Metal-Free Pyrene-Based Conjugated Microporous Polymer Catalyst Bearing N- and S-Sites for Photoelectrochemical Oxygen Evolution Reaction.

Sabuj Kanti Das,Saptarsi Mondal,Asim Bhaumik,Avik Chowdhury,Sanjib Shyamal,Manisha Das,Ramendra Sundar Dey,Debabrata Chakraborty

doi:10.3389/fchem.2021.803860

Abstract

The development of an efficient, sustainable, and inexpensive metal-free catalyst for oxygen evolution reaction (OER) via photoelectrochemical water splitting is very demanding for energy conversion processes such as green fuel generators, fuel cells, and metal-air batteries. Herein, we have developed a metal-free pyrene-based nitrogen and sulfur containing conjugated microporous polymer having a high Brunauer-Emmett-Teller surface area (761 m2 g−1) and a low bandgap of 2.09 eV for oxygen evolution reaction (OER) in alkaline solution. The π-conjugated as-synthesized porous organic material (PBTDZ) has been characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state 13C (cross-polarization magic angle spinning-nuclear magnetic resonance) CP-MAS NMR, N2 adsorption/desorption analysis, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) experiments. The material acts as an efficient catalyst for photoelectrochemical OER with a current density of 80 mA/cm2 at 0.8 V vs. Ag/AgCl and delivered 104 µmol of oxygen in a 2 h run. The presence of low bandgap energy, π-conjugated conducting polymeric skeleton bearing donor heteroatoms (N and S), and higher specific surface area associated with inherent microporosity are responsible for this admirable photoelectrocatalytic activity of PBTDZ catalyst.

Highlights

The massive rise of the global population over recent decades is causing a huge increase in the demand for energy for society (Adam, 2021)
For further confirmation of PBTDZ synthesis, solid-state 13C NMR data has been recorded (Figure 1B) in which the broad peaks which appeared from 120 to 150 ppm suggested the existence of aromatic C atoms of pyrene as well as benzothiadiazole moieties
An efficient and cost-effective metal-free conjugated microporous polymer PBTDZ was synthesized via Suzuki C-C cross-coupling reaction between a tetraboronate ester and 4,7-dibromo-2,1,3-benzothiadiazole

Summary

INTRODUCTION

The massive rise of the global population over recent decades is causing a huge increase in the demand for energy for society (Adam, 2021). The ease of fabrication of organic functional groups at the pore surface and high specific surface area make them desirable materials for various energy harvesting applications Several members of this family of materialssuch as metal-organic framework (MOF) (Ma et al, 2020), metalized/metal free covalent organic framework (COF) (Lin et al, 2018; Hosokawa et al, 2021), and porous organic polymer (POP) (Wang et al, 2020), have already been utilized as efficient OER photo-electrocatalysts. PBTDZ possesses a highly specific surface area with a low bandgap, and it shows excellent activity and recyclability in the photoelectrochemical water oxidation reaction. The isolated yield of the final product namely PBTDZ was calculated and found to be 76%

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT