Enhancement of photocatalytic activity for overall water splitting by inhibiting reverse reactions and photocorrosion of C3N4 via modified with TiO2 thin layer

Abstract

Rapid H2 and O2 recombination on typical semiconductor photocatalysts and severe photocorrosion side reactions are two critical factors limiting the scale-up application of photocatalytic overall water splitting (OWS) in solar hydrogen generation with high efficiency and stability. In this work, we have developed a new strategy to enhance easy-corroded C3N4 stability by coating a thin TiO2 inert layer and have promoted the stability of the C3N4 catalyst significantly. In addition, this thin layer of TiO2 could suppress the H2 and O2 recombination effectively. TiO2@Pt/C3N4 catalyst showed 130% enhanced activity than that of the naked Pt/C3N4 in pure water (7.63 μmol g−1h−1) and satisfied stability without remarkable decay in the long-term test. The characterization results indicated the corrosion-led NO3− formation rate decreased about three times (1.06 ppm). Besides, a thin TiO2 layer-coated catalyst showed higher photocurrent, longer charge lifetime (6.60 ns), and less charge transfer resistance (27.48 kΩ). The calculation investigation results co-related with the characterization results well. A possible mechanism was proposed to promote photocatalytic OWS by blocking the reverse reaction and suppressing photocorrosion. This study provides new guidance for the design of stable and efficient C3N4-based catalysts for H2 generation via photocatalytic OWS.