EnergyChem最新文献

Rechargeable zinc-air batteries (R-ZABs) are attractive for many essential energy storage applications – from portable electronics, electric vehicles to incorporation of renewable energy due to their high energy storage density, abundant raw materials, and inherent safety. However, alkaline electrolytes cause critical obstacles in realizing a long battery life. Thus, neutral electrolytes are attracting growing interest. However, the current understandings of R-ZABs in neutral/near-neutral electrolytes are far behind those in alkaline electrolytes. This review summarizes the latest research progress of neutral electrolytes used in R-ZABs, including aqueous inorganic and organic salt solutions, water-in-salt electrolytes, and quasi-solid electrolytes based on polymer hydrogels. Research efforts in improving the stability of Zn anodes in neutral electrolytes are also reviewed. Reaction mechanisms of oxygen reduction and evolution reactions in alkaline and neutral electrolytes are compared in the context of R-ZABs, together with a summary of potential oxygen electrocatalysts applicable in neutral conditions. Different device configurations are introduced. We further provide our perspectives on future research directions of R-ZABs with neutral electrolytes.

Hydrocarbon separations are crucial to the chemical industry for the production of valuable feedstocks. However, their structural and chemical similarities have proven daunting challenges to incumbent separation technologies, which are energy- and capital-intensive. Approaches capable of discerning and exploiting minute differences in isomeric hydrocarbons, in particular, may provide solutions to this problem. Metal-organic frameworks (MOFs) integrating the merits of tunable pore size at sub-angstrom scale and pore chemistry in confined spaces have presented promising prospects in adsorptive separation to recognize the minor differences in gas molecules via the judicious design and functionalization. In this Review, we explore the usage of MOFs for the underexplored adsorptive separation of hydrocarbons in the liquid/vapor phase, especially for C6 and C8 isomers. The in-depth insights into the structure-property relationship and the dominant mechanisms, including host-guest interaction modes for the effective adsorption of C6 and C8 hydrocarbons, are systematically discussed. Finally, the effectiveness and scope to translate such design strategies into other systems and the perspective on future development in MOFs for separation are provided.

Atomically dispersed metal catalysts (ADCs), particularly of noble metal, have unique catalytic properties such as maximized atom efficiency, high catalytic activity, and superior selectivity. In ADCs, the metal centers are in intimate contact with the support, hence, the support significantly affects the catalytic behavior of the ADCs by participating in reactions, either directly or indirectly. Therefore, for electrocatalytic reactions, thorough understanding of the function of the supports is required in designing effective ADCs with superior activity and stability. In this review, we summarize and discuss the functions of supports in several synthesis strategies and electrocatalytic reactions of atomically dispersed noble-metal catalysts. We outline various synthesis strategies, and identify a need for a suitable design of the support to stabilize the atom-dimension metal structure. Furthermore, we describe (electro)catalysis of ADCs, with focus on support-derived factors that affect the catalytic performance of the ADCs, such as strong metal-support interaction (SMSI), geometric effects of atom-dimension structure, local environment near metal centers, and chemical properties of supports. Finally, we identify current challenges and future prospects of functional supports in ADCs.

Single-atom catalysts (SACs) have attracted extensive attention because of their maximal atom utilization, unique electronic structure and high activity. Metal-organic frameworks (MOFs) could be used as perfect self-sacrificed precursors/templates for preparing SACs due to their uniformly distributed and spatially separated metal nodes and organic linkers as well as designable pore structures. Recently, numerous studies have been devoted to utilizing MOFs to prepare SACs through pyrolysis. Herein, this review summarizes the most recent strategies of turning selected MOFs into SACs, focusing on oxygen reduction reaction (ORR) catalysts. First, the inherent metal sites in MOFs are directly turned into single-atom sites via the high-temperature treatment with/without acid etching. Second, additional metal precursors are introduced into MOFs by various methods to further supplement active sites in the obtained SACs. Third, nonmetal heteroatom-rich (i.e., N, P and S) precursors are combined with MOFs to provide more coordination sites to anchor metal atoms. Finally, perspectives on future opportunities for selecting and designing MOFs as SAC precursors are also proposed.

Electrochemical water splitting in alkaline media provides a promising pathway for sustainable hydrogen production that is enssential for a future hydrogen economy. However, the slow reaction rate of hydrogen reaction in alkaline media, and unfavorable kinetics for oxygen evolution reaction have hindered the progress of water splitting technologies for clean hydrogen production. Considering the high price and scarce storage of noble metals which are known as the most effective catalysts for water splitting, it is urgently required to develop non-noble metals based alternatives with highly intrinsic acivity, low price and high tolerance to increase electrocatalytic efficiency and reduce the reaction overpotential from an economic perspective. In this review, we summarize recent research efforts in exploiting advanced transition metal based electrocatalysts with outstanding performance for water splitting catalysis, mainly including transition-metal-based chalcogenides, phosphides, nitrides and  carbides as well as single atom catalysts. First, we give a simple description of water splitting mechanism in alkaline media. Then we discuss the promising structural design of transition metal based electrocatalysts for enhancing water splitting, and disclose the underlying relationship between structure and electrocatalytic performance for water splitting with assistance of theoretical simulation. Finally, we provide our personal perspective to highlight the challenges and propose the opportunities for developing transition metal based electrocatalysts for water splitting in alkaline solution.

The appropriate band structure endows graphitic carbon nitride (g-C₃N₄) with benign redox ability and visible light response, resulting in its popularity in photocatalysis. Given the inferior solar-to-chemical (STC) energy conversion of single-component g-C₃N₄, loading cocatalysts is serviceable in advancing its photocatalytic activity. In particular, two-dimensional (2D) cocatalysts that could form 2D/2D heterojunctions with g-C₃N₄ stand out due to several advantages in which the large-area contact interface with g-C₃N₄ predominates. Herein, the basic information of g-C₃N₄ was first introduced. Then, representative 2D cocatalysts (e.g., graphene, graphdiyne, molybdenum disulfide, black phosphorus, and MXenes) used to strengthen the STC energy conversion of g-C₃N₄ were presented. Afterwards, the foremost achievements of g-C₃N₄ decorated with 2D cocatalysts in STC energy conversion were described in terms of photocatalytic hydrogen evolution, carbon dioxide reduction, hydrogen peroxide production, and nitrogen fixation. Finally, the future development and challenge of photocatalysts decorated with 2D cocatalysts were prospected. This paper could hopefully deepen the readers’ understanding of 2D cocatalysts in photocatalysis and attach importance to 2D cocatalysts described in this paper and many others not mentioned.

Aluminum (Al) is the most abundant metal element in earth crust, together with low cost and high safety. Al-ion batteries (AIBs) have been regarded as potential alternatives to lithium-ion batteries (LIBs) in large scale applications and attracted much attention in current days. In this review, recent developments of AIBs including the electrolyte exploration, electrode design and Al protection are summarized. Both aqueous and non-aqueous electrolytes exhibit important benefits for AIBs, especially ionic liquid electrolytes with high stripping/plating efficiency, which are preferentially discussed here. Furthermore, we highlight the design principles and electrochemical mechanism for carbons, metal compounds as well as new-type positive electrode materials for high-performance AIBs. Besides, we focus on the negative electrode protection with suitable coating layers to reduce dendrite formation and improve electrochemical activation of Al negative electrodes. The accessible characterization techniques that promote the development of AIBs are discussed. Finally, prospects and outlooks of AIBs towards theoretical investigations and practical applications are provided.

Aqueous zinc-metal batteries have gained widespread attention because of their high safety, large capacity, cost effectiveness, and environmental friendliness. However, zinc anodes have long encountered with dendrite formation, inferior cycle life and low coulombic efficiency, which severely hinder the practical application. Here, the latest advances of zinc metal anodes for aqueous zinc-metal batteries are reviewed. The merits of zinc metal anodes, the reaction mechanisms in different media, and the issues faced are firstly summarized. Then the prominent progresses of zinc anodes in aqueous media are highlighted, including electrolyte optimization, host construction, interface modification, anode structure design, and working model regulation. Finally, the remaining challenges of zinc anodes are fully discussed, and the future perspectives of pursing stable zinc metal anodes by integrating multi-strategies, conducting in situ study of zinc plating/stripping behavior, exploring advanced cathode materials, and developing smart devices are also provided.

C1 catalysis based on the transformation of methane, carbon monoxide, methanol and carbon dioxide offers great potential for the sustainable production of fuels and chemicals in response to the decrease of the energy consumption and plant maintenance. While the relatively inert nature of CH and CO bond (e.g., methane and carbon dioxide) and uncontrollable coupling of CC bond render the selective activation and controllable transformation of C1 molecules to high-value-added products challenging in C1 chemistry. Catalytic conversion of C1 energy molecules under mild conditions enables a better control of the selectivity of the desired products, however, which requires highly active catalysts to lower the reaction energy barriers. Besides designing efficient catalysts to promote C1 molecules conversion, employing electro-catalysis and photo-catalysis to circumvent the thermodynamic limitations is regarded as promising ways for C1 catalysis at low temperatures. Benefiting from the advanced technology for catalyst synthesis, reactor design, mechanism understanding, catalytic conversion of C1 molecules under mild conditions has made significant progress from 2010 to 2020. In this review, we summarized the typical catalytic processes and representative catalysts for transforming methane, carbon monoxide, methanol and carbon dioxide into high value-added chemicals with a reaction temperatures below 200 °C driven by thermo-catalysis, electro-catalysis, and photo-catalysis. Besides, a short perspective is offered to highlight possible future research directions towards C1 molecules conversion under mild conditions. It is expected to provide a useful reference for the readers to design better catalysts and reaction process for mild conversion of C1 molecules efficiently in future.

Lithium-ion batteries have become a staple in modern technology. Development of the next-generation batteries with higher energy storage capacity, light weight, and long lifetime is highly dependent on the advancement of novel materials utilized in each battery component. A recently emerging approach has been to utilize Covalent Organic Frameworks (COFs) to rationally design cathode, anode, and electrolyte materials for LIBs. COFs have many desirable properties, such as porosity, robust backbone, and customizable structure, for applications in LIBs. In this review, we discuss the electrochemical characterization of lithium ion batteries, general COF design principles, and examples of COF-based cathodes, anodes, and electrolytes to highlight the great potential and current obstacles in this rapidly developing field.