Non-photochromic solar energy storage in carbon nitride surpassing blue radicals for hydrogen production

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 10; no. 14; pp. 7728 - 7738
• Main Authors: Wu, Pei-Shan, Lin, Tzu-Jen, Hou, Sheng-Shu, Chen, Chih-Chia, Tsai, Dai-Ling, Huang, Kuan-Hsiang, Wu, Jih-Jen
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 05.04.2022
• Subjects: Carbon; Carbon nitride; Crystal structure; Crystallinity; Density functional theory; Energy conversion; Energy storage; Hydrogen evolution; Hydrogen production; Molecular structure; Photocatalysis; Photochromism; Photoelectrons; Photon absorption; Potassium; Radicals; Solar energy; Solar energy conversion; Storage capacity
• DOI: 10.1039/D1TA10091B
• ISSN: 2050-7488

Potassium poly(heptazine imide) (KPHI) exhibiting the dual functionality of photon absorption and photoelectron storage for solar energy conversion is a new class of ionic two-dimensional (2D) carbon nitrides. Rather than forming blue radicals upon storing photoelectrons in the yellow crystalline KPHIs, here non-photochromic solar energy storage in the in-plane short-range-ordered KPHI is reported, which demonstrates superior photocatalytic and dark photocatalytic activities for hydrogen evolution. Density functional theory calculations confirm that the electron storage capacity of the short-range-ordered KPHI is higher than that of the crystalline one. Moreover, the molecular structure remains unchanged after electrons are stored, resulting in non-photochromic solar energy storage in short-range-ordered KPHI. In crystalline KPHI, the stored photoelectrons drive the change of potassium ion locations to form a blue radical. This work demonstrates that the photophysical properties of light-storing carbon nitrides are tunable by modifying the microstructure of KPHIs towards efficient solar energy storage and conversion.