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The elementary steps of the dissociative mechanism. Variation of kinetically relevant steps (KRS) was selectively observed following hydrogenation activity modification from "C 2 H 3 *+H*" over Pd/Ce(OH)SO 4 ·xH 2 O to "C 2 H 4 *+H*" elementary step over Pd/CeO 2 in acetylene hydrogenation reaction. [Display omitted] • The reduction degree of the metal dominates the reactivity of C 2 H 2 hydrogenation. • This difference in activity can cause the switch of kinetically relevant steps. • Pd/Ce(OH)SO 4 ·xH 2 O catalyst enhances the C 2 H 4 selectivity. • Thermodynamic and kinetic aspects influencing C 2 H 4 selectivity are discussed. We report here that the reduction degree of the metal at the catalytic interface dominates the reactivity of acetylene hydrogenation, mainly in terms of turnover rates (TORs) and activation energies, which could certainly cause the switch of kinetically relevant steps (KRS) from "C 2 H 3 *+H*" over Ce(OH)SO 4 ·xH 2 O dispersed Pd catalyst to "C 2 H 4 *+H*" elementary step over Pd/CeO 2. Besides, a compact kinetic model has been established to describe the reaction process and the dissociative mechanism was confirmed by H 2 /D 2 exchange experiment. Meanwhile, the rate-determining step (RDS) and the main adsorbed species of the reaction were confirmed by systematic kinetic studies as well as in-situ FTIR analysis. More importantly, with the aid of parity fitting and gas isothermic adsorption analysis, the energetic relationship among the steps along with the acetylene hydrogenation is quantitatively described, which provides a good support and complement for the previous research, and helps researchers build up advanced reaction systems. [ABSTRACT FROM AUTHOR]

Photo‐thermal catalysis has been an attractive alternative strategy to promote chemical reactions for years, however, how light cooperates with thermal energy is still unclear. We meet this demand by exploring reaction mechanism via pressure dependency studies as well as H/D exchange experiments with HCOOH decomposition as a probe over a palladium nanoparticle (Pdn) and isolated Pd (Pd1) decorated LaCrO3/C3N4 composite catalyst, in which the H2 formation rate shows a first‐order dependence on HCOOH and inverse first‐order dependence on CO partial pressures no matter the reaction was driven by thermal or photo‐thermal energy. Additionally, negligible kinetic isotopic effects (KIEs: kH/kD) were determined under both dark and light conditions at 1.04 and 1.18 when the HCOOH was replaced by HCOOD. Besides, when the reactant HCOOH was further replaced by DCOOD, the KIE values of 1.55 (dark) and 1.92 (light) were obtained, which indicates that the HCOOH decomposition follows kinetically relevant (KR) of C−H bond rupture within HCOOH molecule under both thermal and photo‐thermal reaction conditions and the catalytic surface was found to be densely covered by CO based on the pressure dependency studies as well as the in situ Fourier transform infrared spectroscopy (FTIR) analysis. Clearly, the HCOOH decomposition driven by thermal and photo‐thermal energy follows the same reaction mechanism. Nevertheless, light induced hot electrons and the derived thermal effect do cause the enhancement of the reaction activity in some circumstances compared with bare thermal catalysis, which clarifies the confusion on cooperation mechanism of photo and thermal energies from the kinetic perspective. Hot electrons induced by photo‐illumination was confirmed by in situ FTIR CO chemisorption with ∼10 cm−1 redshift identified of the CO feature once light was introduced. Meanwhile, the photo thermal reaction system suffers from severe electron‐hole re‐combination at high reaction temperatures and make the thermal effect of photo irradiation dominant with respect to the effect at low reaction temperatures. This research provides insight to the mechanism on how photo‐thermal reaction works and draws attention to the photo‐thermal reaction process in boosting catalytic activity. [ABSTRACT FROM AUTHOR]

Keywords: HCOOH decomposition; photo-thermal reaction; reaction mechanism EN HCOOH decomposition photo-thermal reaction reaction mechanism 1 1 1 04/05/22 20220401 NES 220401 B Together photo- and thermal energy b promote catalytic reactions in a synergetic way. HCOOH decomposition, photo-thermal reaction, reaction mechanism Clear evidence of kinetically relevant consistency was found under both thermal and photothermal HCOOH decomposition reactions over a Pd/LaCrO SB 3 sb /C SB 3 sb N SB 4 sb composite. [Extracted from the article]

Photo‐thermal catalysis has been an attractive alternative strategy to promote chemical reactions for years, however, how light cooperates with thermal energy is still unclear. We meet this demand by exploring reaction mechanism via pressure dependency studies as well as H/D exchange experiments with HCOOH decomposition as a probe over a palladium nanoparticle (Pdn) and isolated Pd (Pd1) decorated LaCrO3/C3N4 composite catalyst, in which the H2 formation rate shows a first‐order dependence on HCOOH and inverse first‐order dependence on CO partial pressures no matter the reaction was driven by thermal or photo‐thermal energy. Additionally, negligible kinetic isotopic effects (KIEs: kH/kD) were determined under both dark and light conditions at 1.04 and 1.18 when the HCOOH was replaced by HCOOD. Besides, when the reactant HCOOH was further replaced by DCOOD, the KIE values of 1.55 (dark) and 1.92 (light) were obtained, which indicates that the HCOOH decomposition follows kinetically relevant (KR) of C−H bond rupture within HCOOH molecule under both thermal and photo‐thermal reaction conditions and the catalytic surface was found to be densely covered by CO based on the pressure dependency studies as well as the in situ Fourier transform infrared spectroscopy (FTIR) analysis. Clearly, the HCOOH decomposition driven by thermal and photo‐thermal energy follows the same reaction mechanism. Nevertheless, light induced hot electrons and the derived thermal effect do cause the enhancement of the reaction activity in some circumstances compared with bare thermal catalysis, which clarifies the confusion on cooperation mechanism of photo and thermal energies from the kinetic perspective. Hot electrons induced by photo‐illumination was confirmed by in situ FTIR CO chemisorption with ∼10 cm−1 redshift identified of the CO feature once light was introduced. Meanwhile, the photo thermal reaction system suffers from severe electron‐hole re‐combination at high reaction temperatures and make the thermal effect of photo irradiation dominant with respect to the effect at low reaction temperatures. This research provides insight to the mechanism on how photo‐thermal reaction works and draws attention to the photo‐thermal reaction process in boosting catalytic activity. [ABSTRACT FROM AUTHOR]