MEtal NAnoClusters for Electrocatalytic CO2 conversion

Project Information

MENACE-CO2

Grant agreement ID: 894270

DOI

10.3030/894270

Project closed

EC signature date 26 March 2020

Start date 1 September 2021

End date 12 May 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 172 932,48

EU contribution

€ 172 932,48

Coordinated by

UNIVERSITAT POLITECNICA DE VALENCIA
Spain

Periodic Reporting for period 1 - MENACE-CO2 (MEtal NAnoClusters for Electrocatalytic CO2 conversion)

Reporting period: 2021-09-01 to 2023-08-31

Summary of the context and overall objectives of the project

This project aims to address the development of advanced catalysts based on metal nanoclusters (MNCs) for efficiently converting CO2 through electrochemical processes (EC CO2RR). The significance lies in tackling environmental challenges by enhancing the activity and selectivity of CO2 conversion, potentially contributing to reducing greenhouse gas emissions. This project aims to address the development of advanced catalysts based on metal nanoclusters (MNCs) for efficiently converting CO2 through electrochemical processes (EC CO2RR). The significance lies in tackling environmental challenges by enhancing the activity and selectivity of CO2 conversion, potentially contributing to reducing greenhouse gas emissions. The specific objectives include: 1) Achieving fundamental understanding of MNCs as catalysts for the electroreduction of CO2, such as insight into size and composition dependence and an in-depth understanding of the catalytic mechanisms through correlation of behavior and structure (WP1). 2) To tune their catalytic performance, by surface modification of MNCs with molecular metal oxides to enhance the adsorption of CO2 (WP2). 3) To immobilize catalysts into nanocarbon materials, improving catalyst stability and performance due to the synergy between the support substrate and supported catalyst (WP3).

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The primary scientific aim of this WP was to elucidate the structure-activity relationships of thiolate-protected metal nanoclusters (MNCs) as catalysts for the electrochemical CO2 reduction reaction (EC CO2RR). To achieve this, two families of gold clusters, Au25(SR)18 and Au144(SR)60 (each of them with distinct staple motifs and sizes) doped with Ag or Cu have been explored to elucidate the interplay between composition and catalytic performance. The scientific quality of the results is demonstrated since a paper has been accepted (after revisions that are currently in progress) in ACS Catalysis.
Main Scientific Achievements:
• Development of Bimetallic Nanoclusters.
• Enhanced Selectivity: Cu-doped Au144(SR)60 demonstrates the highest activity for CO production at –0.8 VRHE due to partial ligand depletion and staple bending, which stabilizes the *CO intermediate.
• Mechanistic Insights: The study elucidates the dynamic role of ligands in stabilizing intermediates during EC CO2RR and the importance of ligand stability.

The primary scientific aim of this WP was to enhance the CO2 adsorption properties of MNCs. To this end, the preparation of nanocomposites combining MNCs and molecular metal oxides (i.e. polyoxometalates, POMs) was planned. The initial plan was to evaluate the composites as catalysts for EC CO2RR. However, our findings indicated that the clusters aggregated into nanoparticles during ligand exchange reactions with POMs. Given that the application of metal nanoparticles for EC CO2RR is already well-documented,further testing of these metal nanoparticles for this purpose was deemed unnecessary. Consequently, we redirected our efforts to investigate the electrochemical behavior of these materials as modified electrodes in a symmetrical supercapacitor configuration. This was a collaboration with Prof. Pedro Gomez-Romero at ICN2 and the results have been published (Nanomaterials 2023, 13(15), 2241).

The last objective of the project was to study the effect of nanocarbon supports on the catalytic performance of MNCs. To this end, MNC/nanocarbon hybrid materials have been prepared and fully characterized.
Two preparation approaches were used: 1) physisorption methods (deposition of pre-made MNCs on nanocarbons ultrasonically mixing), and 2) chemisorption methods (a covalent route) to efficiently anchor MNCs on nanocarbons. We have studied the utilization of graphene doped with different heteroatoms (P, N, and S). S has a special interest since it can stabilize clusters through strong S-Au covalent bond interaction. Au25(SR)18@graphene materials were characterized by electron microscopy, XRD, XPS, and UV-vis. Then, the resulting composite materials were characterized and tested as catalysts for EC CO2RR and compared with the performance of Au25(SR)18@carbon black (being carbon black the traditional support for this type of catalytic measurements). The results are being compiled in a manuscript that will be soon submitted.
Main Scientific Achievements:
• Synthesis of composite materials combining clusters with heteroatom-doped graphene.
• Enhanced Electrocatalytic Performance: The study demonstrated that doping graphene with S significantly improves the stability and performance of the Au25(SR)18 catalysts in CO2RR.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

This project represents significant advancements in the field of catalysis for the electrochemical CO2 reduction reaction (EC CO2RR) through the development and characterization of thiolate-protected metal nanoclusters (MNCs). Several key areas of progress are highlighted:

Elucidation of Structure-Activity Relationships:
By exploring two families of gold clusters, Au25(SR)18 and Au144(SR)60, doped with silver (Ag) or copper (Cu), the research has provided novel insights into how the size, composition, and structural motifs of MNCs affect their catalytic performance.
The study has advanced the understanding of the interplay between composition and catalytic activity, particularly in stabilizing reaction intermediates, which is crucial for optimizing catalyst design.
The synthesis of Cu- and Ag-doped Au nanoclusters represents an innovative approach to enhance catalytic properties. This has led to the identification of Cu-doped Au144(SR)60 as having superior activity for CO production, attributed to ligand effects that stabilize the *CO intermediate.
The scientific quality of these findings is validated by the acceptance of a paper in the prestigious journal ACS Catalysis, indicating significant recognition in the field.

Enhancement of CO2 Adsorption Properties:
Initial efforts to enhance CO2 adsorption involved creating nanocomposites of MNCs with molecular metal oxides (POMs). While traditional testing for EC CO2RR was found unnecessary due to nanoparticle aggregation, this pivot led to the investigation of these materials in supercapacitors.
This redirection has opened new avenues for the application of MNCs, with results published in Nanomaterials, showcasing the versatility and potential of these composites in energy storage technologies.

Impact of Nanocarbon Supports:
The project successfully synthesized and characterized MNC/nanocarbon hybrid materials, employing both physisorption and chemisorption methods. The focus on heteroatom-doped graphene, particularly with sulfur (S), has demonstrated notable improvements in catalyst stability and performance.
S-doped graphene significantly enhances the stability and performance of Au25(SR)18 catalysts in CO2RR, achieving a CO faradaic efficiency of 50% at specific voltages, comparable to traditional carbon black supports.
Electrochemical Impedance Spectroscopy (EIS) revealed lower diffusion resistance and higher activity in these materials, attributed to their open structure and accessible surface area. Stability tests further suggest that graphene-supported catalysts exhibit higher durability due to d-π bonding interactions.
The findings are being compiled into a manuscript for submission, which will contribute further to the body of knowledge and highlight the advancements achieved through this research.