Conversion of Methane with Oxygen to Produce Hydrogen Catalyzed by Triatomic Rh₃^– Cluster Anion

Abstract

Metal catalysts, especially noble metals, have frequently been prepared upon downsizing from nanoparticles to subnanoclusters to catalyze the important reaction of partial oxidation of methane (POM) in order to optimize the catalytic performance and conserve metal resources. Here, benefiting from mass spectrometric experiments in conjunction with photoelectron spectroscopy and quantum chemical calculations, we successfully determine that metal cluster anions composed of only three Rh atoms (Rh 3 – ) can catalyze the POM reaction with O 2 to produce 2H 2 + CO 2 under thermal collision conditions (∼300 K). The interdependence between CH 4 and O 2 to protect Rh 3 – from collapse and to promote conversion of CH 4 → 2H 2 has been clarified. This study not only provides a promising metal cluster displaying good catalytic behavior in POM reaction under mild conditions but also reveals a strictly molecular-level mechanism of direct partial oxidation for the production of hydrogen, a promising renewable energy source in the 21st century.

Multi-active Site Dynamics on a Molecular Cr/Co/Se Cluster Catalyst

“…27,28 However, in part due to scalability challenges, the elucidation of catalytic intermediates remains challenging and relies heavily on computational modeling. 29,30 Our group introduced a family of molecular clusters, M3 (M3Co6Se8L6; M = Fe, Co, Zn, Sn; L = Ph2PNTol -), 16,[31][32][33][34] that incorporate three chemically addressable edge sites (M) on the surface of a Co/Se cluster core, a construct reminiscent of edgedoped transition metal dichalcogenide nanoflakes (Figure 1). 6,7,11 Hemilabile edge-support interactions stabilize the three edge sites in protected low-coordinate states, 31 positioning them to function as catalytically active sites and enabling the systematic study of electronic metal-support interactions, 35 as well as allosteric 34 and multi-site dynamics on the cluster surface.…”

Conversion of CH4 Catalyzed by Gas Phase Ions Containing Metals

“…The reactions of positively charged bare tantalum clusters Ta n + ( n =1‐10) and oxygen deficient Ta n O m + ( m =1 and 2) clusters with CH 4 have been systematically investigated by a cryogenic ring electrode ion trap [12k,35,45,52] . It was found that the Ta 8 O 2 + cluster has the ability to catalyze the C−C coupling of two CH 4 to generate C 2 H 6 [35] . In contrast with the reaction mechanism of aforementioned Pd 2 O + system, the interaction of Ta 8 O 2 + with the first CH 4 generated a key carbene intermediate Ta 8 O 2 (CH 2 ) + , which directly coupled with another CH 4 yielding C 2 H 6 .…”

“…cluster catalyst of Rh 3 − was characterized at room temperature [35] . By using a TOF‐MS coupled with a double ion trap apparatus including two quadrupole mass filters (QMFs) and two linear ion trap reactors (LITs) that can mass‐select product ions and spatially separate two different substrates, the detailed elementary reactions have been clarified and the importance of the order to feed the reactants to promote catalytic conversion of CH 4 →2H 2 has also been revealed.…”

“…While gas phase ions containing noble metals have good activity toward coupling of CH 4 molecules, researchers have also paid attention to ions containing non‐noble metals to find active species exhibiting comparable performance with noble metal systems. The reactions of positively charged bare tantalum clusters Ta n + ( n =1‐10) and oxygen deficient Ta n O m + ( m =1 and 2) clusters with CH 4 have been systematically investigated by a cryogenic ring electrode ion trap [12k,35,45,52] . It was found that the Ta 8 O 2 + cluster has the ability to catalyze the C−C coupling of two CH 4 to generate C 2 H 6 [35] .…”

“…With the progressive development of experimental techniques including temperature‐variable reactors, [30] high‐pressure reactors, [31] and double ion trap reactors [32] as well as the introduction of photo‐excitation [33] during 2010–2021, the identification of the thermodynamically/kinetically forbidden elementary and catalytic reactions became accessible in experiments. Furthermore, the active ions containing metals that can mediate the coupling reactions of CH 4 with oxidative molecules (e.g., O 2 , CO 2 , H 2 O) have been extended from monoatomic metals [28] to diatomic species [34] as well as homonuclear metal clusters [35] and then to heteronuclear systems [36] that have compositions closely resemble the multi‐component catalysts in condensed‐phase systems. The coupling reaction of two CH 4 molecules mediated by bare metal species, [37] homonuclear [38] and heteronuclear metal oxide clusters [39] has also been gaining increasing attention.…”