Well-defined hybrid Copper-based nanoreactors for electrocatalytic CO2 reduction

In the perspective of drastically reducing anthropogenic CO2 emissions and mitigating the effects of global warming, the electrochemical CO2 reduction reaction (CO2RR) powered by renewable sources and catalyzed by transition metal-based catalysts represents an attractive strategy to produce fuels and commodity chemicals. However, further improvement in the catalyst design is required to tackle the main bottlenecks that currently limit the performances of the state-of-the-art catalysts. Although several transition metal-based systems have been reported to catalyze CO2RR, catalyst durability and selectivity still represent major challenges to achieve an efficient CO2RR, mainly due to catalyst deactivation and to competitive Hydrogen evolution reaction (HER) and/or alternative pathways leading to multiple carbon-based products. The combination of molecular chemistry and heterogeneous catalysis has recently revealed to be an effective strategy to improve the overall efficiency and selectivity of the CO2RR process. In particular, the formation of hybrid catalysts based on the integration of organic molecules or reticular frameworks with heterogeneous metal or metal-oxide surfaces allowed to tune the stability of key reaction intermediates or the local microenvironment of the catalyst, resulting in a significant improvement of the CO2RR performances. In this contribution, we highlight a modular and versatile strategy to synthesize well-defined hybrid nanomaterials, based on the in situ growth of polymeric matrices around a well-defined metal nanoparticle core in a controlled manner. For instance, well-defined Cu2O nanocubes (NCs) are used as both templates and catalysts for an in situ polymerization based on a Cu-catalyzed azide–alkyne cycloaddition reaction (CuAAC) in the presence of the corresponding monomeric building blocks. This approach results in a series of hybrid nanoreactors with well-defined shape and size, which are active electrocatalysts for CO2 reduction in neutral-pH electrolyte. The composition of the molecular layer was found to be critical for the catalytic performances. The data herein presented provide a proof-of-concept of the potential offered by a molecular perspective towards a rational design of heterogeneous electrocatalysts

Copper-based hybrid nanomaterials for the electrocatalytic reduction of CO2

Global warming, worldwide energy crisis and the issues related to increasing levels of carbon dioxide (CO2) have prompted the research of new catalysts to transform CO2 back to fuels and value-added chemicals [1]. Copper (Cu)-based nanocatalysts have attracted increasing interest in CO2 reduction over the last decades, due to their unique capability to promote an electrochemical reduction of CO2 into multicarbon C2+ products. Nevertheless, an efficient Cu-catalyst is required to face the typical high overpotentials required for the process and the low selectivity, which results in obtaining a mixture of several products (C1-C3) [2]. Combining molecular with heterogeneous chemistry has revealed to be an efficient approach to improve the efficiency of the CO2RR processes [3]. In fact, the formation of hybrid materials combining heterogeneous Cu-based nanoreactors with organic or metal-organic frameworks allowed to tune stability of key reaction intermediates, enhancing selectivity towards some specific product [4]. In this work, we developed hybrid molecular-heterogeneous Cu-based nanomaterials for CO2RR, with the aim of tunning the selectivity of the nanostructured Cu catalysts by combining them with a purely organic molecularly defined polymer. The design of these systems is based on a novel strategy, whereby cuprous oxide (Cu2O) nanoparticles with a well-defined cubic geometry are used as both, templates and catalyst, for an in-situ polymerization reaction based on azide-alkyne ‘’click’’ reaction between the molecular building blocks. The catalytic performances of the hybrid nanomaterials were tested in a H-type electrochemical cell setup with an online gas-chromatographic quantification analysis (NMR was used for the liquid quantification analysis) and found to be efficient electrocatalysts for CO2RR obtaining a mixture of C1-C2 gaseous products (primarily CO, C2H4, CH4 in addition to H2) and C1-C3 liquids products (primarily C2H6O and CHOO-) in neutral pH electrolyte

FROM MOLECULES TO NANOSTRUCTURED MATERIALS: NOVEL OPPORTUNITIES FOR ELECTROCATALYTIC CO2 REDUCTION

The electrocatalytic CO2 reduction reaction (CO2RR) powered by renewable energy and promoted by transition metal catalysts, will play an important role in the global decarbonization process of the chemical industry, since represents a sustainable route for the production of value-added chemicals using CO2 as a feedstock. [1]-[2] However, despite the significant progress made in the field, selectivity, durability and intrinsic activity of the catalysts are still key challenges to achieve an efficient CO2RR. For organometallic molecular systems, characterized by a well-defined chemical environment of the active site, a rational tuning of the CO2RR efficiency and selectivity can be precisely controlled through a rational modification of the ligand scaffold. [3]-[5] Moreover, the encapsulation of molecularly defined active units into reticular frameworks was recently shown as an effective strategy to boost the CO2RR performances of molecular catalysts, but also to alter their redox behavior. [6] In recent years, the synergy between molecules and nanostructured materials has been proposed as a promising approach to design efficient heterogeneous catalysts for CO2 electroreduction. For instance, the presence of organic modifiers on metallic surfaces was found to tune the stability of key reaction intermediates or the local surface microenvironment, thus altering the product selectivity. [7]-[8] In this contribution, we will discuss novel strategies and approaches to form hybrid electrocatalysts based on the utilization of reticular or molecular chemistry as tools to steer the CO2RR selectivity and activity of transition metal-based nanostructured catalysts. The discussion will focus on providing a molecular perspective towards a rational design of heterogeneous catalysts