Enhanced photocatalytic performance of direct Z-scheme g-C3N4–TiO2 photocatalysts for the decomposition of formaldehyde in air

TLDR

Formaldehyde is a major indoor pollutant that can cause nasal tumors and skin irritation, and photocatalytic oxidation is considered the most promising strategy for its decomposition. The study aims to prepare, for the first time, a direct g‑C3N4–TiO2 Z‑scheme photocatalyst via a simple calcination route using inexpensive P25 and urea, and to offer new insights into designing high‑performance Z‑scheme photocatalysts for indoor air purification. The photocatalyst was synthesized by calcining P25 and urea, and its activity was assessed by measuring the photocatalytic oxidation of formaldehyde in air. The Z‑scheme photocatalyst’s activity strongly depends on g‑C3N4 content, with the optimal U100 sample achieving a 7.36 × 10⁻² min⁻¹ rate constant—2.1 times higher than pure P25—due to efficient charge‑carrier separation.

Abstract

Formaldehyde (HCHO) is a major indoor pollutant and long-term exposure to HCHO may cause health problems such as nasal tumors and skin irritation. Photocatalytic oxidation is considered as the most promising strategy for the decomposition of HCHO. Herein, for the first time, a direct g-C3N4-TiO2 Z-scheme photocatalyst without an electron mediator was prepared by a facile calcination route utilizing affordable P25 and urea as the feedstocks. Photocatalytic activities of the as-prepared samples were evaluated by the photocatalytic oxidation decomposition of HCHO in air. It was shown that the photocatalytic activity of the prepared Z-scheme photocatalysts was highly dependent on the g-C3N4 content. At the optimal g-C3N4 content (sample U100 in this study), the apparent reaction rate constant was 7.36 × 10(-2) min(-1) for HCHO decomposition, which exceeded that of pure P25 (3.53 × 10(-2) min(-1)) by a factor of 2.1. The enhanced photocatalytic activity could be ascribed to the formation of a g-C3N4-TiO2 Z-scheme photocatalyst, which results in the efficient space separation of photo-induced charge carriers. Considering the ease of the preparation method, this work will provide new insights into the design of high-performance Z-scheme photocatalysts for indoor air purification.