Abstract: Publication date: Available online 16 November 2018Source: Advances in CatalysisAuthor(s): Sharad Maheshwari, Yawei Li, Naveen Agrawal, Michael J. Janik Electrocatalysis facilitates conversion between electrical and chemical energy in fuel cells and electrolysis devices. Rational design of the electrocatalytic interface, including selection of electrode and electrolyte compositions and their optimal structure, requires establishing composition–structure–function relationships. Electronic structure calculations, most typically performed within the framework of density functional theory (DFT), help to develop these relationships by determining how elementary reaction energetics are impacted by electrocatalysis composition and structure. Though DFT methods can explain and predict catalytic behavior at the most fundamental level, they are challenged by difficulties in representing the length and time scales associated with processes at the dynamic electrode–electrolyte interface. In this chapter, we review the approaches used to approximate this interface with DFT for modeling electrocatalytic processes. We first review the challenges associated with modeling this interface, motivating an overview of the various approaches to model solvent and interface electrification. A more detailed emphasis is given to approaches to model the elementary kinetics of the inner sphere electron/ion transfer reactions that dictate activity and selectivity for processes occurring at solid electrode–liquid electrolyte interfaces.
Abstract: Publication date: Available online 13 November 2018Source: Advances in CatalysisAuthor(s): Chengyi Dai, Anfeng Zhang, Chunshan Song, Xinwen Guo Metals and zeolites are two important types of catalysts and widely used in oxidation–reduction and acid-catalyzed reactions, respectively. In recent years, zeolite-encapsulated metal catalysts have attracted great interest due to their excellent performance in metal–acid synergistic catalysis, selectivity to desired product, anti-leaching, and anti-sintering of metal. This review highlights the synthesis strategies for solid and hollow zeolite-encapsulated metal catalysts, such as ion-exchange, “ship-in-a-bottle,” hydrothermal crystallization, dry gel conversion, and posttreatment method, and their activity, selectivity, and stability in different reactions including hydrogenation, oxidation, reforming, coupling, reforming, hydroxylation, and degradation. The synthesis and advantages of hollow zeolite-encapsulated metal catalysts in various reactions are highlighted.
Abstract: Publication date: Available online 6 November 2018Source: Advances in CatalysisAuthor(s): Matteo Monai, Michele Melchionna, Paolo Fornasiero Catalysts are making our world more sustainable day by day. But how sustainable are catalysts themselves' In this contribution we will give a perspective overview of the progress in dematerializing catalysts, i.e., in using less (critical) materials to deliver the same (or better) level of functionality. This may be accomplished in many ways: improving the catalyst performance and durability by gaining insights in reaction, activation, and deactivation mechanisms; lowering the amount of critical or harmful catalytic components, e.g., by finding cheaper, more abundant, and sustainable substitutes; and making catalysts production and disposal processes more sustainable, e.g., by recycling. Material science and nanotechnology are two essential actors in this process, providing the tools to understand and optimize catalytic materials and processes, and to assess the environmental and toxicological impact of nanomaterials.
Abstract: Publication date: Available online 25 October 2018Source: Advances in CatalysisAuthor(s): Hai Wang, Liang Wang, Shenxian He, Feng-Shou Xiao The nanoporous catalysts with advantages of high surface areas and abundant nanoporosity have been widely used in heterogeneous catalytic processes, but their catalytic performances are generally lower than those of the corresponding homogeneous catalysts due to distinguishable exposed active sites and molecular diffusion. Recent results show that molecular diffusion strongly influences catalytic performances. Therefore, adjusting the molecular diffusion in the nanoporous catalysts is an efficient route for catalytic enhancement of heterogeneous catalysts. In this chapter, recent developments are briefly summarized on rational adjustment of molecular diffusion in the heterogeneous nanoporous catalysts, including the use of hierarchical zeolites for fast mass transfer, active sites such as metal and metal oxide nanoparticles fixed inside nanoporous crystals such as zeolites and MOFs for shape-selective diffusion, and employment of nanoporous polymer-based catalysts for controlling the catalyst wettability, where the relationship between molecular diffusion and catalytic properties is particularly emphasized. Finally, the perspectives and challenges for the adjustment of molecular diffusion in the heterogeneous catalysts such as sustainable preparation of hierarchical zeolites and introduction of functionalized groups in the nanoporous catalysts are discussed.
Abstract: Publication date: Available online 24 October 2018Source: Advances in CatalysisAuthor(s): Michele Aresta, Francesco Nocito, Angela Dibenedetto Carbon dioxide can be used as building block for chemicals and materials or source of carbon for fuels. The former application, if implemented at the correct scale, may boost the sustainability of the chemical industry. The latter is more relevant to the energy sector and requires cheap hydrogen from water or renewables for the hydrogenation of the cumulene. Both applications can, thus, render services to our society even if at different times and intensity. In this chapter, an analysis of possibilities is carried out, considering chemicals that have a market higher or close to 1 Mt/year, highlighting the pros and cons and which aspects (catalyst and process) must be further developed in order to have a successful exploitation of the technology. The integration of catalysis and biotechnology is discussed as a route to the utilization of large volumes of CO2. Letting Nature convert CO2 and using biomass in catalytic processes can be a win–win option in some cases.
Abstract: Publication date: Available online 16 October 2018Source: Advances in CatalysisAuthor(s): Seval Gunduz, Dhruba J. Deka, Umit S. Ozkan Solid oxide electrolysis cells (SOECs) for electrochemical splitting of H2O and CO2 have attracted significant attention as a promising technology to efficiently store surplus renewable energy in the form of valuable chemicals and fuels. An SOEC does not only convert electrical energy into chemical energy but also offers a route to reduce CO2 emissions. Simultaneous electrolysis of H2O and CO2 is possible in an SOEC to form synthesis gas, which is a raw material for the production of chemicals via the Fischer–Tropsch synthesis process. Compared to low-temperature electrolysis, high-temperature electrolysis in a solid oxide cell is advantageous because of lower overpotential loss, easier activation of reactants, and usage of cheaper transition metal catalysts as electrode materials. Significant amount of research has been done on developing suitable electrode materials for such electrolysis operations. While initial works mostly involved the state-of-the-art Ni-YSZ cermet cathode, alternative materials such as perovskite oxides have gained importance in recent years. In this chapter, we will provide a review of various cathode materials studied for H2O, CO2, and CO2 + H2O coelectrolysis, and discuss the associated degradation issues. It is important to understand how CO2 and H2O interact with electrode surfaces to enable a rational design of cathode materials. A discussion is included about the previous studies performed on understanding the fundamental phenomena involved in such interactions, reaction mechanisms, and pathways. In addition, a perspective on possible future research directions in the realm of high-temperature electrolysis is provided.
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