No abstract

A world-wide growing concern relates to the rising levels of CO2 in the atmosphere that leads to devastating consequences for our environment. In addition to reducing emissions, one alternative strategy is the conversion of CO2 (via the CO2 Reduction Reaction, or CO2RR) into added-value chemicals, such as CO, HCOOH, C2H5OH, CH4, and more. Although this strategy is currently not economically feasible due to the high stability of the CO2 molecule, significant progress has been made to optimize this electrochemical conversion, especially in terms of finding a performing catalyst. In fact, many noble and non-noble metal-based systems have been investigated but achieving CO2 conversion with high faradaic efficiency (FE), high selectivity towards specific products (e.g., hydrocarbons), and maintaining long-term stability is still challenging. The situation is also aggravated by a concomitant hydrogen production reaction (HER), together with the cost and/or scarcity of some catalysts. This review aims to present, among the most recent studies, some of the best-performing catalysts for CO2RR. By discussing the reasons behind their performances, and relating them to their composition and structural features, some key qualities for an “optimal catalyst” can be defined, which, in turn, will help render the conversion of CO2 a practical, as well as economically feasible process.

The rising level of carbon dioxide (CO2), mainly a consequence of human activities, it is leading to devastating consequences to our environment and has raised concerns to the public opinion. To face this issue, governments are working to reduce the level of CO2 emissions, whilst the scientific community is focusing to implement the electrochemical conversion of the emitted CO2 (CO2RR) as source of added value chemicals.Due to the high stability of the CO2 molecule, to make its conversion practical, the process requires a suitable electro-catalyst. With the aim to understand the mechanism toward specific CO2RR product and thus increase selectivity, in this contribution, we have explored copper nanoparticles (Cu NPs), as one of the most promising catalyst for CO2 conversion, and investigated the reactivity as a function of selected experimental parameters. The results were rationalized via theoretical investigation, also discussed in the paper, to understand the mechanism behind their activity but, most importantly, to relate structure to selectivity. The Cu NPs, prepared via an unconventional sol-gel process, were shown to be pure, with homogeneous size and morphology, and were tested toward CO2RRs showing a total FE above 90%. The higher FE toward the production of C2H4 (up to 33% at an applied potential of -1.0 V) is one of the highest FE reported so far for Cu, without using expensive support. The final products were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM).

The rising level of carbon dioxide (CO2), mainly a consequence of human activities, it is leading to devastating consequences to our environment and has raised concerns to the public opinion. To face this issue, governments are working to reduce the level of CO2 emissions, whilst the scientific community is focusing to implement the electro-chemical conversion of the emitted CO2 (CO2RR) as source of added value chemicals. Due to the high stability of the CO2 molecule, to make its conversion practical, the process requires a suitable electro-catalyst. With the aim to understand the mechanism toward specific CO2RR product and thus increase selectivity, in this contribution, we have explored copper nanoparticles (Cu NPs), as one of the most promising catalyst for CO2 conversion, and investigated the reactivity as a function of selected experimental parameters. The results were rationalized via theoretical investigation, also discussed in the paper, to understand the mechanism behind their activity but, most importantly, to relate structure to selectivity. The Cu NPs, prepared via an unconventional sol-gel process, were shown to be pure, with homogeneous size and morphology, and were tested toward CO2RRs showing a total FE above 90%. The higher FE toward the production of C2H4 (up to 33% at an applied potential of -1.0 V) is one of the highest FE reported so far for Cu, without using expensive support. The final products were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM).