Highly Efficient Reduction of Cr(VI) to Cr(III) and Cr(0) on a Self-stable p-type Cu₂WS₄ Polyhedron

Cr(VI) is a highly hazardous pollutant in the environment, its detoxication and removal are always a challenge. Herein, p-type Cu₂WS₄ photocatalyst with a regularly polyhedral structure was in-situ grown on Cu mesh and applied in photocatalytic reduction of Cr(VI). Because of the downward band bending, together with the supreme conductivity of the Cu substrate, the flowing holes migrate toward the inner space of Cu₂WS₄, and the electrons are forced to the Cu₂WS₄ surface for reducing Cr(VI) to Cr(III) and even Cr(0). S atoms set on Cu₂WS₄ lattice edges combine HCrO₄^- through an H-S bond with high affinity, enabling the efficient reduction of Cr(VI). Additionally, the redox pairs of Cu²⁺/Cu⁺, W⁶⁺/W⁴⁺ in Cu₂WS₄ consume the holes and excess electrons, realizing the self-stability and sustainability of the polyhedral Cu₂WS₄. On account of the outstanding catalytic performance and self-supported feature, the removal efficiency of Cr (VI) (30 mg/l) endowed by the resulting Cu₂WS₄/Cu mesh is increased from 19.84% at pH 5 to 98.85% at pH 1, which presents a workable approach to treating hazardous heavy metals from wastewater in a wide pH window.