Indium-decorated Pd nanocubes degrade nitrate anions rapidly

Indium-decorated palladium nanoparticles (In-on-PdNPs) are active for room-temperature catalytic reduction of aqueous nitrate, where the active sites are metallic In atoms on the Pd surface. The PdNPs are pseudo-spherical in shape, and it is unclear if their faceted nature plays a role in nitrate reduction. We synthesized different-sized, cube-shaped NPs with differing In coverages (sc%), and studied the resultant In-on-Pd-nanocubes (NCs) for nitrate reduction. The NCs exhibited volcano-shape activity dependence on In sc%, with peak activity around 65–75 sc%. When rate constants were normalized to undercoordinated atoms (at edge + corners), the NCs exhibited near-identical maximum activity (20×-higher than In-on-PdNPs) at ρIn/Pd edge+corner ∼0.5 (∼5 In atoms per 10 edge and corner atoms). NCs with a higher In edge + corner density (ρIn/Pd edge+corner ∼1.5) were less active but did not generate NH4+ at nitrate conversions tested up to 36 %. Edge-decorated cubes may be the structural basis of improved bimetallic catalytic denitrification of water

Integration of daytime radiative cooling and solar heating

Summary: In recent years, sustainable energy development has become a major theme of research. The combination of solar heating and daytime radiative cooling has the potential to build a competitive strategy to alleviate current environmental and energy problems. Several studies on the combination of daytime radiative cooling and solar heating have been reported to improve energy utilization efficiency. However, most integrations still have a low solar/mid-infrared spectrum regulation range, low heating/cooling performance, and poor stability. To promote this technology further for real-world applications, herein we summarize the latest progress, technical features, bottlenecks, and future opportunities for the current integration of daytime radiative cooling and solar heating through the switch mode (including electrical, thermal-responsive, and mechanical regulations) and collaborative mode

Indium-decorated Pd nanocubes degrade nitrate anions rapidly

Indium-decorated palladium nanoparticles (In-on-PdNPs) are active for room-temperature catalytic reduction of aqueous nitrate, where the active sites are metallic In atoms on the Pd surface. The PdNPs are pseudo-spherical in shape, and it is unclear if their faceted nature plays a role in nitrate reduction. We synthesized different-sized, cube-shaped NPs with differing In coverages (sc%), and studied the resultant In-on-Pd-nanocubes (NCs) for nitrate reduction. The NCs exhibited volcano-shape activity dependence on In sc%, with peak activity around 65-75 sc%. When rate constants were normalized to undercoordinated atoms (at edge+corners), the NCs exhibited near-identical maximum activity (20×-higher than In-on-PdNPs) at ρIn/Pd edge+corner ~0.5 (~5 In atoms per 10 edge and corner atoms). NCs with a higher In edge+corner density (ρIn/Pd edge+corner ~1.5) were less active but did not generate NH4+ at nitrate conversions tested up to 36%. Edge-decorated cubes may be the structural basis of improved bimetallic catalytic denitrification of water

Insights into Nitrate Reduction over Indium-Decorated Palladium Nanoparticle Catalysts

Nitrate (NO₃⁻) is an ubiquitous groundwater contaminant and is detrimental to human health. Bimetallic palladium-based catalysts have been found to be promising for treating nitrate (and nitrite, NO₂⁻) contaminated waters. Those containing indium (In) are unusually active, but the mechanistic explanation for catalyst performance remains largely unproven. We report that In deposited on Pd nanoparticles (NPs) (“In-on-Pd NPs”) shows room-temperature nitrate catalytic reduction activity that varies with volcano-shape dependence on In surface coverage. The most active catalyst had an In surface coverage of 40%, with a pseudo-first order normalized rate constant of <i>k</i>_cat ∼ 7.6 L g_{surface-metal}⁻¹ min⁻¹, whereas monometallic Pd NPs and In₂O₃ have nondetectible activity for nitrate reduction. X-ray absorption spectroscopy (XAS) results indicated that In is in oxidized form in the as-synthesized catalyst; it reduces to zerovalent metal in the presence of H₂ and reoxidizes following NO₃⁻ contact. Selectivity in excess of 95% to nontoxic N₂ was observed for all the catalysts. Density functional theory (DFT) simulations suggest that submonolayer coverage amounts of metallic In provide strong binding sites for nitrate adsorption and they lower the activation barrier for the nitrate-to-nitrite reduction step. This improved understanding of the In active site expands the prospects of improved denitrification using metal-on-metal catalysts