Water Oxidation with Cobalt-Loaded Linear Conjugated Polymer Photocatalysts.

Reiner Sebastian Sprick,Alexander J Cowan,Catherine M Aitchison,Andrew I Cooper,Yuanxing Fang,Yang Bai,Xinchen Wang,Martijn A Zwijnenburg,Zheng Chen

doi:10.1002/anie.202008000

Abstract

The first examples of linear conjugated organic polymer photocatalysts that produce oxygen from water after loading with cobalt and in the presence of an electron scavenger are reported. The oxygen evolution rates, which are higher than for related organic materials, can be rationalized by a combination of the thermodynamic driving force for water oxidation, the light absorption of the polymer, and the aqueous dispersibility of the relatively hydrophilic polymer particles. We also used transient absorption spectroscopy to study the best performing system and we found that fast oxidative quenching of the exciton occurs (picoseconds) in the presence of an electron scavenger, minimizing recombination.

Highlights

We have demonstrated the first use of cobalt-loaded conjugated linear organic polymers as photocatalysts for water oxidation
P10, a dibenzo[b,d]thiophene sulfone homopolymer, was the best-performing material after photo-deposition of a cobalt co-catalyst, giving oxygen evolution rates that significantly exceed those observed for related triazine-based frameworks under identical experimental conditions
The relative oxygen evolution activity of the polymers can be understood in terms of their predicted ionization potentials, which control the driving force for water oxidation, along with the optical gap and the aqueous dispersibility of the polymers

Summary

Introduction

Photocatalysts for sacrificial half reactions that produce either hydrogen or oxygen in the presence of hole or electron scavengers.[1,3] This has resulted in systems that perform overall water splitting with promising solar-to-hydrogen efficiencies.[4,5,6,7]. A small number of covalent triazine-based frameworks,[27,28,29,30] covalent organic frameworks,[31] and CMPs[32,33] have been reported to facilitate water oxidation after loading with metal co-catalysts, while poly(benzimidazobenzophenanthroline) is a rare example of a photoanode for water oxidation.[34] There are strong drivers to diversify this small range of organic photocatalysts for water oxidation and, to develop materials that function under sunlight; that is, materials that absorb visible rather than only UV light This could allow us to construct allorganic Z-schemes that comprise an organic proton reduction catalyst coupled with an organic water oxidation catalyst

Results and Discussion

Conclusion

Conflict of interest