Templated 2D polymer heterojunctions for improved photocatalytic hydrogen production Catherine Aitchison 1 , Soranyel Gonzalez-Carrero 2 , Shilin Yao, Max Benkert 1 , Benjamin Willner 1 , Floriana Moruzzi 1 , James Durrant 2 and Iain McCulloch 1 1 University of Oxford, UK, 2 Imperial College London, UK 2D polymers have emerged as one of the most promising classes of organic photocatalysts for solar fuels production due to their tunability, charge transport properties and robustness. They are however difficult to process and so there have been limited studies into the formation of heterojunction materials incorporating these components. Here we present a novel templating approach to combine an imine-based donor polymer and an acceptor polymer formed through Knoevenagel condensation. Heterojunction formation is shown to be highly dependent on the topological match of the donor and acceptor polymers with the most active templated material found to be between 3 and 9 times more active for photocatalysis than it’s constituent components. Ultrafast transient absorption spectroscopy (TAS) reveals that this improvement is due to faster charge separation and more efficient charge extraction in the templated heterojunction. The templated material shows a very high hydrogen evolution rate of more than 20 mmol h -1 m -2 with an ascorbic acid hole scavenger but also produces hydrogen in the presence of only water and a cobalt based redox mediator.μS-TAS showed the formation of long-lived charge separated species on the templated material even in the absence of ascorbic acid. The ability to form polarons without reductive quenching by a hole scavenger indicates that these materials are ideally suited for incorporation into a Z-scheme. As such photocatalytic testing of the templated materials with reversible redox shuttles will be presented along with combinations of the polymer heterojunctions with various oxygen evolution photocatalysts for overall water splitting. The templating method presented here allows for the formation of a charge separation interface from topologically matched donor and acceptor materials that are otherwise unprocessable; it thus represents a new route to heterojunction formation that could be applicable to many of the vast library of existing 2D polymers, as well as novel structures, in both photocatalysis and wider optoelectronic applications.
E24
© The Author(s), 2021
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