Au^δ−–O_v–Ti³⁺ Interfacial Site: Catalytic Active Center toward Low-Temperature Water Gas Shift Reaction

Abstract

The electronic metal–support interaction (EMSI) plays a crucial role in promoting catalytic performance toward interface electronic structure sensitive reactions, such as the low temperature water gas shift reaction (LT-WGSR). Herein, a mixed metal oxide support (ZnTi-MMO) was obtained via structural topological transformation from a zinc–titanium layered double hydroxides (ZnTi-LDHs) precursor, which was used for the immobilization of Au nanoparticles (NPs). Following a reduction pretreatment at 300 °C in a H2 atmosphere, the resulting optimal catalyst Au@TiO2–x /ZnO­(H300) exhibits a WGSR rate up to 0.15 molco molAu –1 s–1, which is at a high level compared with previously reported gold-based catalyst systems. Ac-HAADF-STEM combined with CO pulse chemisorption measurements verifies a TiO2–x overlayer on the surface of Au NPs. Quasi in situ XPS, EPR, in situ EXAFS, and in situ DRIFTS demonstrate the formation of interface dual-active-site (Auδ−–Ov–Ti3+; Ov: oxygen vacancy) based on electron transfer from the TiO2–x overlayer to Au atoms, in which the electron-enriched Auδ− species enhance CO chemisorption while Ov–Ti3+ accelerates the dissociation of the H2O molecule, accounting for the largely enhanced catalytic activity and stability of Au@TiO2–x /ZnO­(H300) compared with the traditional Au/TiO2 system. In situ/operando EXAFS further confirms that Auδ−–Ov–Ti3+ interfacial site serves as the optimal active site toward WGSR: both Auδ− species and Ov directly participate in the rate-determining step of LT-WGSR (water dissociation). The discovery and identification of the interfacial active site in this system can be extended to other metal catalysts with largely promoted performance in heterogeneous catalysis.

Catalytic Semi‐Water–Gas Shift Reaction: A Simple Green Path to Formic Acid Fuel

“…In these cases, formiate is the most abundant experimentally observed intermediate because its formation barrier is lower than its dissociation barrier. However, it is difficult to desorb it from the catalyst surface . Ruthenium complexes supported in SILPs have also presented higher activation energies (41–84 kJ mol −1 ) in the WGSR .…”

“…However,i ti sd ifficult to desorb it from the catalyst surface. [56][57][58][59][60][61] Ruthenium complexes supported in SILPs have also presentedh igher activation energies (41-84 kJ mol À1 )i nt he WGSR. [31,32,62] Of note, neither of these catalytic systems were able to yield FA.…”

Glycerol aerobic oxidation to glyceric acid over Pt/hydrotalcite catalysts at room temperature

“…The direct catalytic oxidation of glycerol to GLYA has been studied for decades, and Pt-based catalysts have shown satisfactory behavior for GLYA generation [20,21]. In attaining a single product selectively with a high conversion meanwhile, support effect should be taken as priority, since metal-support interaction plays a vital role in heterogeneous catalysis [22,23]. For instance, Yu and co-workers [24] reported an efficient N-doped carbon supported Pt catalyst for aerobic oxidation of glycerol, where nitrogen dopant obviously improved the dispersion of Pt NPs with enhanced metal-support interaction and promoted catalytic performance.…”

Recent In Situ/Operando Spectroscopy Studies of Heterogeneous Catalysis with Reducible Metal Oxides as Supports

“…These results show the efficiency of in situ spectroscopy methodology in monitoring the structural and electronic dynamic evolution of metal-support interfacial sites. Recently, EMSI was also proven to exist in Au@TiO 2−x catalysts [56]. In situ EXAFS proves that the metal support interfacial site is the active site for WGSR.…”