Violet phosphorus quantum dots as an emerging visible light-responsive photocatalyst for an efficient hydrogen evolution reaction

The development of visible light-responsive semiconductor photocatalysts has inspired extensive interest, but the number is very limited for the quantum dot (QD)-based ones. Herein, an emerging mono-elemental material, violet phosphorus (VP) QDs, was synthesized via liquid-phase exfoliation, whose lateral size and thickness could be tuned by varying the centrifugation speed. The VPQDs show a bandgap of 2.06 eV with potentials of conduction and valence bands straddled for the water reduction and oxidation, and the longitudinal destruction of VP exposes abundant surface active sites. More importantly, the VPQDs exhibit rapid photogenerated charge mobility and improved charge separation efficiency after loading with a Rh cocatalyst. Consequently, we give the first demonstration that the VPQDs as a novel 600 nm-class photocatalyst are active for H₂ evolution under visible light irradiation, showing activities of approximately 18 and 80 times greater than that of bulk VP and black phosphorus QDs, and delivering an apparent quantum yield of 2.86% at 475 nm. To our knowledge, the photocatalytic H₂ evolution rate of 3325.1 μmol h⁻¹ g⁻¹ observed on the VPQDs in this work should be the highest among all the mono-elemental-based photocatalysts.