The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications i...

http://pubs.acs.org/doi/pdfplus/10.1021/acs.chemrev.5b00482

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

Photoreduction of CO2 into sustainable and green solar fuels is generally believed to be an appealing solution to simultaneously overcome both environmental problems and energy crisis. The low selectivity of challenging multi-electron CO2 photoreduction reactions makes it one of the holy grails in heterogeneous photocatalysis. This Review highlights the important roles of cocatalysts in selective photocatalytic CO2 reduction into solar fuels using semiconductor catalysts. A special emphasis in this review is placed on the key role, design considerations and modification strategies of cocatalysts for CO2 photoreduction. Various cocatalysts, such as the biomimetic, metal-based, metal-free, and multifunctional ones, and their selectivity for CO2 photoreduction are summarized and discussed, along with the recent advances in this area. This Review provides useful information for the design of highly selective cocatalysts for photo(electro)reduction and electroreduction of CO2 and complements the existing reviews on various semiconductor photocatalysts.

Cocatalysts for Selective Photoreduction of CO2 into Solar Fuels.

The CO2 electroreduction reaction (CO2RR) to fuels and feedstocks is an attractive route to close the anthropogenic carbon cycle and store renewable energy. The generation of more reduced chemicals, especially multicarbon oxygenate and hydrocarbon products (C2+) with higher energy densities, is highly desirable for industrial applications. However, selective conversion of CO2 to C2+ suffers from a high overpotential, a low reaction rate and low selectivity, and the process is extremely sensitive to the catalyst structure and electrolyte. Here we discuss strategies to achieve high C2+ selectivity through rational design of the catalyst and electrolyte. Current state-of-the-art catalysts, including Cu and Cu–bimetallic catalysts, as well as some alternative materials, are considered. The importance of taking into consideration the dynamic evolution of the catalyst structure and composition are highlighted, focusing on findings extracted from in situ and operando characterizations. Additional theoretical insight into the reaction mechanisms underlying the improved C2+ selectivity of specific catalyst geometries and compositions in synergy with a well-chosen electrolyte are also provided. The electrochemical reduction of carbon dioxide to fuels and feedstocks has received increased attention over the past few years. In this Review, Roldan Cuenya and co-workers discuss strategies to achieve high selectivity towards multicarbon products via rational catalyst and electrolyte design.

Rational catalyst and electrolyte design for CO2 electroreduction towards multicarbon products

The gradually increased concentration of carbon dioxide (CO2 ) in the atmosphere has been recognized as the primary culprit for the rise of the global mean temperature. In recent years, development of routes for highly efficient conversion of CO2 has received much attention. This Review describes recent progress on the design and synthesis of solid-state catalysts for the electrochemical reduction of CO2 . The significance of this catalytic conversion is presented, followed by the general parameters for CO2 electroreduction and a summary of the reaction apparatus. We also discuss various types of solid catalysts based on their CO2 conversion mechanisms. We summarize the crucial factors (particle size, surface structure, composition, etc.) determining the performance for electroreduction.

Nanostructured Materials for Heterogeneous Electrocatalytic CO2 Reduction and their Related Reaction Mechanisms

The use of electricity instead of stoichiometric amounts of oxidizers or reducing agents in synthesis is very appealing for economic and ecological reasons, and represents a major driving force for research efforts in this area. To use electron transfer at the electrode for a successful transformation in organic synthesis, the intermediate radical (cation/anion) has to be stabilized. Its combination with other approaches in organic chemistry or concepts of contemporary synthesis allows the establishment of powerful synthetic methods. The aim in the 21st Century will be to use as little fossil carbon as possible and, for this reason, the use of renewable sources is becoming increasingly important. The direct conversion of renewables, which have previously mainly been incinerated, is of increasing interest. This Review surveys many of the recent seminal important developments which will determine the future of this dynamic emerging field.

Modern Electrochemical Aspects for the Synthesis of Value-Added Organic Products.

The catalytic, electrocatalytic, or photocatalytic conversion of CO2 into useful chemicals in high yield for industrial applications has so far proven difficult. Herein, we present our work on the electrochemical reduction of CO2 in seawater using a boron-doped diamond (BDD) electrode under ambient conditions to produce formaldehyde. This method overcomes the usual limitation of the low yield of higher-order products, and also reduces the generation of H2 . In comparison with other electrode materials, BDD electrodes have a wide potential window and high electrochemical stability, and, moreover, exhibit very high Faradaic efficiency (74%) for the production of formaldehyde, using either methanol, aqueous NaCl, or seawater as the electrolyte. The high Faradaic efficiency is attributed to the sp(3)-bonded carbon of the BDD. Our results have wide ranging implications for the efficient and cost-effective conversion of CO2.

High-yield electrochemical production of formaldehyde from CO2 and seawater.

PROBLEM TO BE SOLVED: To provide a method for manufacturing formaldehyde in high efficiency and high selectivity by using a simple method and equipment under temperate conditions of normal temperature and normal pressure or vicinities thereof.SOLUTION: Formaldehyde is generated within a liquid medium consisting of an electrolyte-containing aqueous solution (e.g., sea water, etc.), an organic solution including an alcohol as an organic compound, or an aqueous organic solution, etc. by bubbling COwithin the electrolytic solution and electrolytically reducing COby using an electroconductive diamond electrode, preferably a boron-doped diamond (BDD) electrode.

Ozaki Takuya

Papers

High-yield electrochemical production of formaldehyde from CO2 and seawater.

Method for manufacturing formaldehyde