Hydrophobic Ni@N-Doped TiO₂ Nanosheet Arrays-Carbon Paper Photocatalyst for CO₂ Photoreduction at Tri-Phase Interfaces

Rational interphase reaction provides a feasible method to overcome the matters of insufficient adsorption of CO₂ molecules at the catalytic sites and competitive hydrogen evolution reaction (HER), which can increase the formation rate and selectivity of carbon derivatives in photocatalytic CO₂ reduction. Herein, a hydrophobic photocatalyst with TiO₂ nanosheet arrays grown on hydrophobic carbon paper (TiO₂-HCP) is fabricated using a combination of magnetron sputtering and hydrothermal method, and its unique structure not only endows it excellent light absorption and effective carrier spatial separation but also avoids the hydrophobic reagent covering reactive sites. When the interphase reaction shifts from solid–liquid diphase to gas-liquid-solid tri-phase, the photocatalytic CO₂ reduction over TiO₂-HCP mainly generates CO molecules and effectively suppresses HER due to the HCP suppressing the mass transfer of H₂O molecules to active sites. Notably, amounts of H₂ byproduct can further react with CO₂/CO to produce high value-added CH₄ resultant by modifying the N-doped TiO₂-HCP with nickel/nickel oxide species. In the tri-phase interfacial CO₂ photoreduction system, the CH₄ formation rate of Ni@N-doped TiO₂-HCP reaches 134.17 µmol m⁻² h⁻¹ (about 74.6% selectivity) and total carbon derivatives selectivity is about 93%.