Photogenerated charge separation is one of the key factors determining the solar energy conversion efficiency in photocatalysis and photoelectrocatalysis. Fabrication of phase junction has been ...demonstrated to be an effective strategy to construct the internal electric field for the charge separation. Phase junction is essentially a heterojunction, but more common in semiconductor-based photoelectric conversion systems, because most semiconductors exhibit the polymorphous structures. Because of the similar crystal structure between the two phases, phase junctions are more easily formed. The application of phase junction in photocatalysis and photoelectrocatalysis, especially the anatase–rutile TiO2 and α–β Ga2O3 phase junction, are summarized in this Feature Article. The internal electrical field across the phase junction provides enough driving force for the improved charge separation, evidenced by the time and spatial resolved characterizations. We conclude with a summary and perspectives on the design and application of phase junction in solar energy conversion systems.
Power systems are exceedingly faced with extreme events such as natural disasters and deliberate attacks. In comparison, the underground natural gas system is considered less vulnerable to such ...extreme events. We consider that the overhead power grid can be hardened by replacing segments of electric power grid with underground natural gas pipelines as an energy transportation system to countereffect extreme events which can damage interdependent infrastructures severely. In this paper, an integrated electricity and natural gas transportation system planning algorithm is proposed for enhancing the power grid resilience in extreme conditions. A variable uncertainty set is developed to describe the interactions among power grid expansion states and extreme events. The proposed planning problem is formulated as a two-stage robust optimization problem. First, the influence of extreme events representing natural disasters is described by the proposed variable uncertainty set and the proposed robust model for the integrated planning is solved with the grid resilience represented by a set of constraints. Second, the investment decisions are evaluated iteratively using the conditional events. The integrated electricity and natural gas planning options are analyzed using the modified IEEE-RTS 1979 for enhancing the power grid resilience. The numerical results point out that the proposed integrated planning is an effective approach to improving the power grid resilience.
A coordinated operation of smart grid (SG) and intelligent transportation system (ITS) provides electric vehicle (EV) owners with a myriad of power and transportation network data for EV charging ...navigation. However, the optimal charging navigation would be a challenging task owing to the randomness of traffic conditions, charging prices and waiting time at EV charging station (EVCS). In this paper, we propose a deep reinforcement learning (DRL)-based EV charging navigation, aiming at minimizing the total travel time and the charging cost at EVCS. First, we utilize the deterministic shortest charging route model (DSCRM) to extract feature states out of collected stochastic data and then formulate EV charging navigation as a Markov Decision Process (MDP) with an unknown transition probability. The proposed DRL-based approach will approximate the solution, which can adaptively learn the optimal strategy without any prior knowledge of uncertainties. Case studies are carried out within a practical zone in Xi'an city, China. Numerous experimental results verity the effectiveness of the proposed approach and illustrate its adaptation to EV driver preferences. The coordination effect of SG and ITS on reducing the waiting time and the charging cost in EV charging navigations is also analyzed.
Lithium metal batteries (LMB) are recognized as the most promising high-energy-density energy storage devices. However, its large-scale commercial applications are seriously hampered by the poor ...cycling stability and potential safety issues. Solid electrolyte interphase (SEI) acts a dominant role in influencing the regulation of Li deposition and overall performance of LMBs, but the composition as well as the evolution of SEI remain quite elusive. Advanced characterization methods and operando monitoring techniques are urgently required. Herein, in this perspective, we first briefly introduce the development history of SEI research and the SEI formation mechanisms as well as the common known components of SEI. Then, we focus on several recent advanced technologies for SEI characterization and monitoring, and the corresponding study cases will be presented. In the end, perspectives including the future investigation directions, the in situ characterization methods, and the component-performance associated model are proposed. We believe that this timely review will help to give a comprehensive understanding on the up-to-date SEI characterization tools.
Electric power and transportation networks become increasingly coupled through electric vehicles (EV) charging station (EVCS) as the penetration of EVs continues to grow. In this paper, we propose a ...holistic framework to enhance the operation of coordinated electric power distribution network (PDN) and urban transportation network (UTN) via EV charging services. Under this framework, a bi-level model is formulated to optimally determine EVCS charging service fees (CSF) for guiding EV charging behaviors and minimizing the total social cost. At the upper level, PDN with wind power generation is formulated as a second-order cone problem (SOCP) where CSF is determined. Given the settings calculated at the upper level, the lower level problem is described as a traffic assignment problem (TAP) which is subject to the user equilibrium (UE) principle and captures the individual rationality of single EV owners in UTN. The uncertainties in wind power output and origin-destination (O-D) traffic demands are considered in the proposed model and a deep reinforcement learning (DRL)-based solution framework is developed to decouple and approximately solve the stochastic bi-level problem. Both gradient-based and gradient-free training algorithms are implemented in this paper and the respective results are compared. The case studies on a 5-node system, 24-node Sioux-Falls system and real-world Xi'an city in China are conducted to verify the effectiveness of the proposed model, which demonstrates the enhanced operation of coordinated PDN and UTN networks by reducing the traffic congestion and improving the integration of renewable energy.
Mercury detection remains an important task because of its high toxicity. Herein a new dual-signal probe based on a boric acid (BA)-functionalized lanthanide metal–organic framework (BA-Eu-MOF) was ...developed for the detection of Hg2+ and CH3Hg+ ions for the first time. The BA-Eu-MOF was synthesized by coordination of Eu3+ with 5-boronobezene-1, 3-dicarboxylic acid (5-bop) through a one-pot method. The 5-bop ligand not only acted as the “antenna” to sensitize the luminescence of Eu3+ but also provided reaction sites for Hg2+ and CH3Hg+. Owing to the electron-withdrawing effect of the BA group, the “antenna” effect of the ligand was passivating and the BA-Eu-MOF showed weak red emission in water. Upon addition of Hg2+ or CH3Hg+ into the system, a transmetalation reaction took place, i.e., BA groups were replaced by Hg2+ or CH3Hg+; therefore, the “antenna” effect of the ligand was triggered, leading to the enhancement of red emission. As Hg2+ or CH3Hg+ concentration increased, the red emission was gradually enhanced, and the color change was also observed with the naked eye under 365 nm ultraviolet light. Owing to the porous characteristics and the surface effect of the MOF, as well as the unique transmetalation reaction between the BA group and Hg2+ or CH3Hg+, the developed nanoprobe showed excellent characteristics for simultaneous detection of Hg2+ and CH3Hg+, such as simple preparation, convenient operation, “turn-on” signal output, high sensitivity, and selectivity. The unique features of the BA-Eu-MOF make it an attractive probe for monitoring Hg2+ and CH3Hg+.
It has been anticipated that learning from nature photosynthesis is a rational and effective way to develop artificial photosynthesis system, but it is still a great challenge. Here, we assembled a ...photoelectrocatalytic system by mimicking the functions of photosystem II (PSII) with BiVO4 semiconductor as a light harvester protected by a layered double hydroxide (NiFeLDH) as a hole storage layer, a partially oxidized graphene (pGO) as biomimetic tyrosine for charge transfer, and molecular Co cubane as oxygen evolution complex. The integrated system exhibited an unprecedentedly low onset potential (0.17 V) and a high photocurrent (4.45 mA cm–2), with a 2.0% solar to hydrogen efficiency. Spectroscopic studies revealed that this photoelectrocatalytic system exhibited superiority in charge separation and transfer by benefiting from mimicking the key functions of PSII. The success of the biomimetic strategy opened up new ways for the rational design and assembly of artificial photosynthesis systems for efficient solar-to-fuel conversion.
Photothermal therapy (PTT) is attracting increasing interest and becoming more widely used for skin cancer therapy in the clinic, as a result of its noninvasiveness and low systemic adverse effects. ...However, there is an urgent need to develop biocompatible PTT agents, which enable accurate imaging, monitoring, and diagnosis. Herein, a biocompatible Gd-integrated CuS nanotheranostic agent (Gd:CuS@BSA) was synthesized via a facile and environmentally friendly biomimetic strategy, using bovine serum albumin (BSA) as a biotemplate at physiological temperature. The as-prepared Gd:CuS@BSA nanoparticles (NPs) with ultrasmall sizes (ca. 9 nm) exhibited high photothermal conversion efficiency and good photostability under near-infrared (NIR) laser irradiation. With doped Gd species and strong tunable NIR absorbance, Gd:CuS@BSA NPs demonstrate prominent tumor-contrasted imaging performance both on the photoacoustic and magnetic resonance imaging modalities. The subsequent Gd:CuS@BSA-mediated PTT result shows high therapy efficacy as a result of their potent NIR absorption and high photothermal conversion efficiency. The immune response triggered by Gd:CuS@BSA-mediated PTT is preliminarily explored. In addition, toxicity studies in vitro and in vivo verify that Gd:CuS@BSA NPs qualify as biocompatible agents. A biodistribution study demonstrated that the NPs can undergo hepatic clearance from the body. This study highlights the practicality and versatility of albumin-mediated biomimetic mineralization of a nanotheranostic agent and also suggests that bioinspired Gd:CuS@BSA NPs possess promising imaging guidance and effective tumor ablation properties, with high spatial resolution and deep tissue penetration.
The high performance of a pseudocapacitor electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. We present a powerful two-step ...solution-based method for the fabrication of transition metal oxide core/shell nanostructure arrays on various conductive substrates. Demonstrated examples include Co3O4 or ZnO nanowire core and NiO nanoflake shells with a hierarchical and porous morphology. The “oriented attachment” and “self-assembly” crystal growth mechanisms are proposed to explain the formation of the NiO nanoflake shell. Supercapacitor electrodes based on the Co3O4/NiO nanowire arrays on 3D macroporous nickel foam are thoroughly characterized. The electrodes exhibit a high specific capacitance of 853 F/g at 2 A/g after 6000 cycles and an excellent cycling stability, owing to the unique porous core/shell nanowire array architecture, and a rational combination of two electrochemically active materials. Our growth approach offers a new technique for the design and synthesis of transition metal oxide or hydroxide hierarchical nanoarrays that are promising for electrochemical energy storage, catalysis, and gas sensing applications.
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