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Electrochemical conversion of CO2 and water to valuable chemicals and fuels is one of the promising alternatives to replace fossil fuel-based processes in realizing a carbon-neutral cycle. For practical application of such technologies, suppressing hydrogen evolution reaction and facilitating the activation of stable CO2 molecules still remain major challenges. Furthermore, high production selectivity toward high-value chemicals such as ethylene, ethanol, and even n-propanol is also not easy task to achieve. To settle these challenges, deeper understanding on underlying basis of reactions such as how intermediate binding affinities can be engineered at catalyst surfaces need to be discussed. In this review, we briefly outline recent strategies to modulate the binding energies of key intermediates for CO2 reduction reactions, based on theoretical insights from density functional theory calculation studies. In addition, important design principles of catalysts and electrolytes are also provided, which would contribute to the development of highly active catalysts for CO2 electroreduction.

Research on electrocatalytic CO2 reduction reaction (CO2RR) has been growing rapidly owing to the urgent requirement of sustainable renewable energy. However, several obstacles hinder the application of liquid salt electrolytes in CO2RR, such as high costs, low concentrations of the product, and low purity due to the separation process of the product. Solid‐state electrolytes (SSEs) have been introduced as viable alternatives to liquid electrolytes and their salts to address this challenge. Here, we summarize the recently demonstrated studies and opportunities related to catholyte‐free CO2RR using SSEs. The recent studies are classified based on the product, including the CO2RR electrolyzer performance. Different SSEs are briefly discussed to highlight the new opportunities in CO2RR application. We also describe the basic operation parameter of the catholyte‐free CO2RR using SSE, which has been studied before as the key variable of the reactor. This review provides insights on minimizing the use of salt electrolytes for CO2RR and reveal opportunities for using this technique to improve the efficiency of CO2RR on a large scale. The exploration of utilizing solid‐state electrolytes (SSE) on a scale‐up production has been pursued to showcase their viability in integrating them into commercial CO2RR technology. [ABSTRACT FROM AUTHOR]

Molten salt-based electrolysis of CO 2 to a valuable carbon product is a promising method to overcome the excessive concentration of CO 2 in the atmosphere. Carbon nanotubes (CNTs) are one of the most favorable carbon nanomaterials. Recently, scientists have developed a CNT production method using molten salt-based CO 2 electrolysis and optimized reaction conditions to obtain desirable CNT products. However, to date, the production of single-walled CNTs (SWCNTs), as a type of CNTs with excellent chemical and physical properties, has not been realized. Here, we review the fundamental principles and process mechanisms of molten salt-based CO 2 electrolysis. In addition, we cover the key components for improving CNT production performance, such as cathode, anode, and electrolyte. Furthermore, we investigate the key strategies applied in chemical vapor deposition to produce commercial SWCNTs and suggest a perspective for SWCNT production from CO 2 based on material strategies. This paper provides deep insights into the CNT synthesis mechanism as well as a value-addition strategy through cost-efficient and environment-friendly CO 2 conversion processes. [Display omitted] • Recent progress of molten salt-based electrolysis of CO 2 to carbon nanotubes is reviewed. • Key components, such as cathode, anode, and electrolyte, are discussed. • Perspectives and future research of molten salt-based electrolysis of CO 2 to Carbon Nanotubes are proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 electroreduction on Pd-Mo mixed metal oxide catalyst varies on size and composition. • Pd-Mo MMO CO 2 electrocatalytic performance increases as Pd amount are increased. • Smaller sized PdMo possesses higher electrochemically active surface area. • Electronic structure mixing between Pd and Mo affects CO binding energy properties in Pd-Mo MMO. Electrochemical CO 2 reduction is considered a promising solution to mitigate the increasing CO 2 emissions in the atmosphere. Despite the promising potential of this process, highly active catalysts are needed to enable its efficient operation. Mixed metal oxide (MMO) materials can promote the formation of a dynamic interface between a metal and its oxidized form under applied potential, resulting in a unique interaction with the reaction intermediates. We synthesized a Pd–Mo MMO with controlled size and composition and examined the effect of these properties on CO 2 electroreduction. Electron microscopy images confirmed the homogeneous distribution of the synthesized Pd 7 Mo 1 on a ZIF-8-derived porous carbon support, with sizes of ∼1.3 and 4.5 nm for the samples annealed at 200 and 400 °C, respectively. As shown by density functional theory calculations and X-ray photoelectron spectroscopy, adding 12.5 % Mo altered the electronic structure of Pd, enhancing CO desorption, and reducing the potential needed for CO production by up to ∼0.2 V, corresponding to a ∼40 % higher partial CO current density compared to pure Pd. This work demonstrates a facile MMO synthesis enabling particle size and composition control, which will facilitate the development of highly active MMO-derived nanoalloy materials for CO 2 electroreduction. [ABSTRACT FROM AUTHOR]