Geomimetic, Ultrafast, and One-Step Preparation of an N-Doped Reduced TiO₂ Porous Layer through an Atmospheric Plasma Spraying Approach for Photocatalytic Tetracycline Removal

A geomimetic, ultrafast, and one-step preparation method for an N-doped reduced TiO2 porous layer using the atmospheric plasma spraying (APS) technique is proposed. The secondary gas provided by the APS (H2) is responsible for reducing TiO2, while an acetamide solution stored in the pores of the substrate acted as a nitrogen source for TiO2 doping. Inspired by the nature of volcanic eruptions on Earth, we used a geomimetic vapor-induced pore-forming (VI-PF) mechanism to produce porous N-doped TiO2 via one-step preparation. We varied the acetamide solution concentration to synthesize different samples (TNX, X indicates the wt % of acetamide solution) to approach photocatalytic tetracycline (TC, 20 ppm/100 mL) degradation under AM1.5G solar simulator irradiation. When the acetamide solution concentration was 5 wt %, the sample (TN5) showed the highest lattice-nitrogen content, which gave it the highest photocatalytic degradation efficiency (rate constant = 1.71 × 10–2 min–1) of TC. Moreover, after 15 rounds of recycling tests, the removal rate and crystalline structure remained stable. In addition to experiments, density functional theory (DFT) calculations are also used to verify the experimental results, and they are also consistent with each other. This work is the first study using the APS technique in a single-step process for nitrogen doping and H2 reduction and is a green, cost-effective, time-saving, and promising method for the mass production of porous TiO2.