Intense Visible-Light Absorption in SrRuO₃/C₃N₄ Heterostructures for the Highly Efficient Reduction of Hg(II)

Strontium ruthenium oxide (SrRuO₃) is recognized as a metallic itinerant ferromagnet and utilized as a conducting electrode in heterostructure oxides with unforeseen optical characteristics, including remarkably low-reflection and high-absorption visible-light spectrum compared to classical metals. By coupling mesoporous SrRuO₃ nanoparticles (NPs) with porous g-C₃N₄ nanosheets for the first time, we evidence remarkably promoted visible light absorption and superior photocatalytic performances for Hg(II) reduction under illumination with visible light. The photocatalytic performance of g-C₃N₄ increased upon boosting the SrRuO₃ percentage to 1.5%, and this (1.5% SrRuO₃/g-C₃N₄ heterostructure) is considered the optimum condition to obtain a high photocatalytic efficiency of about 100% within 50 min. It was promoted 3.68 and 5.75 times compared to SrRuO₃ and g-C₃N₄, respectively. Also, a Hg(II) reduction rate of 1.5% SrRuO₃/g-C₃N₄ was enhanced3.84- and 6.28-fold than those of pure SrRuO₃ NPs and g-C₃N₄, respectively. Such a high photocatalytic performance over SrRuO₃/g-C₃N₄ photocatalysts was explained by the characteristics of SrRuO₃ NPs incorporated on porous g-C₃N₄ layers, which demonstrate strong absorption of visible light with a narrow band gap, a large photocurrent density of ∼9.07 mA/cm², well-dispersed and small particle sizes, and cause facile diffusion of HCOOH and Hg(II) ions and electrons. The present work provides a dramatic novel approach to the challenge of constructing visible-light photosensitive photocatalysts for wastewater remediation.