Search

Chlorate (ClO3-) is a common water pollutant due to its gigantic scale of production, wide applications in agriculture and industry, and formation as a toxic byproduct in various water treatment processes. This work reports on the facile preparation, mechanistic elucidation, and kinetic evaluation of a bimetallic catalyst for highly active ClO3- reduction into Cl-. Under 1 atm H2 and 20 °C, PdII and RuIII were sequentially adsorbed and reduced on a powdered activated carbon support, affording Ru0-Pd0/C from scratch within only 20 min. The Pd0 particles significantly accelerated the reductive immobilization of RuIII as >55% dispersed Ru0 outside Pd0. At pH 7, Ru-Pd/C shows a substantially higher activity of ClO3- reduction (initial turnover frequency >13.9 min-1 on Ru0; rate constant at 4050 L h-1 gmetal-1) than reported catalysts (e.g., Rh/C, Ir/C, Mo-Pd/C) and the monometallic Ru/C. In particular, Ru-Pd/C accomplished the reduction of concentrated 100 mM ClO3- (turnover number > 11,970), whereas Ru/C was quickly deactivated. In the bimetallic synergy, Ru0 rapidly reduces ClO3- while Pd0 scavenges the Ru-passivating ClO2- and restores Ru0. This work demonstrates a simple and effective design for heterogeneous catalysts tailored for emerging water treatment needs.

Adding CrIII or AlIII salts into the water suspension of platinum group metal (PGM) catalysts accelerated oxyanion pollutant reduction by up to 600%. Our initial attempts of adding K2CrVIO4, K2CrVI2O7, or KCrIII(SO4)2 into Pd/C enhanced BrO3- reduction with 1 atm H2 by 6-fold. Instrument characterizations and kinetic explorations collectively confirmed the immobilization of reduced CrVI as CrIII(OH)3 on the catalyst surface. This process altered the ζ-potentials from negative to positive, thus substantially enhancing the Langmuir-Hinshelwood adsorption equilibrium constant for BrO3- onto Pd/C by 37-fold. Adding AlIII(OH)3 from alum at pH 7 achieved similar enhancements. The Cr-Pd/C and Al-Pd/C showed top-tier efficiency of catalytic performance (normalized with Pd dosage) among all the reported Pd catalysts on conventional and nanostructured support materials. The strategy of adding inert metal hydroxides works for diverse PGMs (palladium and rhodium), substrates (BrO3- and ClO3-), and support materials (carbon, alumina, and silica). This work shows a simple, inexpensive, and effective example of enhancing catalyst activity and saving PGMs for environmental applications.

Constructing single atom catalysts with fine-tuned coordination environments can be a promising strategy to achieve satisfactory catalytic performance. Herein, via a simple calcination temperature-control strategy, CeO2 supported Pt single atom catalysts with precisely controlled coordination environments are successfully fabricated. The joint experimental and theoretical analysis reveals that the Pt single atoms on Pt1/CeO2 prepared at 550 °C (Pt/CeO2-550) are mainly located at the edge sites of CeO2 with a Pt-O coordination number of ca. 5, while those prepared at 800 °C (Pt/CeO2-800) are predominantly located at distorted Ce substitution sites on CeO2 terrace with a Pt-O coordination number of ca. 4. Pt/CeO2-550 and Pt/CeO2-800 with different Pt1-CeO2 coordination environments exhibit a reversal of activity trend in CO oxidation and NH3 oxidation due to their different privileges in reactants activation and H2O desorption, suggesting that the catalytic performance of Pt single atom catalysts in different target reactions can be maximized by optimizing their local coordination structures.

Non-precious metal catalysts with enhanced low-temperature activity and improved water resistance are highly demanded for emission control. CuO-based catalysts are promising alternatives to precious metal catalysts due to their acceptable activity and cost-effectiveness. However, there is an urgent need to further enhance their low-temperature activity and water resistance for industrial applications. Herein, CuO catalysts supported by various SiO2-TiO2 supports were prepared and evaluated for CO oxidation and NO reduction by CO reactions under the testing conditions with and without water. Among the studied catalysts with different SiO2 contents, CuO/5SiO2-TiO2, in which CuO was supported by SiO2-TiO2 with 5 wt.% SiO2, exhibited the best performance for CO oxidation. Compared with CuO/TiO2 and CuO/SiO2 reference catalysts, the CuO/5SiO2-TiO2 catalyst showed enhanced catalytic activity in both CO oxidation and NO reduction by CO under dry and wet conditions. Comprehensive characterizations revealed that the presence of SiO2 in TiO2 support facilitated the CuO/5SiO2-TiO2 catalyst with a high dispersion and reduced oxidation states of CuOx species. This not only improved the low-temperature reducibility but also enhanced the adsorption of reactive CO species. As a result, the CuO/5SiO2-TiO2 catalyst demonstrated superior catalytic activity. Furthermore, the inclusion of SiO2 in the catalyst inhibited H2O adsorption, contributing to the enhanced water resistance on CuO/5SiO2-TiO2 catalyst. These advantages in catalytic activity and water resistance make CuO/5SiO2-TiO2 a promising candidate for applications in emission control. [ABSTRACT FROM AUTHOR]

Non-precious metal catalysts with enhanced low-temperature activity and improved water resistance are highly demanded for emission control. CuO-based catalysts are promising alternatives to precious metal catalysts due to their acceptable activity and cost-effectiveness. However, there is an urgent need to further enhance their low-temperature activity and water resistance for industrial applications. Herein, CuO catalysts supported by various SiO2-TiO2 supports were prepared and evaluated for CO oxidation and NO reduction by CO reactions under the testing conditions with and without water. Among the studied catalysts with different SiO2 contents, CuO/5SiO2-TiO2, in which CuO was supported by SiO2-TiO2 with 5 wt.% SiO2, exhibited the best performance for CO oxidation. Compared with CuO/TiO2 and CuO/SiO2 reference catalysts, the CuO/5SiO2-TiO2 catalyst showed enhanced catalytic activity in both CO oxidation and NO reduction by CO under dry and wet conditions. Comprehensive characterizations revealed that the presence of SiO2 in TiO2 support facilitated the CuO/5SiO2-TiO2 catalyst with a high dispersion and reduced oxidation states of CuOx species. This not only improved the low-temperature reducibility but also enhanced the adsorption of reactive CO species. As a result, the CuO/5SiO2-TiO2 catalyst demonstrated superior catalytic activity. Furthermore, the inclusion of SiO2 in the catalyst inhibited H2O adsorption, contributing to the enhanced water resistance on CuO/5SiO2-TiO2 catalyst. These advantages in catalytic activity and water resistance make CuO/5SiO2-TiO2 a promising candidate for applications in emission control. [ABSTRACT FROM AUTHOR]

Indium nitride (InN) is a promising photoelectrode material for photoelectrochemical (PEC) water splitting due to its strong light absorption capability, excellent electron mobility and direct band gap. However, the severe re-joining of the carrier in bulk or surface hinders the application of InN nanomaterials. Therefore, an InN nanorod/Ni(OH)2 heterojunction for PEC water splitting with enhanced interfacial charge transfer under a biased voltage was constructed first. In this case, the Ni(OH)2 catalyst not only has excellent electrocatalytic properties, but also can eliminate the surface state of the InN nanorods within a certain range. The improved InN/Ni(OH)2 photoelectrodes show that the photocurrent density of 4.43 mA cm−2, was 16 times higher than that of the pure InN nanorods (0.27 mA cm−2) at the same potential. Its applied bias photon-to-current efficiency (ABPE) at 0.92 V vs. Ag/AgCl was 6.92% with a 43-fold increase when compared to InN (0.16%). The work reported here, supplies practical and effective ideas to construct an InN-based nanorod heterojunction, thereby enhancing the redox reaction dynamics of the PEC water splitting in alkaline pH electrolyte. [ABSTRACT FROM AUTHOR]