Application of coverage-dependent micro-kinetic study to investigate direct H 2 O 2 synthesis mechanism on Pd(111) surfa
- PDF / 1,375,963 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 86 Downloads / 132 Views
REGULAR ARTICLE
Application of coverage‑dependent micro‑kinetic study to investigate direct H2O2 synthesis mechanism on Pd(111) surface Keju Sun1 · Xin Song1 · Xianfeng Hao1 · Hai‑Yan Su2 · Yuanhui Xu1 Received: 31 May 2020 / Accepted: 5 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Hydrogen peroxide ( H2O2) is a highly effective, green oxidant that has been widely used in many chemical industries. Two coverage-dependent models are built in micro-kinetic study and successfully applied to investigate the direct H 2O2 synthesis mechanism from hydrogen and oxygen on Pd(111) surface. The computational results from both models show that the selectivity to H 2O2 can reach 99%, which takes advantage of the repulsion effects between the adsorbates and O* on the surface. H2O2 comes from the sequential hydrogenation of O2 and H2O as the by-product is dominantly from H2O2* decomposition. Therefore, how to inhibit H2O2* decomposition is the key step to achieve high selectivity on Pd(111) surface. Both models show H2O generation with higher apparent activation energy compared to H 2O2 formation, indicating that low temperature will benefit selectivity to H2O2. The calculated apparent activation energies are 22.30 kJ mol−1 for H2O2 formation and 48.67 kJ mol−1 for H 2O generation by the standard method, which agrees well with the experimental observations. It indicates that the coverage-dependent micro-kinetic study is a feasible method to investigate reaction mechanisms on various surfaces. Keywords Direct H2O2 synthesis · Pd catalyst · Coverage-dependent · Micro-kinetic study · DFT calculation
1 Introduction H2O2 is an ideal clean reagent used in chemical synthesis, or cleaning and bleaching, since the decomposition products are only water and oxygen [1]. Direct H 2O2 synthesis from molecular H2 and O2 has been proved to a green, atomically efficient and economical process, especially when operated on a small scale [2]. Pd-based catalysts are effective and active for direct H2O2 synthesis and have been extensively studied for more than a century [3]. The major goal of direct H2O2 synthesis is to prevent water formation, since the catalysts with high hydrogenation activity for O2 to H2O2, also are active for O2 to H2O, or degradation for H2O2. In * Keju Sun [email protected] 1
Hebei Key Laboratory of Applied Chemistry, Hebei Key Laboratory of Heavy Metal Deep‑remediation in Water and Resource Reuse, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China
School of Chemical Engineering and Energy Technology, Dongguan University of Technology, Dongguan 523808, China
2
addition, the formation of H2O is thermodynamically favorable compared to the synthesis of H 2O2, which makes it be a challenge to generate H2O2 in achieving high selectivity. In addition to many experimental studies on direct H2O2 synthesis [1–3], significant efforts in recent years have been made by theoretical researchers to understand th
Data Loading...
