Improved Prediction of Nanoalloy Structures by the Explicit Inclusion of Adsorbates in Cluster Expansions

Density functional theory (DFT) is widely used to predict the properties of materials, but its direct application to nanomaterials of experimentally relevant size can be prohibitively expensive. It has previously been demonstrated that this problem can be addressed through the generation of cluster expansion models trained on DFT calculations. Here, we evaluate the use of the cluster expansion method to calculate the structures of bimetallic Pt–Cu nanoparticles of varying sizes and compositions and in different chemical environments. The predicted surface composition, shape, and lattice parameters of the alloy nanoparticles are found to be in good agreement with experimental characterization. We demonstrate that, to account for adsorbate-induced surface segregation, the best agreement for surface composition can be achieved by constructing a novel cluster expansion for alloy nanoparticles of varying shapes and sizes that explicitly includes adsorbed oxygen

Recovery of Inorganic Phosphorus Using Copper-Substituted ZSM‑5

Efficient and cost-effective separation of phosphorus (P) from aqueous solutions possesses great value in addressing the challenges in sustainability. Not only does it mitigate the pollution caused by phosphate in agricultural runoffs, but it also provides a renewable source for production of phosphorus-based chemicals and fertilizes. Here we report on the use of copper-substituted zeolites, Cu-ZSM-5, as sorbents for recovery of P. Fast capture and release of phosphate anions are demonstrated with >90% efficiency of recovery using synthetic solutions of Na₂HPO₄ and NaCl, respectively. The zeolite sorbents are also found to be recyclable and sustain high recovery efficiencies after multiple capture–release cycles. Cu­(II) species in the zeolites are identified to be the active sites for anion adsorption, and based on this finding a ligand exchange mechanism is proposed for the capture and release of phosphorus

Resolving the Oxygen Species on Ozone Activated AgAu Alloy Catalysts for Oxidative Methanol Coupling

Bimetallic alloy catalysts frequently demonstrate distinct performances that are superior to their monometallic counterparts, yet their surface chemistry needs to be carefully studied to understand their structure–activity relationships. The nanoporous Ag0.03Au0.97 alloy catalyst becomes highly active and selective for oxidative methanol coupling to methyl formate after O3 activation. HS-LEIS reveals the O3 treatment results in enrichment of Ag (>30%) on the outermost surface layer, while oxygen treatment additionally leads to segregation of a larger portion of Cu impurity on the surface. A series of characteristic Raman bands at 395, 577, 867, and 904 cm–1 only form under oxidative methanol coupling reaction on O3-activated AgAu catalyst. These bands correspond to Ag3–O* (395 cm–1), M–O* on O–Au(111) and AgAu alloy (577 cm–1), CH3OH* (867 cm–1), and HOOH* (904 cm–1), as revealed by DFT calculations. The cyclic in situ Raman and reactivity studies indicate the detected oxygen species could be related to a “memory effect” of the catalyst upon pretreatment. The current study highlights the importance of applying surface-specific techniques for investigation of compositions of outermost surface layers of alloy catalysts, as well as integration of in situ spectroscopies and computational investigations for understanding surface structures at the molecular level under reaction conditions