High-efficiency purification of CH₄ and H₂ energy sources enabled by a phosphotungstic acid-supported Os single-atom catalyst

Abstract

By means of comprehensive density functional theory computations, this work proposes a novel bifunctional strategy for purifying CH4 and H2 energy sources by utilizing phosphotungstic acid-supported Os single-atom catalysts.

Near-Barrierless CO Oxidation Using Phosphotungstic Acid-Supported Single-Atom Catalysts

“…This PTA delineates four distinct oxygen atom categories, with surface oxygen atoms further segregated into terminal (O t ), bridging (O b ), and corner (O c ) configurations within the Keggin framework. A breadth of experimental and theoretical calculations converges on the consensus that the most favorable anchoring sites for metal single atoms are 4-fold hollow sites, specifically involving coordination with two surface O b atoms and two O c atoms. ,, The O t atoms, characterized by significant O t –W interactions (MBO = 1.773), are deemed catalytically inert . In contrast, the O b and O c atoms demonstrate differential catalytic propensities; the O c atoms are particularly notable for their enhanced reactivity, as indicated by the bond angle (W–O c –W = 126.57°) and bond length ( d normalW− normalO normalc = 1.932 Å, MBO ( normalW− normalO normalc ) = 0.739) compared to their O b counterparts (W–O b –W = 152.14°, d normalW − O b = 1.924 Å, and MBO ( normalW− normalO normalc ) = 0.705).…”

“…Experimental and density functional theory (DFT) studies suggest that the Pt atom in this Pt 1 /POM SAC is stabilized by a distorted square-planar geometry of oxygen atoms . Furthermore, a unique porous ammonia salt of phosphotungstic acid (PTA) has been used to create a neutral Rh 1 /PTA SAC through electrostatic interactions, with experimental techniques confirming the single atom form of Rh species for CO oxidation. , These advancements showcase the temperature-responsive catalytic activity of these SACs, with mechanisms elucidated via spectroscopy and computational studies. , The Pt 1 /PTA and Rh 1 /POM SACs have demonstrated high stability and exceptional performance in the hydrogenation of nitrobenzene, cyclohexanone, and CO oxidation. − The ability to synthesize PTA-supported metal SACs in aqueous solutions, coupled with the clear definition of catalytic sites, offers a valuable platform for understanding the relationship between the catalyst structure and performance. ,− These developments not only highlight the versatility of POMs in catalysis but also open new avenues for exploring their structural diversity in advancing SAC technology.…”

“…The critical role of solvents in selective CO oxidation has been well-established, prompting investigations into CO oxidation activities in various common solvents beyond the gas phase. 8,20 Fortunately, the solubility of POMs in both organic and aqueous solvents allows their application in a wide range of catalytic systems, enhancing both homogeneity and heterogeneity in catalysis. 31,32 In this study, we conducted a comprehensive examination of the catalytic activities of various M 1 /PTA SACs (M = Mn, Fe, Co, Ni, Ru, Rh, Pd, Re, Os, Ir, and Pt) using DFT calculations.…”

“…In light of the recent advancements in two-electron oxygen reduction reactions, which have accelerated H 2 O 2 production, − H 2 O 2 emerges as a greener and more efficient alternative to O 2 for low-temperature CO oxidation. The critical role of solvents in selective CO oxidation has been well-established, prompting investigations into CO oxidation activities in various common solvents beyond the gas phase. , Fortunately, the solubility of POMs in both organic and aqueous solvents allows their application in a wide range of catalytic systems, enhancing both homogeneity and heterogeneity in catalysis. , …”

“…Recognizing the need for CO oxidation at ambient or low temperatures, particularly in environmental purification and preferential oxidation of CO in H 2 , there arises a significant demand for strategies ensuring high reactivity at lower temperatures . Previous experimental and theoretical studies have revealed that using O 2 or N 2 O as an oxidant in CO oxidation can lead to rate-limiting steps with substantial energy barriers, ,,,,− exemplified by the Rh 1 /PTA catalyst with a barrier of 41.0 kcal/mol . In light of the recent advancements in two-electron oxygen reduction reactions, which have accelerated H 2 O 2 production, − H 2 O 2 emerges as a greener and more efficient alternative to O 2 for low-temperature CO oxidation.…”