Harnessing mesoporosity and nitrogen doping to engineer a superior carbon-TiO2 photocatalyst for methylene blue degradation

Abstract

Addressing the global water crisis requires advanced solutions for persistent pollutants like methylene blue (MB), where traditional TiO₂ photocatalysis is limited by wide bandgap and charge recombination. This study develops a nitrogen-doped carbon-modified TiO₂ (mNC-TiO₂) photocatalyst to overcome these challenges, combining nitrogen doping (2.5%) with a conductive carbon matrix to enhance visible-light absorption, charge separation, and wastewater treatment efficacy. The material was synthesized via a microemulsion-liquid crystal template method, forming a mesoporous nanostructure (298 m² g⁻¹ surface area, 5.4 nm pores) with oxygen vacancies and reduced bandgap (2.85 eV). Characterization (XRD, XPS, FE-SEM, EDX, and HR-TEM) verified its optimized structure, while photocatalytic tests achieved 94.7% MB degradation under UV—3.1× more efficient than dark adsorption (30.1%). The reaction followed pseudo-first-order kinetics (k₁ = 4.8 × 10⁻² min⁻¹), with ˙OH and ˙O₂⁻ as dominant oxidants. Remarkably, mNC-TiO₂ retained > 85% efficiency over five cycles due to its stable mesostructure and HNO₃-regenerable sites. The carbon matrix served dual roles as electron acceptor and molecular adsorbent, synergizing with nitrogen-induced bandgap narrowing for sustained performance. These results demonstrate a rationally designed photocatalyst with practical potential for organic pollutant removal.