RESEARCH ARTICLE

Defect and interface control on graphitic carbon nitrides/upconversion nanocrystals for enhanced solar hydrogen production

¹ Centre for Clean Energy Technology, Faculty of Science, University of Technology Sydney, Broadway, NSW 2007, Australia
² School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264000, China
³ State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
⁴ University of Chinese Academy of Sciences, Beijing 100049, China
⁵ School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
⁶ Institute for Biomedical Materials and Devices (IBMD), Faculty of Science, University of Technology Sydney, Ultimo, NSW 2007, Australia

^* Corresponding authors (emails: Dawei.Su@uts.edu.au (Dawei Su); danwang@ipe.ac.cn (Dan Wang); Guoxiu.Wang@uts.edu.au (Guoxiu Wang))

Received: 22 June 2022
Revised: 10 October 2022
Accepted: 10 October 2022

Abstract

The effective utilization of solar energy for hydrogen production requires an abundant supply of thermodynamically active photo-electrons; however, the photocatalysts are generally impeded by insufficient light absorption and fast photocarrier recombination. Here, we report a multiple-regulated strategy to capture photons and boost photocarrier dynamics by developing a broadband photocatalyst composed of defect engineered g-C₃N₄ (DCN) and upconversion NaYF₄:Yb³⁺,Tm³⁺ (NYF) nanocrystals. Through a precise defect engineering, the S dopants and C vacancies jointly render DCN with defect states to effectively extend the visible light absorption to 590 nm and boost photocarrier separation via a moderate electron-trapping ability, thus facilitating the subsequent re-absorption and utilization of upconverted photons/electrons. Importantly, we found a promoted interfacial charge polarization between DCN and NYF has also been achieved mainly due to Y-N interaction, which further favors the upconverted excited energy transfer from NYF onto DCN as verified both theoretically and experimentally. With a 3D architecture, the NYF@DCN catalyst exhibits a superior solar H₂ evolution rate among the reported upconversion-based system, which is 19.3 and 1.5 fold higher than bulk material and DCN, respectively. This work provides an innovative strategy to boost solar utilization by using defect engineering and building up interaction between hetero-materials.