Molecular engineering of polymeric carbon nitride based Donor-Acceptor conjugated copolymers for enhanced photocatalytic full water splitting

Asif Hayat; Naghma Shaishta; Sunil Kumar Baburao Mane; Ashiq Hayat; Javid Khan; Ata Ur Rehman; Tiehu Li

doi:10.1016/j.jcis.2019.10.088

Molecular engineering of polymeric carbon nitride based Donor-Acceptor conjugated copolymers for enhanced photocatalytic full water splitting

J Colloid Interface Sci. 2020 Feb 15:560:743-754. doi: 10.1016/j.jcis.2019.10.088. Epub 2019 Oct 24.

Authors

Asif Hayat¹, Naghma Shaishta², Sunil Kumar Baburao Mane³, Ashiq Hayat⁴, Javid Khan⁵, Ata Ur Rehman⁶, Tiehu Li⁷

Affiliations

¹ College of Chemistry, Fuzhou University, Fuzhou 350100, PR China.
² Department of Post-Graduate Studies and Research in Chemistry, Gulbarga University, Gulbarga 585106, India.
³ School of Chemistry and Chemical Engineering, Guangzhou University, Guangzhou 510006, PR China. Electronic address: sunilkumar.bmane@gmail.com.
⁴ Department of Physics, Quaid Azam University Islamabad, Pakistan.
⁵ School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, PR China. Electronic address: khanj3@mail.sysu.edu.cn.
⁶ School of Chemical Engineering, Northwest University, Xi'an, PR China.
⁷ School of Material Science and Engineering, Northwestern Polytechnical University Xian, Shaanxi, PR China.

PMID: 31706649
DOI: 10.1016/j.jcis.2019.10.088

Abstract

Research based on the full water splitting via heterogenous semiconducting photocatalyst is a significant characteristic nevertheless challenging for determining the energy and environmental crises. With respect to this, a photocatalytic water splitting by visible light through heterojunction semiconductors has been anticipated as a route to the sustainable energy. For the first time, we integrate a potential conjugated donor-acceptor (DA) co-monomer such as 2, 3-dichloroquinoxaline (DCQ) within the structure of polymeric carbon nitride (PCN) by a facile one-pot co-polymerization process. The DCQ which is acting as an organic motif that simulates a nucleophilic attack on the hosting PCN semiconductor which extends into a long chain of the polymer having enormous surface area and remarkable photocatalytic activity for H₂ and O₂ evolution as compared to the parental CNU. The supremacy of molecular geometry with DA ratio is effectively studied by absorbent, calculated band gap and migration of electrons on the photocatalytic performance of as-synthesized CNU-DCQx co-polymer. The density functional theory (DFT) calculation deliver supplementary evidence for the positive incorporation of DCQ in to the PCN matrix with reduced band gap upon copolymerization. Further, the hydrogen evolution rate (HER) for pure CNU with 14.2 μmol/h while for CNU-DCQ_18.0 it is estimated at 124.9 μmol/h which remarkably fueled almost eight times more than blank sample. Similarly, the oxygen evolution rate (OER) analysis indicates the production 0.2 μmol/h (visible) and 1.5 μmol/h (non-visible) for CNU. However, the OER of copolymerized CNU-DCQ_18.0 is found to be 1.9 μmol/h (visible) and 12.8 μmol/h (non-visible) which almost nine times higher than parental CNU. Hence, the output of this work reflects as an important step on the way to tailor-designed and elucidate the promising role of D-π-A system for the rational motifs of productive photocatalysts for forthcoming request.

Keywords: 2,3-dichloroquinoxaline (DCQ); Photocatalysis; Polymeric carbon nitride (PCN); Water oxidation; Water reduction.