Photocatalytic reduction of CO2 into fuels offers a promising avenue to tackle present energy challenges and mitigate global warming. At present, TiO2 has been widely used in photocatalytic CO2 reduction reactions, and element doping can optimize the band structure of TiO2 to improve the efficiency of photocatalytic CO2 reduction. In this work, TiO2 doped with different content of N was prepared using TiN as the precursor through a simple one-step calcination method. Under optimized conditions, the optimal CO yield of the modified photocatalyst is 41.1 μmol g− 1 h− 1, which is 8 times higher than that of p25 type TiO2. Density functional theory (DFT) calculations confirmed that N-doping can reduce the band gap of TiO2 and decrease the Gibbs free energy of CO2 reduction reaction. In-situ-XPS indicated that N-doping can enhance the activation of CO2 by enriching photo generated electrons. Additionally, In-situ-FTIR spectra were employed to detect intermediates and track variations in the consumption of H2O and CO2, providing deeper insights into the mechanism responsible for enhancing efficiency. Our work addresses the deficiencies of the past and provides more detailed theoretical insights for the accelerated photocatalytic reduction of CO2 by N-doping TiO2.

Carbon nanotube fiber is a promising material in electrical and electronic applications, such as, wires, cables, batteries, and supercapacitors. But the problem of joining carbon nanotube fiber is a main obstacle for its practical development. Since the traditional joining methods are unsuitable because of low efficiency or damage to the fiber structure, new methods are urgently required. In this study, the joining between carbon nanotube fiber was realized by deposited nickel–copper doublelayer metal via a meniscus-confined localized electrochemical deposition process. The microstructures of the double-layer metal joints under different deposition voltages were observed and studied. It turned out that a complete and defect-free joint could be fabricated under a suitable voltage of 5.25 V. The images of the joint cross section and interface between deposited metal and fiber indicated that the fiber structure remained unaffected by the deposited metal, and the introduction of nickel improved interface bonding of double-layer metal joint with fiber than copper joint. The electrical and mechanical properties of the joined fibers under different deposition voltages were studied. The results show that the introduction of nickel significantly improved the electrical and mechanical properties of the joined fiber. Under a suitable deposition voltage, the resistance of the joined fiber was 37.7% of the original fiber, and the bearing capacity of the joined fiber was no less than the original fiber. Under optimized condition, the fracture mode of the joined fibers was plastic fiber fracture.