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Transition metal (M = Cu, Fe and Ni) modified TiO2 nanosheets were synthesized via a microwave assisted hydrothermal method. The as-fabricated catalysts were characterized using X-ray diffraction (XRD), electron microscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption, UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence emission (PL), transient photocurrent–time curves and electrochemical impedance spectroscopy (EIS). The results indicated that the loading of transition metals did not influence the crystal structure and morphology of anatase TiO2, while the specific surface area, the absorption in the visible region and the charge transfer were enhanced. In addition, photocatalytic nitrogen fixation over the transition metal modified TiO2 nanosheets was also evaluated. Under the irradiation of simulated sunlight, transition metal modified TiO2 exhibited better photocatalytic performance and stability than pristine TiO2. Among these samples, Cu/TiO2 with the optimal mass content of 1.0% achieved the best NH4+ generation performance and the evolution rate reached 6.78 mmol g−1 h−1 with the relative standard deviation of 2.33%. Furthermore, a plausible mechanism coupled with interfacial charge transfer (IFCT) over Cu modified TiO2 nanosheets was proposed in our present study. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles co-modified with CuOx (0≤x≤2) and carbonaceous materials were prepared with a simple hydrolysis and photo-reduction method for photocatalytic hydrogen generation. SEM/TEM and XPS analysis indicated that the carbonaceous materials were mostly coated on the TiO2 surface and clearly revealed that the Cu species exhibited multivalence states, existing as CuOx (0≤x≤2). The optimal catalyst showed a 56-fold enhanced hydrogen evolution rate compared with that of the pure C/TiO2 catalyst. Further, an intensive multiple electron transfer effect originating from CuOx and the carbonaceous materials is proposed to be responsible for the elevated photoactivity. CuOx species serve as electron donors facilitating charge carrier transfer and proton reduction sites. The carbonaceous materials function as the “bridge” that transfers the electrons of TiO2 to the CuOx species, which provides a new route for electron transfer and reinforces the effect of CuOx as a co-catalyst. In this study, the CuOx and C co-modified TiO2 catalyst was prepared with multiple electron transport pathways and enhanced hydrogen production evolution, which provides a deep understanding for the design of co-catalyst-based photocatalysts. [ABSTRACT FROM AUTHOR]