Sicong Wang: Polymer Dots for Solar Chemicals: Material Design and Photocatalytic Mechanism

Abstract

The urgent need to replace traditional fossil fuels has accelerated the development of sustainable energy technologies, with photocatalysis emerging as one promising approach. Conjugated polymer dots (Pdots) have gained increasing attention recently for various photocatalytic applications such as hydrogen production and CO2 reduction. However, the use of Pdots as photocatalysts for the production of value-added chemicals, such as hydrogen peroxide (H2O2), aldehydes, and organic acids, remains largely unexplored in this field. My research aims to fill the knowledge gap in such applications and thoroughly investigate key factors that govern photocatalytic activity, including charge transfer efficiency, Pdots morphology, surface reaction kinetics, and the spatial distribution of catalysts within Pdots.

The research in this thesis begins with the development and study of an efficient Pdots photocatalyst composed of PFBT as electron donor and PCBM as electron acceptor for H2O2 production coupled with methanol (MeOH) oxidation into formate (paper I) with a high quantum efficiency of up to 14 %. By optimizing the polymer structure, truxene-based polymers (paper II) can produce a comparable H2O2 and formate production efficiency to the PFBT/PCBM system without the use of a PCBM electron acceptor. In order to further expand the applicable condition to neutral pH region, in Paper III, a molecular catalyst for alcohol oxidation, TEMPO, is covalently grafted onto PFBT backbone. Relative Pdots realize H2O2 production and MeOH oxidation under neutral conditions for the first time. From the study, the photocatalytic activity is found to be low, probably restricted by insufficient interactions between the TEMPO catalysts within the Pdots and MeOH molecules in the solution. Paper IV therefore successfully develops a new method to distribute the TEMPO catalyst close to the surface of Pdots while keeping their good interactions with PFBT. At the same time, an electrostatic adsorption method is used to fabricate Pdots films while preserving high catalytic activity.