Crucial roles of triazinic-NO and CO groups in photocatalytic water splitting on graphitic carbon nitride. Issue 9 (3rd February 2021)

• Record Type: Journal Article
• Authors: Ma, Huizhong; Zhang, Xiao; Jin, Fan; Zhou, He; Zhang, Jie; Ma, Yuchen
• Is Part Of: Journal of materials chemistry. Volume 9:Issue 9(2021)
• Page Start: 5522
• Page End: 5532
• Publication Date: 2021-02-03
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d0ta09363g
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Reaction process of photocatalytic water splitting on graphitic carbon nitride. Abstract : As a typical metal-free photocatalyst, water splitting on graphitic carbon nitride (g-C3 N4 ) has drawn increasing attention. Uncovering its reaction mechanism, which still remains a mystery despite extensive studies, would be of great help for the design of efficient metal-free photocatalysts. Through first-principles calculations we discovered that overall water splitting on g-C3 N4 relies heavily on two nonadiabatic transitions and yielding of the vital active site CO. The two nonadiabatic transitions, one between two excited states while another between the excited and the ground states, trigger the reaction and split an H2 O molecule into a triazinic-N–H and triazinic-N–OH pair. Formation of triazinic-N–OH stabilizes electrons in the π* orbitals of g-C3 N4 and thereby facilitates the reduction reaction. CO is developed from triazinic-N–OH. The significance of CO lies in that it provides a site at which another H2 O molecule could split spontaneously into a C–OOH and N–H pair without the aid of photons so that the oxidation evolution reaction could occur thereafter. The local electric field imposed upon the H2 O molecule that is hydrogen-bonded to the triazinic N is a key factor affecting the nonadiabatic transitions and thus splitting of this H2 O. To increase the water splitting efficiency, the stability of CO should be improved as it tends to evolve into triazinic-NO which is inactive for H2 O splitting.