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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]

Due to its fuel-efficient and environmentally friendly nature, the electrocatalytic nitrogen reduction reaction (NRR) has drawn significant attention. However, most of the catalysts reported for the NRR are noble metals or oxides, which are expensive and poorly conductive. Therefore, the development of effective electrocatalysts for nitrogen (N2) fixation under ambient conditions has become a promising field. Herein, we report fluorine-free Ti3C2Tx (T = O, OH) nanosheets with a small size (∼50–100 nm lateral size) as catalysts for the NRR. The as-prepared materials achieved a high NH3 yield (36.9 μg h−1 mgcat−1) and faradaic efficiency (9.1%) at −0.3 V vs. reversible hydrogen electrode (RHE) in 0.1 M HCl. The size effect and fluorine-free properties make the performance around two times higher than that in the case of a fluorine-based treatment. This paper inspires us to pursue the extreme size (e.g. quantum dots) of MXenes which will enhance its NRR property greatly. [ABSTRACT FROM AUTHOR]