Photocatalytic splitting of hydrogen sulfide (H 2 S) for hydrogen evolution is a promising method to solve the energy and environmental issues. In this work, S,N-codoped carbon dots (S,N-CDs)/graphitic carbon nitride (g-C 3 N 4 ) nanosheet is synthesized by hydrothermal method as an efficient photocatalyst for the decomposition of H 2 S. In addition to the characterization of the morphology and structure, chemical state, optical and electrochemical performances of S,N-CDs/g-C 3 N 4 , hydrogen evolution tests show that the activity of g-C 3 N 4 is improved by introducing S,N-CDs, and the enhancement depends strongly on the wavelength of incident light. The photocatalytic hydrogen production rate of S,N-CDs/g-C 3 N 4 composite reaches 832 μmol g −1 h −1 , which is 38 times to that of g-C 3 N 4 under irradiation at 460 nm. Density functional theory calculations and electron paramagnetic resonance as well as photoluminescence technologies have altogether authenticated that the unique wavelength-dependent photosensitization of S,N-CDs on g-C 3 N 4 ; meanwhile, a good match between the energy level of S,N-CDs and g-C 3 N 4 is pivotal for the effective photocatalytic activity. Our work has unveiled the detailed mechanism of the photocatalytic activity enhancement in S,N-CDs/g-C 3 N 4 composite and showed its potential in photocatalytic splitting of H 2 S for hydrogen evolution.
Due to the excellent electrical and optical properties and their integration capability without lattice matching requirements, low-dimensional materials have received increasing attention in silicon photonic circuits. Bi2O2Se with high carrier mobility, narrow bandgap, and good air stability is very promising for high-performance near-infrared photodetectors. Here, the chemical vapor deposition method is applied to grow Bi2O2Se onto mica, and our developed polycarbonate/polydimethylsiloxane-assisted transfer method enables the clean and intact transfer of Bi2O2Se on top of a silicon waveguide. We demonstrated the Bi2O2Se/Si waveguide integrated photodetector with a small dark current of 72.9 nA, high responsivity of 3.5 A·W–1, fast rise/decay times of 22/78 ns, and low noise-equivalent power of 15.1 pW·Hz–0.5 at an applied voltage of 2 V in the O-band for transverse electric modes. Additionally, a microring resonator is designed for enhancing light–matter interaction, resulting in a wavelength-sensitive photodetector with reduced dark current (15.3 nA at 2 V) and more than a 3-fold enhancement in responsivity at the resonance wavelength, which is suitable for spectrally resolved applications. These results promote the integration of Bi2O2Se with a silicon photonic platform and are expected to accelerate the future use of integrated photodetectors in spectroscopy, sensing, and communication applications.
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