Modulating the Oxidation State of Titanium via Dual Anions Substitution for Efficient N₂ Electroreduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalytic nitrogen reduction reaction (NRR) offers a sustainable route for ammonia synthesis.
• Current NRR catalysts suffer from low ammonia yield and poor selectivity.
• Tuning catalyst properties is crucial for efficient NRR.

Purpose of the Study:

• To develop a novel catalyst for enhanced electrocatalytic nitrogen reduction reaction (NRR).
• To improve ammonia yield, selectivity, and stability in NRR.
• To investigate the effect of dual anion substitution on TiO2 nanohybrid catalysts.

Main Methods:

• Synthesis of N and S dual anions substituted TiO2 nanohybrid catalyst (NS-TiO2/C) using a facile substitution strategy.
• Characterization of the catalyst's structure, composition, and active sites (Ti3+).
• Electrochemical evaluation of NRR performance, including ammonia yield rate, Faradaic efficiency, and long-term stability.

Main Results:

• The NS-TiO2/C catalyst achieved a high NH3 yield rate of 19.97 µg h-1 mg-1cat and a Faradaic efficiency of 25.49%.
• The catalyst demonstrated excellent long-term stability for 50 hours at -0.25 V versus RHE.
• Experimental and theoretical analyses confirmed that N and S dual-substitution regulates Ti oxidation states, induces oxygen vacancies, and enhances N2 chemisorption and activation.

Conclusions:

• The N and S dual-substitution strategy effectively tunes Ti oxidation states and electronic properties of TiO2 nanohybrids.
• The optimized NS-TiO2/C catalyst significantly boosts NRR efficiency by facilitating N2 activation and reducing reaction barriers.
• This work provides a valuable approach for designing advanced electrocatalysts through rational modulation of oxidation states.