Skip to main content

Integrating photochemistry in nanoconfined carbon-based porous materials in technological processes

Periodic Reporting for period 4 - PHOROSOL (Integrating photochemistry in nanoconfined carbon-based porous materials in technological processes)

Reporting period: 2020-01-01 to 2022-02-28

The ambition of PHOROSOL is to develop more efficient materials to boost technologies for light energy utilization, profiting from the dual nature of nanopore carbons as strong light absorbing materials with unique electronic features and nanoporosity.

Context

The disruptive approach of the project is based on exploiting the potentialities of earth-abundant and metal-free carbons with well-defined nanopores for photochemical applications.

Our pioneering works have shown that it is possible to harvest light in these materials and to promote photoinduced reactions inside the pores.

Owing to their versatility and availability, it is highly feasible to push the nanoporous carbons as additives to semiconductors and as sustainable metal-free photocatalysts for various fields of applications in the fields of gas sensing, energy conversion and environmental protection.

Their electrical conductivity is lower than that of graphene or nanotubes, but is still better than most semiconductors. They also offer the advantage of coupling high adsorption features to tunable photoactivity; the challenge is in further enhancing the photochemical activity by balancing the surface composition, porosity, and charge-carrier mobility.

Conclusions
The main conclusions of PHOROSOL are:
1) Origin of photoactivity of carbons. Our work has demonstrated formation of radical species upon irradiation of nanoporous carbons, showing the possibility of modulating visible light activity via functionalization and nanopore confinement.

2) Solar energy conversion. We have shown the application of photoresponsive carbons in transforming CO2 and H2O into sustainable fuels, a major global research priority. They are also capable of promoting other photocatalytic transformations of interest for the productive sector.

3) Photoassisted synthesis of porous carbons. We have demonstrated that it is possible to use light activation in the synthesis of porous carbons with controlled features.

4) Nanopore confinement at extreme conditions. A tight nanopore confinement of certain probes -oxidizers- in porous carbons has been revealed to be critical to the performance of the resulting material in terms of releasing thermal energy.

5) Photoluminescence of porous carbons. We have been able to measure light emission features in nanoporous carbons, which has a significant impact on the development of selective sensors.
Several research directions were explored:
Understanding Photochemical Activity of Porous Carbons Our research has been focused in understanding the mechanisms governing the carbon photoinduced reactions and the fate of the photoexcited states of the carbon atoms. Data has demonstrated the formation of radical species upon irradiation in the full UV-VIS spectrum, as well as their stabilization through reactions with other species confined in the pores.
Porous carbon catalysts for solar energy conversion. We have explored the application of photoresponsive porous carbons in transforming CO2 and H2O into sustainable fuels. As photoanodes for the photoreforming of H2O, remarkable photocurrents have been recorded for carbons with varied composition. A balance of both aspects is essential to prevent photocorrosion of the anodes upon long-term operation. In the photorreduction of CO2 we have obtained good results towards the conversion into CO+H2 or HCHO depending on the applied conditions.
Porous Carbons Additives in Photocatalytic Paints, for the degradation of indoor/outdoor pollutants. We have shown that the carbon matrix affects the dynamics of the charge transport, creating a percolation path for the majority carriers. Such photocatalytic paints are able to degrade the pollutants, with good long-term stability. A PhD thesis has been the focus on this activity.
Photoassisted Synthesis of Porous Carbons. We have investigated the use of light activation to promote the cross-linking of polymer precursors in the synthesis of porous carbons. By changing the chemistry of the precursor it is possible to control the porosity of the carbons. A PhD thesis has been the focus on this activity.
Implications of Nanopore Confinement at Extreme Conditions. A tight nanopore confinement of certain salts in porous carbons has been revealed to be critical to the performance of releasing thermal energy; such mixtures can compete with the best nanoenergetic materials in the market, with better safety performance. A PhD thesis has been the focus on this activity.
Photoluminescence of Porous Carbons. The photoluminescence of carbon materials has only been demonstrated for carbons with high electron mobility and degree of transparency. In PHOROSOL we have been able to measure light emission features in porous carbons, which has a significant impact on the development of sensors with improved sensitivity and selectivity.
Sensing performance of porous carbons. We have explored resistive gas sensors based on nanoporous carbons for detecting low concentration of toxic industrial gases. Our results have shown important modifications of the resistive character of the materials upon the confinement state of the gases on the nanopores, and modulation of the resistive response through photocarriers

Dissemination activities include publication in high impact peer-reviewed journals, participation in international conferences and events for the general audience, organization of meetings and conferences. These activities have involved all the members of the group. The results obtained have been published in high impact open access journals (Carbon, Advanced Science) and book chapters. A patent has also been filed.
Our investigations have contributed to unravel the role of the nanoporous carbons features in their photochemical performance, and to stimulate research leading to better understanding their exciting behavior. This has long been neglected and considered as having no physical bases.
Based on our outcome, nanoporous carbons are being considered in beyond adsorption applications. We anticipate a bright future in photovoltaics, smart-self-cleaning surfaces, photocorrosion protection, or solar energy conversion and CO2 mitigation.
Part of PHOROSOL team has worked on investigating the origin of the interactions of light within nanopores, and the potential fields of application. An exciting application is transforming CO2 and H2O into sustainable fuels. Carbon catalysts have been shown to be among the most interesting candidates to replace metallic catalysts in the production of CO2-derived solar fuels.
The team has been able to measure light emission features in porous carbons, a very challenging topic in not transparent materials. The team has worked in controlling the emission/absorption features, and the stability in different environments, as these may be the key to broadening the portfolio of applications beyond those initially anticipated in the project (e.g. photonic conversion layers in solar cells).
The tight nanopore confinement of oxidizers in porous carbons has revealed to be critical to the performance of the composite in terms of releasing thermal energy. Although plenty of materials show such ability to release energy, only a few show adequate stability for safe storage and use. These results provide a proof of concept for a novel family of energetic materials based on nanoporous carbons as the main ingredient.
PHOROSOL Overview