Photoinduced ultrafast carriers and thermal effects within metasurfaces for light-driven catalysis

Informazioni relative al progetto

PATHWAYS

ID dell’accordo di sovvenzione: 101153856

DOI

10.3030/101153856

Progetto chiuso

Data della firma CE 12 Aprile 2024

Data di avvio 16 Maggio 2024

Data di completamento 15 Maggio 2026

Finanziato da

• Marie Skłodowska-Curie Actions (MSCA)

Costo totale

Nessun dato

Contributo UE

€ 175 737,12

Coordinato da

POLITECNICO DI MILANO
Italy

Periodic Reporting for period 2 - PATHWAYS (Photoinduced ultrafast carriers and thermal effects within metasurfaces for light-driven catalysis)

Periodo di rendicontazione: 2025-05-16 al 2026-05-15

Sintesi del contesto e degli obiettivi generali del progetto

Catalysis lies at the heart of modern industrial chemistry. It enables the production of more than 85% of chemical goods essential to our daily life, from plastics and pharmaceutical products to fertilisers, and contributes to trillions of euros in annual revenue. Yet, the chemical processes behind these products remain highly energy-intensive. They often require extreme operating conditions (pressures over 100 atm, temperatures above 400 °C), and are typically fed by fossil fuel combustion. As a result, the chemical industry is one of the world’s largest energy consumers (~2.5% of global use), and emits close to 1.5% of global greenhouse gases (around one gigaton per year). Greening, intensifying and enhancing selectivity of these large-scale processes by powering them under milder conditions is a critical challenge for climate neutrality and industrial sustainability.

One promising way towards this urgent transformation is plasmonic photocatalysis, an emerging approach that uses light and metallic nanostructures to drive chemical reactions. These nanoscale, ‘plasmonic’, materials concentrate light into extremely small volumes, offering a local environment where reactions can proceed by light excitations at pressures and temperatures far below those that typify traditional reactors. By modifying how energy is delivered to the reaction sites, they can change rates and open new, otherwise inaccessible reactivity channels.

Despite exceptional promise, current plasmonic photocatalysis methods face two major limitations: the inability to control the spatial arrangement of nanostructures, and the use of continuous-wave illumination, which restricts the operation regime to the steady-state.

In this context, the Marie Skłodowska-Curie Action PATHWAYS seeks to enable a paradigm shift in catalysis by introducing a new class of photocatalysts with tailored properties in space and time, driven by ultrashort light pulses to unlock reaction pathways that offer superior efficiency and selectivity.

The core objective of the project is to introduce new theoretical approaches that can predict how pulsed light excitation of engineered metal nanostructures influences reaction rates, selectivity, and energy use. To achieve this, the project is developing new multi-scale, multiphysics models that describe energy flows through nanostructured catalysts – from light absorption, to hot carrier generation, to energy transfer and reaction activation on the metal surface. These models are intended to guide experiments and set the foundation for data-driven design of photocatalysts, exploring how tailored ultrafast optical pulses can improve reaction outcomes beyond what is possible with traditional continuous-wave illumination. Beyond the immediate scope and duration of the project, the long-term vision of PATHWYAS includes scientific, technological, and societal impact, stemming from the development of new photocatalytic platforms offering sustainable, cost- and energy-effective alternatives to traditional approaches.

Lavoro eseguito dall’inizio del progetto fino alla fine del periodo coperto dalla relazione e principali risultati finora ottenuti

During the reporting period, the project made substantial progress towards its scientific objectives through the activities carried out at the Beneficiary Institution (Politecnico di Milano, Milan, Italy), while building directly on the foundations established during the outgoing phase at the Associated Partner Institution (Rice University, Houston, TX, United States). A central effort of the return phase (Months 13 to 24) focused on turning the models developed in the first part of the Action into a numerical framework capable of describing realistic experimental conditions and of producing predictions directly comparable with measured results.

To this end, the model was extended to include an accurate description of a lab-scale photoreactor, together with the corresponding illumination conditions and heat-exchange processes. This step proved essential to interpret in a robust and quantitative manner the experimental results collected during the outgoing phase on pulsed photocatalysis. In particular, it enabled the understanding of how the temporal distribution of incident light affects photocatalytic efficiency in an intermediate regime, where the timescales of pulsed optical excitation, purely electronic excitation, and photothermal excitation overlap. These advances made it possible to identify pulsed-illumination conditions under which light-induced nonlinearities dominate, leading to an enhancement of the ammonia-decomposition rate as a function of the temporal distribution of photons. As a whole, the main outcome of these activities has been a multiscale modelling framework able to connect microscopic processes at the catalyst surface with macroscopic reactor-scale conditions, providing evidence for the control of the reaction rate with pulsed light.

An additional important line of activity during the return phase concerned the identification of conditions more suitable to investigate ultrafast nonthermal effects in plasmonic photocatalysis, leveraging the new knowledge built throughout the outgoing phase. In this respect, the expertise available at the Beneficiary Institution enabled a comprehensive investigation of hot-carrier dynamics in prototypical plasmonic nanostructures with unique experimental techniques. Combined with the modelling framework developed within the project, these results contributed to identifying a new methodological approach based on sequences of ultrashort pulses, suitable for probing unexplored regimes in which thermal and nonthermal effects display distinct fingerprints and can therefore be disentangled in time. In parallel, the project also addressed spatially structured plasmonic architectures, showing that engineered arrays and metasurface-based platforms are promising systems for investigating and controlling light-driven catalytic processes. The main outcomes of this line of activity were therefore the identification of a new ultrafast methodology for studies on pulsed photocatalysis and the validation of metasurface-based architectures as powerful platforms for future investigations of light-driven chemistry.

Taken together, these achievements significantly strengthened the scientific basis of PATHWAYS, consolidated the methodological framework developed within the Action, and defined clear directions for the continuation of this research beyond the formal end of the project.

Progressi oltre lo stato dell’arte e potenziale impatto previsto (incluso l’impatto socioeconomico e le implicazioni sociali più ampie del progetto fino ad ora)

The research activities conducted during this reporting period of the project focused on a largely unexplored regime for photocatalysis, which typically relies on continuous-wave illumination rather than on temporally structured pulsed excitation. In this sense, the main results obtained within the return phase place the project beyond the current state of the art, both from a methodological point of view and in terms of the photophysical picture emerging for light-driven catalytic processes.

In particular, the main result beyond the state of the art achieved during the return phase of the Action is the identification, through a combined theoretical and experimental approach, of a regime in which light-driven nonlinearities can enhance the rate of photocatalytic events in ways not accessible under conventional continuous-wave illumination. This was supported by a multiscale modelling framework able to describe realistic reactor conditions and bridge them to the microscopic dynamics of nonequilibrium states at the photocatalyst surface. On this basis, the project provided evidence that the temporal distribution of photons is itself a relevant new control parameter for photocatalytic efficiency, and that suitable pulsed-illumination conditions can activate nonlinear responses that remain hidden in more conventional steady-state approaches. These findings significantly expand the current understanding of plasmonic photocatalysis and establish a new methodological route to investigate and optimise light-driven chemistry.

More broadly, the results obtained during the Action as a whole set the stage for a further step beyond the current state of the art, namely the identification of operating conditions in which thermal and nonthermal effects can be selectively enhanced and disentangled, and eventually driven towards a fully nonthermal regime of reaction-rate enhancement at low temperature. In this perspective, the project also showed that spatially engineered plasmonic architectures, such as metasurface-based platforms, provide especially promising systems for this line of investigation, as they offer additional degrees of freedom to control local optical, electromagnetic, thermal and electronic environments. The combination of temporal and spatial engineering of light-matter interactions therefore emerges as a particularly promising direction, contributing to bringing the field of plasmonic-enabled photocatalysis beyond the state of the art.

To ensure further uptake and success of these results, the next steps will require additional research aimed at consolidating the methodology across different materials, nanostructures, and chemical reactions, as well as further benchmarking against conventional steady-state illumination schemes. In parallel, the refinement of the theoretical framework to incorporate more explicitly the microscopic mechanisms identified experimentally will be pivotal to strengthen the predictive power of the approach. In the longer term, beyond the immediate scope of the project and once the scientific framework is further validated, interactions with technological stakeholders may also become relevant for translating these concepts into more applied light-driven catalytic technologies.