Rational design via surface engineering on dual 2-dimensional ZnSe/g-C3N4 heterojunction for efficient sequestration of elemental mercury

Abstract

The rational structural design and regulation of heterojunction catalyst are crucial and still challenging for improving its catalytic activity and environmental friendliness. Herein, one novel dual 2-dimensional ZnSe/g-C3N4 (ZSCN) nano-heterojunction was developed by a newly designed incipient wetness impregnation method followed by in-situ selenization, which was used at the first time for future remediation of Hg0 pollution derived from coal combustion. The as-synthesized ZnSe/g-C3N4 exhibited unparalleled performance toward Hg0 immobilization under harsh experimental conditions. The coupling between g-C3N4 with ZnSe can significantly enhance its Hg0 removal performance, and the enhanced Hg0 adsorption capacity in the case of the 20ZSCN reached up to 16.59 mg·g−1, 4 times higher than 20ZSCN(mix) prepared by simple mechanical mixing. The phenomenon was attributed to the high active sites exposure rate and effective electronic transport on the heterostructure interface, which was confirmed by the density functional theory analysis. The Se2- on ZSCN surface act as the main activity center for the oxidization from Hg0 to Hg2+, and further sequestration in forms of stable HgSe. This work offers a new avenue for the rational design of a novel ZnSe/g-C3N4 2d-heterojunction catalyst with high stability and long durability in the immobilization of highly toxic Hg0 through surface engineering.