Radio Frequency Atmospheric Pressure Plasma Hydrogenated TiO2-x/Ni Foam as an Efficient Photocatalyst

Black titanium dioxide, TiO2-x, was obtained by hydrogenating commercial TiO2 on nickel foam with radio frequency (RF) atmospheric pressure (AP) He/H-2 plasma in short-time (5, 15 and 30 min) at power of 180 W. Voltage and current waveform was used to characterize the RF discharge. Optical emission spectrum (OES) was employed to investigate the active species during the discharge. The field emission scanning electron microscope (FE-SEM) was employed to investigate the influence of the morphology change by plasma. TiO2 nanoparticles of the hydrogenated samples protrude from the surface and are more clearly to be distinguished. The crystallization was characterized by X-ray diffraction (XRD). The X-ray photoelectron spectroscopy (XPS) results showed that TiO2 turned into TiO2-x with the Ti3+ species introduced by the plasma hydrogenation process. The hydrogenated samples presented significant visible light absorbance and narrow band gap, and displayed higher photocatalytic activity than the pristine samples in degrading methylene blue (MB) under xenon lamp irradiation.