Distance Effect of Ni-Pt Dual Sites for Active Hydrogen Transfer in Tandem Reaction

Abstract

Unveiling the distance effect between different sites in multifunctional catalysts remains a major challenge. Herein, we investigate the distance effect by constructing a dual-site distance-controlled tandem catalyst with a five-layered TiO 2 /Pt/TiO 2 /Ni/TiO 2 tubular nanostructure by template-assisted atomic layer deposition. In this catalyst, the Ni and Pt sites are separated by a porous TiO 2 interlayer, and the distance between them can be precisely controlled on the subnanometer scale by altering the thickness of the interlayer, while the inner and outer porous TiO 2 layers are designed for structural stability. The catalyst exhibits superior performance for the tandem hydrazine hydrate decomposition to hydrogen and subsequent nitrobenzene hydrogenation when the Ni and Pt site distance is on the subnanometer level. The performance increases with the decrease of the distance and is better than the catalyst without the TiO 2 interlayer. Isotopic and kinetic experiments reveal that the distance effect controls the transfer of active hydrogen, which is the rate-determining step of the tandem reaction in a water solvent. Reduced Ti species with oxygen vacancies on the TiO 2 interlayer provide the active sites for hydrogen transfer with -Ti-OH surface intermediates via the continuous chemisorption/desorption of water. A smaller distance induces the generation of more active sites for hydrogen transfer and thus higher efficiency in the synergy of Ni and Pt sites. Our work provides new insight for the distance effect of different active sites and the mechanism of intermediate transfer in tandem reactions.

Selective Hydrogenolysis of Erythritol over Ir−ReOx/Rutile‐TiO2 Catalyst

“…The TiO 2 ‐supported catalyst also showed higher selectivity toward dideoxygenation of 1,2,3‐triol to 1‐alcohol, probably by the rapid overhydrogenolysis of adsorbed diols before desorption. These two characters can be explained by the larger steric hinderance around the active site to decrease the rate and equilibrium constant of adsorption (Figure 3), although there may be other reasons for higher dideoxygenation activity such as high concentration of active hydrogen species caused by the efficient supply from many nearby Ir particles [36,37] . Another characteristic of Ir−ReO x /TiO 2 was the smaller activity increase above Ir−ReO x /SiO 2 in hydrogenolysis of mono‐ols and 1‐position of polyols than that of 2‐ and 3‐positions of polyols.…”

“…These two characters can be explained by the larger steric hinderance around the active site to decrease the rate and equilibrium constant of adsorption (Figure 3), although there may be other reasons for higher dideoxygenation activity such as high concentration of active hydrogen species caused by the efficient supply from many nearby Ir particles. [36,37] Another characteristic of IrÀ ReO x /TiO 2 was the smaller activity increase above IrÀ ReO x /SiO 2 in hydrogenolysis of mono-ols and 1-position of polyols than that of 2-and 3positions of polyols. Some of IrÀ ReOH interface sites in IrÀ ReO x / TiO 2 might not have activity in hydrogenolysis of mono-ols.…”

Magnetocatalysis: The Interplay between the Magnetic Field and Electrocatalysis

“…[7][8][9][10] In contrast to tools such as high pressure and high temperature that require critical experiment conditions, a commercial permanent magnet is enough to influence many chemical reactions. [11,12] For example, an extremely low magnetic field of 55 mT (600 times the magnetic field of earth) can accelerate the catalytic ATP synthesis by 50%. [13] Recently, there has been growing research interest regarding the effects of magnetic interactions on the rate of hydrogen-energy-related reactions such as in water splitting and fuel cells (Figure 1a).…”

Dual metal nanoparticles within multicompartmentalized mesoporous organosilicas for efficient sequential hydrogenation

“…For example, core-shell nanostructures were employed to spatially isolate two metal NPs within the core or on the outer shell for CO 2 hydrogenation 20 – 25 . Similarly, TiO 2 nanotubes were reported to localize Pt and Ni NPs on their outer or inner surfaces using atomic layer deposition for transfer hydrogenation 26 – 28 . Hierarchical porous silicas were also used to position dual metal NPs through stepwise modification of their pore surfaces for sequential oxidation of cinnamyl alcohol 29 , 30 .…”

“…Hierarchical porous silicas were also used to position dual metal NPs through stepwise modification of their pore surfaces for sequential oxidation of cinnamyl alcohol 29 , 30 . Despite the great success in constructing cascade catalysts via such spatial separation of multiple metal NPs, these existing materials either lack compartmentalized structures to accommodate metal NPs on the outer surfaces 20 – 28 , or else are unable to provide well-defined nanochannels for connecting different metal NPs in nanoscale proximity 26 – 30 . The unsatisfactory integration of all the desired features in a single catalyst hinders realization of efficient synergistic catalysis.…”