Mesoporous ferrihydrite-supported Pd nanoparticles for enhanced catalytic dehalogenation of chlorinated environmental...

Organic chlorides are a group of ubiquitous environmental pollutants that have attracted wide attention because of their carcinogenetic effect on human. Catalytic hydrodechlorination represents one of the most promising methods for the removal of these contaminants, but it suffers from drawbacks such as catalytic inefficiency and/or instability, and the danger of using H₂ as hydrogen source. The relationship between the catalyst structure and its dehalogenation activity has not been completely understood. By combining the advantages of Pd nanocatalyst and mesoporous ferrihydrite (Fh) with its distinctive structure, here we present a new composite material with Pd nanoparticles (NPs) supported onto the Fh (Pd/Fh), which has excellent catalytic dehalogenation performance with a rapid, complete dechlorination of chlorophenol (turnover frequency 25.2 min^-1) and the ability to perform well over a wide range of pH and temperature. The superior catalytic property of Pd/Fh can be attributed to the three unique functions of Fh, including: 1) having abundant hydroxyl groups that provide interaction sites with metals for incorporating highly dispersed small Pd NPs; 2) facilitating the fast adsorption of chlorophenol onto the catalyst surface via hydrogen bonding and importantly, 3) working as an electron mediator to greatly enhance the electron transfer from iron or chemicals (e.g., NaBH₄) to the catalyst, thereby achieving a synergistic effect between Pd catalyst and support, and an enhanced dechlorination activity. In essence, this work presents a promising catalyst for the efficient dehalogenation of chlorinated environmental pollutants and provides an insight into the relationship between catalyst structure and dehalogenation activity.