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.

Twinned Mn_0.5Cd_0.5S (T-MCS) solid solution was prepared by a hydrothermal method, and then Zn_0.76Co_0.24S/T-MCS heterojunction was fabricated by an in-situ hydrothermal method. The results show that Mn_0.5Cd_0.5S solid solutions is a twinned homojunction consisting of wurtzite Mn_0.5Cd_0.5S (WZ-MCS) and zinc-blende Mn_0.5Cd_0.5S (ZB-MCS) alternately. The introduction of Zn_0.76Co_0.24S can enhance the light harvesting ability of the system and increase the number of the surface charge carriers, the H₂ production rate of 3% Zn_0.76Co_0.24S/T-MCS reaches 132.9 mmol·g⁻¹·h⁻¹ in Na₂S/Na₂SO₃ mixture solution (300 W Xe lamp, λ > 420 nm), which is 332.2 and 1.9 times greater than those of Zn_0.76Co_0.24S and T-MCS, respectively. According to the results by energy band structure analysis, the type-II twinned homojunction between WZ-MCS and ZB-MCS can improve the bulk phase charge separation, the S-scheme heterojunction between T-MCS and Zn_0.76Co_0.24S can accelerate the interfacial charge transfer, and the REDOX capacity of the holes in T-MCS valence band and electrons in Zn_0.76Co_0.24S conduction band is retained, therefore resulting in a faster H₂ production.