Superhydrophobic Photochromic TiO₂/Bi₂WO₆ Materials Promote Photocatalytic CO₂ Reduction under Visible Light Irradiation

Photocatalytic CO2 reduction to renewable fuels presents a promising strategy to mitigate greenhouse effects, yet challenges persist in achieving high efficiency due to CO2's thermodynamic stability and competitive H2O adsorption. Herein, we develop a superhydrophobic photochromic TiO2/Bi2Wo6 (TBW-2O) nanocomposite that synergistically enhances visible-light-driven CO2 reduction. Dynamic charge management via reversible W6+↔W5+ transitions not only suppresses charge recombination but also facilitates electron transfer for CO2 activation, as evidenced by in situ XPS and EPR. The superhydrophobic surface designed with sodium oleate (water contact angle >150°) selectively enriches CO2 at the active sites compared to H2O (ΔGCO2 = -2.88 eV vs ΔGH2O = -1.17 eV). Dual heterojunction effects (Type II + Z-scheme) between TiO2 and Bi2WO6 optimize light absorption and redox potentials. The optimized TBW-2O achieves exceptional CH4 and CO production rates of 48.09 and 37.40 μmol·g-1·h-1, respectively, representing 19.7- and 6.6-fold enhancements over pure TiO2. Notably, it attains an apparent quantum yield (AQY) of 0.35% (CH4) and 0.32% (CO) at 350 nm without sacrificial agents or noble metals. Combined experimental and theoretical analyses reveal that the W6+/W5+ redox cycle and hydrophobic interface collaboratively promote COOH/CHO intermediate formation, steering the reaction pathway toward CH4. This work provides a design blueprint for multifunctional photocatalysts integrating photochromism and surface wettability control.