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Mo doping and Se vacancy engineering synergistically boost electrocatalytic water oxidation.

Electronic and architecture engineering is realized via doping an ultralow amount of Ir into NiMoO4-ZIF hammers to achieve outstanding electrocatalytic OER performance.

Wind and solar photovoltaic (PV) power form vital parts of the energy transition toward renewable energy systems. The rapid development of these two renewables represents an enormous infrastructure construction task including both power generation and its associated electrical grid systems, which will generate demand for metal resources. However, most research on material demands has focused on their power generation systems (wind turbines and PV panels), and few have studied the associated electrical grid systems. Here, we estimate the global metal demands for electrical grid systems associated with wind and utility-scale PV power by 2050, using dynamic material flow analysis based on International Energy Agency's energy scenarios and the typical engineering parameters of transmission grids. Results show that the associated electrical grids require large quantities of metals: 27-81 Mt of copper cumulatively, followed by 20-67 Mt of steel and 11-31 Mt of aluminum. Electrical grids built for solar PV have the largest metal demand, followed by offshore and onshore wind. Power cables are the most metal-consuming electrical components compared to substations and transformers. We also discuss the decommissioning issue of electrical grids and their recovery potential. This study would deepen the understanding of the nexus between renewable energy, grid infrastructure, and metal resources.

Oxygen evolution reactions (OERs) are regarded as the rate-determining step of electrocatalytic overall water splitting, which endow OER electrocatalysts with the advantages of high activity, low cost, good conductivity, and excellent stability. Herein, a facile H

Single-atom site catalysts (SACs) provide an ideal platform to identify the active centers, explore the catalytic mechanism, and establish the structure-property relationships, and thus have attracted increasing interests for electrocatalytic energy conversion. Substantial endeavors have been devoted to the construction of carbon-supported SACs, and their progress have been comprehensively reviewed. Compared with carbon-supported SACs, transition metal compounds (TMCs)-supported SACs are still in their infancy in the field of electrocatalysis. However, they have also aroused ever-increasing attention for driving electrocatalytic water splitting, and emerged as an indispensable class of SACs in recent years, predominately owing to their inherently structural features, such as rich anchoring sites, surface defects, and lattice vacancy. Herein, in this review, we have systematically summarized the recent advances of a variety of TMC supported SACs toward electrocatalytic water splitting. The advanced characterization techniques and theoretical analyses for identifying and monitoring the atomic structure of SACs are firstly manifested. Subsequently, the anchoring and stabilization mechanisms for TMC supported SACs are also highlighted. Thereafter, the advances of TMC supported SACs for driving water electrolysis are systematically unraveled.

In this manuscript, multiple patterns of slow-fast motion in an accelerating viscoelastic beam model are analyzed from both analytic and numerical view. Based on the modified averaging method, the static solutions of amplitude response equations are obtained. The stability analysis about the zero solution of the averaged equations shows that the zero solution loses its stability through pitchfork bifurcation and the small eigenvalue indicates the existence of strong transient. The numerical bifurcation diagrams and time histories of the fast sub-system verify the results obtained from the averaging process, especially strong transient effects in the vicinity of small amplitude branch. Based on these, two cases of low frequency excitation are considered. When the period of the slow excitation is much larger than the critical time for the fast sub-system to converge to the intermediate branch, the transitions related to pitchfork bifurcation are always periodic. While, if the period of the slow excitation possesses the same magnitude as that of the critical time, transitions between the small amplitude branch and intermediate amplitude can present both regular and irregular manners, which results in complex dynamic buckling regimes. Thus, multiple patterns of slow-fast motion including “periodic bursts with quasi-periodic spiking”, “torus/short transient” mixed mode oscillations, periodic “pitchfork/long transient” mixed mode oscillations, amplitude-modulated oscillations, as well as irregular mixed mode oscillations, are analyzed from numerical view.

In this manuscript, slow-fast motions in a two degrees of freedom model under slow parametric and fast external excitations are analyzed using analytical and numerical methods. By expressing the state variables as the sums of slowly varying average and fast oscillations, the averaged equations which govern the slow dynamics for different magnitudes of external amplitude are obtained. For the averaged equations, analyzation about the equilibria and the corresponding stability shows that, the averaged slow manifolds constitute a pitchfork structure. Meanwhile, the harmonic balancing method is used to compute the slowly varying envelopes of the fast oscillations. On the other hand, bifurcation diagrams of the fast sub-system show structures in accordance with the pitchfork obtained from averaged equations as well as the amplitude curves computed by harmonic balancing method. Two forms of relative location between the folds of cycle on the handle and pitchfork bifurcation point are presented. Based on these, concerning on the slow-fast flow, two patterns of transition behavior between the handle and the upper (lower) branch of pitchfork namely “pitchfork/pitchfork” and “fold/pitchfork” types are analyzed, which indicate the dynamic buckling behaviors. Particularly, discussion about the influence of external excitation shows that, for case of near-resonant external frequency, increasing the amplitude of external excitation will change the local structures as well as the quantitative properties of the pitchfork, but holistic form of pitchfork type is a topological invariant.

Electrocatalytic water oxidation is a rate-determining step in the water splitting process; however, its efficiency is significantly hampered by the limitations of cost-effective electrocatalysts. Here, an advanced Co(OH)

For dynamic systems with multiple time scales, its long-term behaviors usually present as mixed mode oscillations (MMOs). The formation of MMOs is closely related to the fast transitions evoked by the bifurcations of the fast sub-system. Up till now, most of the results reported in deterministic systems focus on periodic MMOs, namely the holistic structure of waveform shows periodicity, no matter whether the slow manifolds that the fast–slow flow follows are periodic or not. Moreover, since the motion of the fast–slow flow is modulated by the critical manifolds, qualitative influences of transient behaviors on the holistic structure of MMOs are less concerned. While in this paper, three patterns of aperiodic MMOs are analyzed based on a three-dimensional nonautonomous system under slow parametric excitation. According to the types of manifolds among which the fast transitions take place, these MMOs can be named as aperiodic “cycle-chaos-cycle” MMOs, aperiodic “cycle-chaos-cycle” MMOs with additional chaotic bursters, and aperiodic “chaos-cycle-point” MMOs. By combining the fast–slow analysis on certain time intervals and the probe into the transient chaos near boundary crisis, generation mechanisms of these MMOs are investigated. Our results show that the relative location between the boundary crisis value and the minimum of slow variable will qualitatively change the pattern of large amplitude oscillations (LAOs); thus, the composition of bursters can be decided by the intensity of transient chaos. On the other hand, the small amplitude oscillations (SAOs) evoked by interior crisis may contain inner structures related to bifurcation delay and sharding phenomenon. Particularly, interior crisis can lead to merging phenomena of chaotic attractors. Thus, when the chaotic LAOs stages are over, the fast–slow flow can transit to upper or lower branch in a irregular way, which results in the uncertain locations of SAOs.

The Nb2O5-TiO2 catalyst system was synthesized via sol-gel method and investigated for adsorption/catalytic combustion of toxic 1,2-dichloroethane (DCE), which was usually recognized as a representative of various chlorinated and brominated VOCs pollutants. The research results of structure-performance relationship revealed that binary Nb2O5-TiO2 were amorphous and mesoporous materials with pore diameter mainly in the range of 2–10 nm, and Nb and Ti elements were uniformly dispersed. The interaction between Nb2O5 and TiO2 coupled with the molar ratio of Nb/Ti improved the physicochemical properties of Nb2O5-TiO2. Moreover, Nb2O5-TiO2 exhibited higher catalytic activity for DCE combustion than single Nb2O5 or TiO2. Especially, the 2Nb1Ti catalyst (Nb/Ti = 2:1, molar ratio) displayed the highest activity, over which 90% conversion of DCE could be achieved at 295 °C. These results were related to that the interaction effect between Nb2O5 and TiO2 improved acidity and oxidizing properties, and the materials had large surface area, all of which were favorable for adsorbing DCE at relatively low temperatures (below 93 °C) on Nb2O5-TiO2 and then improving catalytic combustion performance at lower reaction temperatures than Nb2O5 or TiO2. Besides, during the long-term continuous reaction, even though partial deactivation was observed for this catalyst, it could be suppressed at elevated temperature.

Quantitative phase imaging technology has become an important technology for imaging phase objects such as cells in virtue of the advantages of non-destructive, non-invasive and high accuracy. More importantly, the phase of a cell is closely related to its internal structure and component. In this paper, according to the morphological and optical characteristics of typical leukocytes, the approximate models of different kinds of cells were firstly established to obtain the corresponding phases. Then, digital image edge operators such as gradient, gradient module and Laplace were used to detect the phase maps. Subsequently with the phase detection images of the cell, its feature information, such as the morphology and the refractive index change can be analyzed. Simulation results suggested that the edge operators are sensitive to the morphology, the interface of each medium and component of the cell. Therefore, the edge detection method of phase image can be used for cell’s classification recognition and preliminary determination of internal structure

Nb2O5 based solid superacids (Nb2O5-MOx, M = Ti, W, Zr, Si, Al and Ca, respectively) were synthesized by sol-gel method using citric acid as the cross-linking agent, and then were investigated for catalytic combustion of 1,2-dichloroethane (abbreviation: DCE), one of the typical examples for chlorinated VOCs pollutants. The research results of the structure-performance relationship show that mesopore and amorphous state structure are formed for Nb2O5-MOx, and the metal elements are highly dispersed, which contribute to enhancing the metal-metal interaction and modifying the physicochemical properties of the catalysts. The order for the inherent catalytic activity is: Nb2O5-WO3＞Nb2O5-ZrO2＞Nb2O5-TiO2＞Nb2O5-SiO2＞Nb2O5-Al2O3＞Nb2O5＞Nb2O5-CaO. There exists synergistic catalytic effect: the mesopore and surface acidity facilitate the adsorption, activation and destruction of the C Cl bond in the reactants to form HCl and byproduct C2H3Cl (or carbocation intermediate), and then the redox sites promote deep oxidation of the byproduct/intermediate to convert to CO2 and H2O. Especially, the Nb2O5-TiO2 catalyst represents the highest apparent catalytic degradation activity. It also represents good thermal stability and durability for DCE destruction as well as good resistance to water vapor.

Clean energy technologies are emerging as a major contributor to the total energy supply. Some metals play irreplaceable roles in these technologies. The supply risk of metals used in clean energy technologies is gradually increasing. Hence, it is necessary to investigate the supply risks of these metals worldwide. In this study, a comprehensive assessment is conducted to quantify the supply risks of critical metals. The production of the metals is imbalanced worldwide. China, Russia, the United States, Canada, and Australia dominate the supply of these metals. China has the largest supply risk, and the main risk contribution is linked to mining governance and policy, which suggests that strengthening government regulations is necessary. The supply risks in the United States, Russia, and Canada are moderate, and most risks are associated with geologic availability and recycling restrictions. Al, Cu, Fe, Pb and Ag displayed high risks linked to geologic availability and recycling restrictions. Pd, B, Sb, W, Re, Ge and Ga exhibited high risks related to mining governance and policy and environmental sustainability. Difficult exploration processes and highly sensitivity market supplies increased the supply risk. This study provides an important reference for the strategic application of the metals in clean energy technologies in the future.

Recycling rare metal tantalum from waste tantalum capacitors (WTCs) is significant to alleviate the shortage of tantalum resource. However, environmental problems will be caused if the organic materials from WTCs are improperly disposed. This study presented a promising vacuum pyrolysis technology to recycle the organic materials from WTCs. The organics removal rate could reach 94.32 wt% according to TG results. The optimal parameters were determined as 425 °C, 50 Pa and 30 min on the basis of response surface methodology (RSM). The oil yield and residual rate was 18.09 wt% and 74.94 wt%, respectively. All pyrolysis products can be recycled through a reasonable route. Besides, to deeply understand the pyrolysis process, the pyrolysis mechanism was also proposed based on the product and free radical theory. This paper provides an efficient process for recycling the organic material from WTCs, which can facilitate the following tantalum recovery.

Waste printed circuit boards (WPCBs) are valuable urban ore for recycling. Many efforts have been done to recover resources from basal boards of WPCB. In addition to basal boards, WPCBs contain many electronic components. However, the recycling technology for electronic components has been poorly developed. This study proposed an integrated and environment-friendly technology for recycling waste tantalum capacitors (WTCs) of WPCBs. Firstly, the WTCs were treated by argon pyrolysis to decompose mold resin. The pyrolysis temperature of 550 °C and holding time for 30 min were considered as the optimal parameters. Then, the pyrolysis residues were performed by crush and magnetic separation to recover nickel-iron terminals. Finally, chloride metallurgy (CM) was used to recover rare metal tantalum (Ta). The Ta recovery rate could reach 92.87 ± 0.36%. The optimal parameters were determined as temperature of 493 °C, adding FeCl 2 ·4H 2 O of 53 wt% and holding time for 150 min based on the response surface methodology (RSM). This study exploits an efficient approach for recycling WTCs and provides a reference for future industrial application.

Tantalum capacitors (TCs) are widely used in electronic appliances. The rapid replacement of electronic products results in generating large amounts of waste TCs (WTCs). WTCs, rich in valuable tantalum, are considered as high quality tantalum resources for recycling. However, environmental pollution will be caused if the organics of WTCs were not properly disposed. Therefore, effectively recycling the organics of WTCs is significant for recovering the valuable parts. This study proposed an argon (Ar) pyrolysis process to recycle the organics from WTCs. The organic decomposition kinetic was first analyzed by thermogravimetry. The results showed that the organics were decomposed in two major steps and the average activation energy was calculated to 234kJ/mol. Then, the suitable pyrolysis parameters were determined as 550°C, 30min and 100ml/min. The organics were effectively decomposed and converted to oils (mainly contained phenol homologs and benzene homologs) and gases (some hydrocarbon). These pyrolysis products could be reutilized as energy sources. Moreover, based on the products and bond energy theory, the pyrolysis mechanisms of the organics were also discussed. Finally, a reasonable technological process for products utilization was presented. This study contributes to the efficient recycling the organics before valuable material recovery from WTCs.

Recycling e-waste has been a significant topic for environmental protection and also for resource recovery. Waste tantalum capacitors (WTCs), widely existing in discarded small appliances, are rich in high quality tantalum (Ta) resources. However, recovering Ta from WTCs is difficult due to the tightly covered mold resin. This study proposes an efficient and environmentally friendly process using supercritical water (SCW) to decompose the organics and recover Ta from WTCs. Two methods of SCW were studied: SCW depolymerization (SCWD) and SCW oxidation (SCWO). The results indicated that the mold resin (packing) of WTCs were effectively decomposed by SCW treatments. The organic decomposition efficiency in SCWD was lower than that in SCWO. The optimal parameters for SCWD and SCWO were, respectively, considered to be 425 °C, 25 MPa, and 120 min and 400 °C, 25 MPa, and 90 min, adding a 10% volume ratio of H2O2. After SCWO treatment, Ta electrodes were directly recovered, and the purity of Ta could reach 93.18%....

Based on the idea of slow-fast dynamics, two tapping modes are investigated in the Atomic Force Microscope (AFM) model with Lennard-Jones force and slow-fast base motion. According to the approximation derived from Taylor expansion in the vicinity of static equilibrium of the linearized system, we give a prediction about harmonic responses of the fast sub-system (FSS). Then a truncated version of harmonic balancing method (HBM) is combined with the Floquet theory to give the distribution and stability of the harmonic responses, which indicates the contact and non-contact modes dominated by cycle manifolds. By directly integrating the FSS, the numerical bifurcation diagrams and the frequency spectrums corresponding to the periodic solutions are obtained to verify the results given by the half-analytic process. Moreover, distribution of basins of attraction shows that, when the tri-stability is destroyed by fold bifurcation of cycle, due to the highly fragmented fractal structures in basins, transition between different mode manifolds may present an weak irregular way. On the other hand, when the slow excitation is introduced, the regular and irregular “cycle-cycle” type mixed mode oscillations (MMOs) triggered by “fold of cycle/fold of cycle” hysteresis can be observed, which results in two tapping mode, .i.e., the slow tapping mode and the “compound of contact/snap tapping” mode. Besides that, our results show that, for the AFM under slow and near-resonant excitation, the beneficial effects of constant contact mode and snap tapping mode can be utilized.