TiO₂/SnO₂/g-C₃N₄ Type-II heterojunction: DFT design, PEC coupling technologies, and degradation mechanisms with...

Area of Science:

• Environmental Science and Engineering
• Materials Science
• Catalysis

Background:

• Photoelectrocatalysis (PEC) offers efficient organic pollutant removal in water.
• Optimizing PEC efficiency through coupling technologies is a significant challenge.
• Developing effective strategies for water remediation is crucial for environmental protection.

Purpose of the Study:

• To propose a novel "Theory-Structure-Performance-Mechanism" experimental framework.
• To design and synthesize a TiO2/SnO2/g-C3N4 composite material.
• To investigate the performance enhancement of PEC by coupling with persulfate (PMS) and Self-Fenton technologies.

Main Methods:

• Density Functional Theory (DFT) calculations for material design.
• Synthesis of TiO2/SnO2/g-C3N4 composite using a time-saving method.
• Experimental evaluation of PEC, PEC-PMS, and PEC-Self-Fenton for rhodamine B (RhB) degradation.
• Identification of heterojunction characteristics and reactive species.
• Analysis of degradation pathways and active sites using condensed Fukui function.

Main Results:

• The synthesized TiO2/SnO2/g-C3N4 exhibited type-II heterojunction characteristics.
• PEC-PMS and PEC-Self-Fenton significantly enhanced RhB removal (94% and 85%) compared to PEC (36%).
• Improved electron utilization was identified as the primary reason for enhanced degradation.
• Specific mechanisms involving •SO4⁻ and •OH radicals were elucidated.
• Condensed Fukui function analysis identified C-N single bonds as preferential attack sites for •OH.

Conclusions:

• The proposed experimental framework effectively guides the design of coupled PEC technologies.
• TiO2/SnO2/g-C3N4 coupled with PMS or Self-Fenton shows superior performance for RhB degradation.
• The study provides insights into reactive species mechanisms and active site identification in PEC systems.