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Phase-selective active sites on ordered/disordered titanium dioxide enable exceptional photocatalytic ammonia
Jinsun Lee1,2, Xinghui Liu1,2, Ashwani Kumar1,2
1Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS) 2066 Seoburo, Jangan-gu Suwon 16419 Republic of Korea hyoyoung@skku.edu.
Chemical Science
|August 5, 2021
Summary
Engineered titanium dioxide (TiO2) with selective defects enhances photocatalytic nitrogen (N2) fixation to ammonia (NH3). This breakthrough overcomes previous limitations in selectivity and yield for sustainable ammonia production.
Area of Science:
- Materials Science
- Catalysis
- Photochemistry
Background:
- Photocatalytic nitrogen (N2) fixation to ammonia (NH3) using defect-engineered titanium dioxide (TiO2) is promising but hindered by poor selectivity and low yields.
- Understanding N2 adsorption on phase-selective defect sites and band alignment is crucial for optimizing TiO2 photocatalysts.
Purpose of the Study:
- To theoretically investigate N2 adsorption on disordered anatase (Ad) and rutile (Rd) TiO2 phases.
- To synthesize a phase-selective disordered-anatase/ordered-rutile TiO2 photocatalyst (Na-Ad/Ro) for enhanced N2 fixation.
- To elucidate the synergistic effects enabling efficient photocatalytic ammonia synthesis.
Main Methods:
- Theoretical calculations to predict N2 adsorption and reaction barriers on different TiO2 phases.
- Synthesis of Na-Ad/Ro TiO2 via sodium-amine treatment of P25-TiO2 under ambient conditions.
- Characterization of photocatalytic activity for NH3 formation under solar illumination.
Main Results:
- Theoretical predictions showed preferential N2 adsorption and lower energy barriers on disordered anatase (Ad) defect sites.
- The synthesized Na-Ad/Ro photocatalyst achieved an NH3 formation rate of 432 μmol g−1 h−1, significantly outperforming other defect-rich TiO2 materials.
- A high apparent quantum efficiency of 13.6% at 340 nm was recorded, demonstrating efficient solar energy utilization.
Conclusions:
- Defect sites on disordered anatase TiO2 exhibit superior N2 adsorption capabilities, guiding catalyst design.
- The Na-Ad/Ro photocatalyst demonstrates highly efficient and selective N2 fixation to NH3.
- Synergistic effects, including selective chemisorption, enhanced light absorption, suitable band alignment, and rapid charge separation, are key to the improved performance.
