Project summary:

Converting solar energy into clean energy, such as hydrogen energy, is admitted as one of the most effective approaches to resolve the energy problem, in this regard, photocatalysis being considered as a spearhead of such an approach. The major hurdle that needs to be overcome in this area however is the recombination of photogenerated electrons and holes. In this regard, the combination of MXenes with various semiconductor photocatalysts led to a marked increase in photoactivity. In this view, through this project, we aim to develop new photocatalytic systems that comprise the use of i-MXene-semiconductor composites for hydrogen production by photocatalytic water splitting reaction. The project approach is to develop operational powder composites based on i-MXene and stable and active semiconductor photocatalyst materials, which should be able in the end to perform easily the hydrogen evolution reaction on their surface. The originality of this project stands in the enrichment of current knowledge in the field of hydrogen evolution reaction by photocatalytic water splitting. It has to be underlined that, currently there is no studies published in the literature comprising the use i-MXene as co-catalysts for this application.

Project objectives:

The main MAXIM’s goal is to develop new photocatalytic systems based on 2D layered i-MXenes for photocatalytic water splitting. The derived specific objectives of the MAXIM project are:
O1. Design and optimization of the synthesis of active photocatalytic systems based on i-MXenes.
O2. Achievement of high apparent quantum efficiencies for hydrogen production through water splitting.
O3. Insights in the reaction mechanism based on the correlations of material characteristics with their photocatalytic performances. A special focus will be devoted to the use of in situ studies, paying particular attention to the study of the mechanism of hydrogen production through water splitting and electrons movement, as well as to the regeneration of active sites.

Estimated results:

The proposal aims to expand the existing knowledge in the field of hydrogen production through photocatalytic water splitting reaction by introducing new approaches to improve the development of new MXene-based composite able to directly convert the light into energy stored in chemicals, a hot topic of these days. Thus, the estimated results of the project are:
- Methods for the preparation of photocatalytic composites based on i-MXenes;
- Thermal and oxidative stability of the photocatalytic composites based on i-MXenes;
- Morphology of surfaces and textural properties;
- Optimal synthesis method and reproducibility of the synthesis method;
- Photocatalytic performance and conditions for efficient realization of the water splitting reaction with hydrogen production;
- Optical, vibrational and structural properties of i-MXenes-based composites;
- The key characteristics of i-MXenes-based composites that influence photoactivity;
- The mechanism of the water splitting reaction on i-MXenes-based composites;
- Publication of at least two articles in high-impact journals (greater than 6);
- Participation in international conferences (at least two participations / year);
- 1 patent application.

Project coordinator: Dr. Ștefan Neațu - Senior researcher II

Members:

Dr. Florentina Neațu - Senior researcher I

Dr. Mihaela Mirela Trandafir - Senior researcher III

Dr. Anca Coman - Senior researcher

Drd. Maria-Iuliana Chirică - Assistant researcher

Dr. Andrei Cristian Kuncser - Senior researcher III

Drd. Alexandra Corina Iacoban - Assistant researcher

Stage I

Within this stage, the following research activities were foreseen: 1) Synthesis of i-MXenes starting from i-MAX phases; 2) Synthesis of composites based on i-MXene. Ensuring the stability of these composites; 3) Characterization of MXene-based composites by investigating thermal, oxidative, morphological and textural properties. Determination of structural properties; 4) Verification of the photoactivity of i-MXene-based composites. Ensuring good photocatalytic results by adding small amounts of noble metal (Pt, Pd, etc.); and 5) Dissemination of results.

Starting from experimental data present in the specialized literature, in this first stage of the project several i-MAX phases of the type Mo_2/3Y_1/3AlC and (W_2/3Sc_1/3)₂AlC were prepared. Starting from these parent i-MAX phases, we moved on to the synthesis of i-MXenes of the Mo_1.33C type, materials that were further used to obtain i-MXene/TiO₂ composites by applying a hydrothermal approach. The composites were characterized using several types of characterization techniques, and their photocatalytic performance was verified in the production of H₂ through the water splitting reaction. The best performing composite generates a hydrogen production rate of over 500 µmol g^–1 h^–1, which is among the highest values reported in the literature on MXene-based photocatalysts. The obtained results open new opportunities in the preparation of highly active materials for the production of H₂ through the photocatalytic water splitting reaction.

The objectives were fully met. The detailed results can be found in the scientific report submitted to the Contracting Authority.

Stage II

During this stage, the following research activities were scheduled: 1) Enhancing the synthesis techniques of i-MXene-based composites and conducting their characterization; 2) Enhancing the conditions of the reaction; 3) Assessing the composites under optimal conditions in the photocatalytic water splitting process; and 4) Disseminating the results.

After completing the activities of Stage II of the MAXIM project, the critical synthesis parameters of the most promising i-MXene-based composites were identified. In this way, the best synthesis methods and reaction conditions were found so that the photocatalytic water splitting reaction could happen with high values of apparent quantum efficiency. The composites were characterised using advanced analysis techniques, and the photocatalytic reactions were carried out under optimal conditions.

The objectives have been fully achieved. The comprehensive findings are available in the scientific report that has been submitted to the Contracting Authority.

1. “Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures”, Hussein O. Badr, Varun Natu, Ștefan Neațu,* Florentina Neațu, Andrei Kuncser, Arpad M. Rostas, Matthew Racey, Michel W. Barsoum,* Mihaela Florea*, Matter 2023, 6, 2853–2869; 10.1016/j.matt.2023.05.026;
2. “A comparative overview of MXenes and metal oxides in clean energy production through photocatalysis”, Mahesh M. Nair, Alexandra C. Iacoban, Florentina Neațu, Mihaela Florea,* Ștefan Neațu*, Journal of Materials Chemistry A 2023, 11, 12559–12592; 10.1039/D2TA08983A;

Ștefan NEAȚU, Doctor in the field of Chemistry

Senior researcher II

E-mail: stefan.neatu@infim.ro

Department: Laboratory of Catalytic Materials and Catalysis