Jin Yuan,Jinqiu Guo,Zhiwei He,Leisheng Che,Shanshan Chen,Hongbo Zhang
Graphical The photo-energy and thermal-energy in a synergetic way promote catalytic reaction together. In this article, the C−H bond rupture within HCOOH* was determined to be the rate-determining step with adsorbed CO* as the most abundant surface intermediates (MASIs) under both thermal and photo-thermal reaction conditions confirmed by kinetic isotopic effects and in situ FTIR characterizations. Clear evidence of kinetically relevant consistency was determined under both thermal and photo-thermal HCOOH decomposition reactions over Pd/LaCrO 3 /C 3 N 4 composite. 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 (Pd n ) and isolated Pd (Pd 1 ) decorated LaCrO 3 /C 3 N 4 composite catalyst, in which the H 2 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: k H / k D ) 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.
Zhe Bai,Zhenhua Wang,Tan Wang,Zeyu Wu,Ruilong Li,Xiaotian Gao,Yu Bai,Kening Sun
The partially filled d orbital of transition metal-based catalysts demonstrate excellent catalytic activity against polysulfides. However, an appropriate descriptor to reveal their structure-activity relationship is lacked. This study proposes a quantitative relationship between the e g occupancy of perovskite oxides and polysulfide catalytic activity, serving as an activity descriptor. LaCoO 3 , with a moderate e g occupation (t 2g 5 e g 1.08 ), demonstrates effective polysulfide anchoring and facilitated redox kinetics conversion compared to LaCrO 3 (t 2g 3 e g 0 ) and LaFeO 3 (t 2g 3 e g 2 ), showcasing exceptional catalytic performance. The degree of e g occupancy significantly influences the polysulfides adsorption strength, with empty or fully filled e g orbitals resulting in either strong or weak adsorption, respectively. LaCoO 3 -based batteries exhibit remarkable reversible capacity over 700 cycles at 1.0C, with a minimal capacity fading rate of 0.065 % per cycle. This work elucidates the crucial role of e g descriptor for evaluating the adsorption and conversion on polysulfides, offering insights into the development of innovative lithium-sulfur electrocatalysts.
The use of NO 2 sensors is a significant measure for reducing NO 2 emissions from industrial plants and vehicles. The performance of these devices considerably depends on the morphology of sensing electrodes, which in turn is directly influenced by the particle size of the raw powder used for gas detection. In this study, the particle size distribution (PSD) of LaCrO 3 powder was optimized through adjustments to calcination temperature, and the influence of such optimization on the morphology of sensing electrodes was considered in the examination of sensing performance. The results indicated that the sensor (S300) fabricated with the optimally calcined powder exhibited the best performance, achieving a high sensitivity of 52.52 mV/decade and a low limit of detection of 16.5 ppb—advantages stemming from the optimized gas diffusion pathways and triple phase boundaries (TPBs) in the sensing electrodes. The sensor also exhibits excellent selectivity, repeatability, and long-term stability. Overall, the PSD-oriented method developed in this research serves as an effective strategy for designing mixed-potential sensors, showing promising applications in high-temperature exhaust gas monitoring.
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