HCl-Tolerant H_<i>x</i>PO₄/RuO_<i>x</i>–CeO₂ Catalysts for Extremely Efficient Catalytic Elimination of Chlorinated VOCs

Abstract

Bulk metal doping and surface phosphate modification were synergically adopted in a rational design to upgrade the CeO₂ catalyst, which is highly active but easily deactivated for the catalytic oxidation of chlorinated volatile organic compounds (Cl-VOCs). The metal doping increased the redox ability and defect sites of CeO₂, which mostly promoted catalytic activity and inhibited the formation of dechlorinated byproducts but generated polychlorinated byproducts. The subsequent surface modification of the metal-doped CeO₂ catalysts with nonmetallic phosphate completely suppressed the formation of polychlorinated byproducts and, more importantly, enhanced the stability of the surface structure by forming a chainmail layer. A highly active, durable, and selective catalyst of phosphate-functionalized RuO_<i>x</i>-CeO₂ was the most promising among all the metal-doped (Ru, Pd, Pt, Cr, Mn, Fe, Co, and Cu) CeO₂ catalysts investigated owing to the prominent chemical stability of RuO_<i>x</i> and its superior versatility in the catalytic oxidation of different kinds of Cl-VOCs and other typical pollutants, including dimethyl sulfide, CO, and C₃H₈. Moreover, the chemical stability of the catalyst, including its bulk and surface structural stability, was investigated by combining intensive treatment with HCl/H₂O or HCl with subsequent ex situ ultraviolet-visible light Raman spectroscopy and confirmed the superior resistance to Cl poisoning of the phosphate-functionalized RuO_<i>x</i>-CeO₂. This work exemplifies a promising strategy for developing ideal catalysts for the removal of Cl-VOCs and provides a catalyst with the superior catalytic performance in Cl-VOC oxidation to date.