catalysts are sorted out, and possible solutions are proposed. This review makes the research direction of ORR catalysts clearer, and provides theoretical support and new ideas for the design of high-efficiency electrocatalysts.  相似文献   

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