Periodic Reporting for period 1 - PolyNanoCat (Polymer Nanoparticle for Hydrogen Evolution)
Reporting period: 2021-01-01 to 2022-12-31
Global energy supply, and its impact on the environment, is one of the biggest technological challenges to be addressed. The synthesis of fuels and chemicals from sunlight, water and carbon dioxide is an important route to sustainable development beyond fossil fuels. Organic semiconductors materials have emerged as potentially low-cost photocatalysts for hydrogen evolution with promising efficiencies, including carbon nitrides, conjugated polymers, and covalent organic frameworks. However, the photophysics of such organic semiconductors photocatalysts and how these determined photocatalytic performances remain limited. Discovering the correlation between the photocatalytic activity and the photophysical properties of polymer photocatalysts will guide the design of novel, stable and efficient catalysts for solar-to-fuel conversion.
In PolyNanoCat project, we focused on state-of-the-art polymers donor:acceptor heterojunction nanoparticles for hydrogen evolution, addressing their previously unexplored photophysical properties which determine their function. Advanced transient optical emission and absorption spectroscopies were used to investigate how the structure of the polymer heterojunction nanoparticles affects the photocatalysis mechanism.
We reported highly efficient polymer donor/acceptor heterojunction nanoparticles with hydrogen evolution rate (HER) up to 73.7 mmol h−1 g−1 under simulated solar irradiation, and quantum efficiencies of ~ 9 % across the visible spectrum, among the most efficient organic hydrogen evolution photocatalysts reported. The photophysical studies of such nanoparticles revealed that organic semiconductor nanoparticles photocatalysts containing a donor/acceptor heterojunction structure can intrinsically generate remarkably long-lived and reactive charges in the timescales need it for photocatalysis (milliseconds) even in the absence of added metal cocatalyst or sacrificial electron donors. This demonstrates that in heterojunction nanoparticles the mechanism does not rely on a rapid reductive exciton quenching by a sacrificial reagent to drive charge separation as observed in single polymers. Our studies also revealed that the nanomorphology of the donor/acceptors domains in the nanoparticle strongly influences the charge recombination and therefore their activity. These photophysical studies most likely represent the state-of-the-art for organic semiconductors heterojunction photocatalysts leading to guidelines for designing more efficient organic nanoparticles.
In PolyNanoCat project, we focused on state-of-the-art polymers donor:acceptor heterojunction nanoparticles for hydrogen evolution, addressing their previously unexplored photophysical properties which determine their function. Advanced transient optical emission and absorption spectroscopies were used to investigate how the structure of the polymer heterojunction nanoparticles affects the photocatalysis mechanism.
We reported highly efficient polymer donor/acceptor heterojunction nanoparticles with hydrogen evolution rate (HER) up to 73.7 mmol h−1 g−1 under simulated solar irradiation, and quantum efficiencies of ~ 9 % across the visible spectrum, among the most efficient organic hydrogen evolution photocatalysts reported. The photophysical studies of such nanoparticles revealed that organic semiconductor nanoparticles photocatalysts containing a donor/acceptor heterojunction structure can intrinsically generate remarkably long-lived and reactive charges in the timescales need it for photocatalysis (milliseconds) even in the absence of added metal cocatalyst or sacrificial electron donors. This demonstrates that in heterojunction nanoparticles the mechanism does not rely on a rapid reductive exciton quenching by a sacrificial reagent to drive charge separation as observed in single polymers. Our studies also revealed that the nanomorphology of the donor/acceptors domains in the nanoparticle strongly influences the charge recombination and therefore their activity. These photophysical studies most likely represent the state-of-the-art for organic semiconductors heterojunction photocatalysts leading to guidelines for designing more efficient organic nanoparticles.
PolyNanoCat project aimed to investigate the correlation between the photophysical properties and the photocatalytic activity of polymer heterojunction nanoparticles photocatalysts required for a better understanding of the solar-to-fuel mechanism and further provide guidance for the design of efficient photocatalysts. The project was developed in three phases; first donor:acceptor heterojunction nanoparticles were optimized, and their photocatalytic activity and stability for hydrogen evolution under simulated solar irradiation were screened, partnered with our collaborator from the University of Oxford, UK. In parallel, the experimental design and in-depth characterization of the photophysical properties of the best-performing nanoparticles were conducted by using advanced transient absorption and emission spectroscopies on timescales ranging from picoseconds to seconds. Finally, we rationalized the information gained from both photocatalytic and photophysical studies to establish structure-activity relationships for polymer/fullerene and no-fullerene acceptor heterojunction nanoparticles.
The photophysical studies revealed the efficient exciton dissociation at the donor:acceptor heterojunctions within the nanoparticles in picosecond timescale, leading to the accumulation of remarkably long-lived photogenerated charges in millisecond to second timescale, even in the absence of added co-catalyst or sacrificial electron donor. These charges were efficiently extracted upon the addition of the Pt co-catalyst and ascorbic acid as sacrificial electron donor, which suggests that they were responsible for the photocatalytic activity of the nanoparticles.
The project outcomes were disseminated through publications in high-impact peer-reviewed journals, and presentations in national (UK) and international conferences (in EU) by Dr. Gonzalez-Carrero, including invited talks, oral presentations, and poster contributions. In addition, the project was disseminated to non-scientific audiences.
The photophysical studies revealed the efficient exciton dissociation at the donor:acceptor heterojunctions within the nanoparticles in picosecond timescale, leading to the accumulation of remarkably long-lived photogenerated charges in millisecond to second timescale, even in the absence of added co-catalyst or sacrificial electron donor. These charges were efficiently extracted upon the addition of the Pt co-catalyst and ascorbic acid as sacrificial electron donor, which suggests that they were responsible for the photocatalytic activity of the nanoparticles.
The project outcomes were disseminated through publications in high-impact peer-reviewed journals, and presentations in national (UK) and international conferences (in EU) by Dr. Gonzalez-Carrero, including invited talks, oral presentations, and poster contributions. In addition, the project was disseminated to non-scientific audiences.
Developing efficient and cost-competitive light-harvesting technologies requires the continuous development of new and existing materials. Organic semiconductors nanoparticles that contain a donor/acceptor heterojunction structure are currently among the most efficient visible light-active hydrogen evolution photocatalysts. It is expected that the photophysical studies carried out in PolyNanoCat project serve as a tool for the rational design of new and more efficient organic semiconductors towards the 10 % Solar-to-hydrogen (STH) efficiency benchmark; opening a broad library of organic semiconductors to explore as photocatalysts for solar fuel production. In addition, opened potential applications of such heterojunction nanoparticles in water-splitting Z-schemes and in driving technologically desirable oxidations, two exciting research lines to explore.