Enhanced photocatalytic hydrogen generation with Pt Nanoparticles on multi-phase polycrystalline microporous MnO2 photocatalyst

A multi-phase polycrystalline microporous manganese dioxide (MnO2) photocatalyst for light-induced water splitting and hydrogen generation is performed via a redox reaction under various hydrothermal conditions. By tuning the precursor concentrations down to 0.1 M, two kinds of Mn–O functional groups, including pyrolusite structures at 416, 433, 455, 609 and 646 cm−1 and ramsdellite structures at 466 and 576 cm−1, can be obtained by FT-IR. Morphological and phase characterizations are also examined by FE-SEM and XRD techniques, respectively. A series of peaks, corresponding to planes (110) and (200) of our sample can be indexed as a β-MnO2 crystal with a corresponding lattice spacing of 3.11 Å and 2.19 Å. In particular, a significant enhancement of light-induced hydrogen generation by water splitting has been observed at a Pt–MnO2/C photocatalyst with an optimum hydrogen generation rate of 2261 μ mol g−1 h−1 due to the improvement of electro-oxidation of methanol aqueous solutions, compared to a Pt–TiO2/C photocatalyst. The photoelectrochemical measurement also indicates that the multi-phase polycrystalline macroporous MnO2 photocatalyst can indeed effectively inhibit CO poisoning, help CO re-oxidation in the cocatalyst surface and maintain the catalyst's surface area in methanol oxidation and hydrogen generation efficiency.

► The Mn–O functional groups can be obtained by tuning the precursor concentrations.
► Multi-phase polycrystalline microporous MnO2 show superior photocatalytic activity.
► Hydrogen production rate can be promoted in the presence of the MnO2 photocatalyst.
► The use of macroporous MnO2 photocatalyst can effectively inhibit CO poisoning.