Zhenjie Tang

G-C₃N₄ has emerged as a promising metal-free semiconductor for optoelectronic applications due to its suitable bandgap, excellent stability, and low cost. However, enhancing its photoresponse efficiency in practical devices remains a challenge. In this work, a high-performance self-powered photodetector was developed using a g-C₃N₄/textured Si n-n heterojunction fabricated via a simple solution process. The device exhibits excellent diode characteristics with a rectification ratio of ~4.9 × 10² and an ideality factor of 1.41. It achieves broadband detection from 405 to 980 nm, a high responsivity of 3.2 A/W, a specific detectivity of 1.9 × 10¹⁴ Jones, and fast response speeds of 44/36 ms at 650 nm under zero bias. Significantly, the textured Si-based device shows approximately tenfold higher performance than its planar Si counterpart, owing to enhanced light absorption from the textured surface. The combination of excellent photoresponse and simple fabrication makes the g-C₃N₄/textured Si n-n heterojunction a promising candidate for low-cost, high-performance optoelectronic applications.

Utilizing hydrogen as a viable substitute for fossil fuels requires the exploration of hydrogen storage materials with high capacity, high quality, and effective reversibility at room temperature. In this study, the stability and capacity for hydrogen storage in the Sc-modified C₃N₄ nanotube are thoroughly examined through the application of density functional theory (DFT). Our finding indicates that a strong coupling between the Sc-3d orbitals and N-2p orbitals stabilizes the Sc-modified C₃N₄ nanotube at a high temperature (500 K), and the high migration barrier (5.10 eV) between adjacent Sc atoms prevents the creation of metal clusters. Particularly, it has been found that each Sc-modified C₃N₄ nanotube is capable of adsorbing up to nine H₂ molecules, and the gravimetric hydrogen storage density is calculated to be 7.29 wt%. It reveals an average adsorption energy of −0.20 eV, with an estimated average desorption temperature of 258 K. This shows that a Sc-modified C₃N₄ nanotube can store hydrogen at low temperatures and harness it at room temperature, which will reduce energy consumption and protect the system from high desorption temperatures. Moreover, charge donation and reverse transfer from the Sc-3d orbital to the H-1s orbital suggest the presence of the Kubas effect between the Sc-modified C₃N₄ nanotube and H₂ molecules. We draw the conclusion that a Sc-modified C₃N₄ nanotube exhibits exceptional potential as a stable and efficient hydrogen storage substrate.

Up to now, the explanation for the origin of enhanced photocatalytic activity of N doped TiO₂ (N-TiO₂) with H incorporation, which is observed in experiment, is still lacking. In our work, the effects of hydrogenation on the stability and electronic properties of N-TiO₂ have been systematically investigated by first-principles calculations. Our results of the study on stability demonstrate that, both full and part hydrogenation could stabilize N-TiO₂ by largely reducing the formation energy of N doping under Ti-rich conditions. Moreover, the calculated results on the electronic structure show that, for the completely hydrogenated N-TiO₂, band gap becomes slightly larger, which is caused by the full passivation for unpaired electron from N atom. However, for the partially hydrogenated N-TiO₂, due to the interaction between hydrogenated and unhydrogenated N atoms, its valence band maximum shifts to higher energy by 0.32 eV and the valence band states mix with the wide band-gap states, which results in a higher light absorption capacity and carrier separation. Our results not only explain the enhancement of visible light photocatalytic activity experimentally found in N-TiO₂ specimen with H incorporation, but also indicate that, tuning the hydrogenation degree is a hopeful routine to improve the photocatalytic performance of N-TiO₂.