One-pot in-situ hydrothermal synthesis of ternary In2S3/Nb2O5/Nb2C Schottky/S-scheme integrated heterojunction for efficient photocatalytic hydrogen production

A Nb2C MXene-derived ternary photocatalyst composite (In2S3/Nb2O5/Nb2C) was successfully synthesized through a one-pot in-situ hydrothermal method. The optimized composite shows excellent photocatalytic activity for H2 evolution due to the synergic effect of In2S3/Nb2O5 heterojunction over Nb2C MXene substrate. According to the spectroscopy and electrochemical analysis, the composite has a dramatically narrowed bandgap, which helps to absorb a larger wavelength of light and accelerates the separation of photoexcited charge carriers. Furthermore, a predominate S-scheme heterojunction charge transfer along with Schottky junction were confirmed between In2S3 and NCC, which contribute to increasing the photocatalytic activity for H2 production. [Display omitted] MXene-derived photocatalysts continue to fascinate the research community in developing photo-driven green and sustainable fuel production. However, the efficiency of MXene-derived photocatalyst is still low due to the wide bandgap and high recombination rate of photo-excited charge carriers. Here, we have synthesized the Nb2C MXene-derived ternary photocatalyst via one-pot in-situ hydrothermal method for photocatalytic hydrogen (H2) evolution. The partial oxidation of Nb2C MXene into Nb2O5 nanorods and coupling with In2S3 nanoparticles via in-situ chemical anchoring were the key factors toward high efficiency and long-term stability during photocatalytic H2 evolution. The optimized ternary photocatalyst composite manifested the highest H2 evolution efficiency at 68.8 µmol g−1 h−1, which was 11 and 7.5 times higher than the Nb2O5/Nb2C (NNC) and pure In2S3 photocatalyst, respectively. Moreover, the photocatalytic stability of the optimized ternary photocatalyst composite was analyzed for five consecutive cycles, and above 87% activity retention was observed even after the fifth cycle without any obvious decline. The separation efficiency of photoexcited charge carriers could be attributed to the synergic effect of the In2S3/Nb2O5 heterojunction and the redox reactions at different sites of the composite. More importantly, the participation of Schottky junction and S-scheme heterojunction charge transfer for the obtained novel ternary photocatalyst was evaluated via ultraviolet photoelectron spectroscopy (UPS) and electron paramagnetic resonance (EPR). This research will provide additional insight into the extended potential of MXene-derived ternary photocatalysts towards efficient H2 production to meet