Red phosphorus (RP), as a promising non-metallic photocatalyst, has garnered considerable attention due to its unique structural characteristics and exceptional optoelectronic properties. While previous reviews have explored RP-based photocatalysis, recent advancements in fabrication strategies, characterization techniques, and theoretical modeling have significantly reshaped the design, synthesis, and optimization of these materials. This review provides a comprehensive and critical evaluation of the latest progress in RP-based photocatalysts over the past five years, with a particular focus on strategies aimed at enhancing light harvesting capabilities, improving the separation and transport of photogenerated charge carriers, and ensuring long-term stability. Particular emphasis is placed on the role of innovative in-situ characterization techniques and density functional theory (DFT) simulations in elucidating the underlying photocatalytic mechanism across diverse applications, including photocatalytic hydrogen evolution, CO₂ reduction, bacterial disinfection and organic pollutant degradation. Finally, this review highlights emerging challenges and forward-looking strategies to further boost the photocatalytic performance of RP-based systems, offering valuable insights for the rational design of next-generation non-metallic photocatalysts.

Graphdiyne (GD) is one of carbon allotropes with the unique structure and has ideal high strength, excellent light transmittance, electrical conductivity, high carrier mobility, and thermal conductivity. GD with a natural band gap is an intrinsic semiconductor with special charge transport properties. GD shows a band gap in the range of 0.45 to 1.30 eV, compared with graphene without band gap, which has a promising potential for electronic, catalytic, optical and mechanical applications. Also, GD has two different Dirac cones near the top and bottom of the Fermi energy level, indicating that GD is a self-doped semiconductor with charge carriers and does not require additional doping like graphene. GD can be used as a potential and excellent photocatalytic material, and theoretically it is needed to be modified to build active sites for efficient photo-induced reactions.

The solid lubricant MoS₂ demonstrates excellent lubricating properties, but it spontaneously oxidizes and absorbs moisture in air, and thus results in poor wear resistance and short wear-life. In this study, the additive g-C₃N₄ (CN) was successfully combined with MoS₂ via hydrothermal synthesis as a solid lubricant for the first time. Meanwhile, a low friction coefficient (COF, μ = 0.031) and ultra-long wear-life of CN/MoS₂ compared to pure MoS₂ in air were demonstrated. The functional groups and good crystallinity of the lubricant material were characterized via Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The formed valence states in CN/MoS₂ were analyzed via X-ray photoelectron spectroscopy (XPS). The characterized results of the scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) show the morphology and interior crystal phase structure of CN/MoS₂. From the cross-section analysis, the presence of iron oxide nanoparticles lubricating film is synergistic with CN/MoS₂ film during the friction process, resulting in its ultra-long wear-life. In particular, the friction mechanism of interlayer sliding friction combined with energy storage friction was analyzed and proposed.