In situ tuning of electronic structure of catalysts using controllable hydrogen spillover for enhanced selectivity

Abstract

In situ tuning of the electronic structure of active sites is a long-standing challenge. Herein, we propose a strategy by controlling the hydrogen spillover distance to in situ tune the electronic structure. The strategy is demonstrated to be feasible with the assistance of CoOx/Al2O3/Pt catalysts prepared by atomic layer deposition in which CoOx and Pt nanoparticles are separated by hollow Al2O3 nanotubes. The strength of hydrogen spillover from Pt to CoOx can be precisely tailored by varying the Al2O3 thickness. Using CoOx/Al2O3 catalyzed styrene epoxidation as an example, the CoOx/Al2O3/Pt with 7 nm Al2O3 layer exhibits greatly enhanced selectivity (from 74.3% to 94.8%) when H2 is added. The enhanced selectivity is attributed to the introduction of controllable hydrogen spillover, resulting in the reduction of CoOx during the reaction. Our method is also effective for the epoxidation of styrene derivatives. We anticipate this method is a general strategy for other reactions.

Hydrogen spillover in complex oxide multifunctional sites improves acidic hydrogen evolution electrocatalysis

“…In order to provide the evidences of possible atomic-scale hydrogen spillover in La 2 Sr 2 PtO 7+δ for acidic HER electrocatalysis, comprehensive experiments and electrochemical measurements were performed. The hydrogen spillover could be initially confirmed by the color change in the mixture of the catalyst and WO 3 52 . As seen from Supplementary Fig.…”

“…In view of the steadily weakened H adsorption, a feasible channel for the hydrogen spillover from O site → La-Pt bridge site → Pt site may be formed on the La 2 Sr 2 PtO 7+δ catalyst. Noticeably, the interface-free feature and short reaction distance within the crystal lattice on single-phase La 2 Sr 2 PtO 7+δ catalyst is beneficial for minimizing the kinetic barrier for hydrogen spillover 52 , 67 , somewhat analogous to the reported metal alloy system with low hydrogen spillover barrier 68 – 71 . The calculation shows that the hydrogen spillover step has a low energy barrier value of 0.22 eV (Fig.…”

“…19 , The WO 3 after HER test exhibits an unchanged color. However, the mixture of La 2 Sr 2 PtO 7+δ and WO 3 after HER test generates a dark blue color, which is because that the spilled-over hydrogen migrates and readily reacts with WO 3 to form dark blue H x WO 3 52 , 53 . Besides, the hydrogen spillover effect could be also verified by Tafel slope and pH-dependent HER experiments.…”

Exceptional hydrogen evolution in acid enabled by a multi-function-site complex oxide via atomic-scale hydrogen spillover

“…5c). Noticeable, the interface-free feature and short reaction distance within the crystal lattice on singlephase La 2 Sr 2 PtO 7+δ catalyst is bene cial for minimizing the kinetic barrier for hydrogen spillover 52,53 , somewhat analogous to the reported metal alloy system with low hydrogen spillover barrier [54][55][56][57] . Based on these DFT results, a possible HER catalytic mechanism on La 2 Sr 2 PtO 7+δ in acidic media via multifunction catalytic sites induced atomic-scale hydrogen spillover was proposed, as schematically illustrated in Fig.…”

Hydrogen spillover and its relation to catalysis: observations on structurally defined single-atom sites

“…5,23,24 Understanding the impact of hydrogen spillover on the electronic structure of the catalyst as well as its hydrogenation activity might have implications for reactions that do not involve H atom transfer directly but which may either form H species as side-product or benefit from the cofeeding of H2 such as shown recently for epoxidation reactions. 25 For reactions like the CO2 or N2 hydrogenation, the contribution of hydrogen spillover to catalysis has been vividly discussed recently. [26][27][28][29] Based on our results, it is very likely that hydrogen spillover plays a crucial role in forming oxygen vacancies and transferring H to polar molecules like CO2.…”