Kuwahara Yasutaka, Mihogi Takashi, Hamahara Koji, Kusu Kazuki, Kobayashi Hisayoshi, Yamashita Hiromi
Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan
Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University 2-1 Yamada-oka Suita Osaka 565-0871 Japan.
Chem Sci. 2021 Jun 28;12(29):9902-9915. doi: 10.1039/d1sc02550c. eCollection 2021 Jul 28.
Production of methanol from anthropogenic carbon dioxide (CO) is a promising chemical process that can alleviate both the environmental burden and the dependence on fossil fuels. In catalytic CO hydrogenation to methanol, reduction of CO to intermediate species is generally considered to be a crucial step. It is of great significance to design and develop advanced heterogeneous catalysts and to engineer the surface structures to promote CO-to-methanol conversion. We herein report an oxygen-defective molybdenum sub-oxide coupled with Pt nanoparticles (Pt/H MoO ) which affords high methanol yield with a methanol formation rate of 1.53 mmol g h in liquid-phase CO hydrogenation under relatively mild reaction conditions (total 4.0 MPa, 200 °C), outperforming other oxide-supported Pt catalysts in terms of both the yield and selectivity for methanol. Experiments and comprehensive analyses including X-ray absorption fine structure (XAFS), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and density functional theory (DFT) calculations reveal that both abundant surface oxygen vacancies (V) and the redox ability of Mo species in quasi-stable H MoO confer the catalyst with enhanced adsorption and activation capability to subsequently transform CO to methanol. Moreover, the Pt NPs act as H dissociation sites to regenerate oxygen vacancies and as hydrogenation sites for the CO intermediate to finally afford methanol. Based on the experimental and computational studies, an oxygen-vacancy-mediated "reverse Mars-van Krevelen (M-vK)" mechanism is proposed. This study affords a new strategy for the design and development of an efficient heterogeneous catalyst for CO conversion.
由人为产生的二氧化碳（CO₂）制取甲醇是一个很有前景的化学过程，它既能减轻环境负担，又能减少对化石燃料的依赖。在催化CO₂加氢制甲醇过程中，将CO₂还原为中间物种通常被认为是关键步骤。设计和开发先进的多相催化剂并调控其表面结构以促进CO₂向甲醇的转化具有重要意义。我们在此报道了一种氧缺陷型氧化钼与铂纳米颗粒耦合的催化剂（Pt/H₂MoO₃），在相对温和的反应条件下（总压4.0 MPa，200℃）进行的液相CO₂加氢反应中，该催化剂具有高甲醇产率，甲醇生成速率为1.53 mmol g⁻¹ h⁻¹，在甲醇产率和选择性方面均优于其他氧化物负载的铂催化剂。包括X射线吸收精细结构（XAFS）、漫反射红外傅里叶变换（DRIFT）光谱和密度泛函理论（DFT）计算在内的实验和综合分析表明，准稳态H₂MoO₃中丰富的表面氧空位（V）和Mo物种的氧化还原能力赋予了催化剂增强的吸附和活化能力，从而随后将CO₂转化为甲醇。此外，Pt纳米颗粒充当H解离位点以再生氧空位，并作为CO₂中间体的加氢位点，最终生成甲醇。基于实验和计算研究，提出了一种氧空位介导的“逆Mars-van Krevelen（M-vK）”机制。这项研究为设计和开发用于CO₂转化的高效多相催化剂提供了新策略。
