High-efficiency utilization of CO₂ facilitates the reduction of CO₂ concentration in the global atmosphere and hence the alleviation of the greenhouse effect. The catalytic hydrogenation of CO₂ to produce value-added chemicals exhibits attractive prospects by potentially building energy recycling loops. Particularly, methanol is one of the practically important objective products, and the catalytic hydrogenation of CO₂ to synthesize methanol has been extensively studied. In this review, we focus on some basic concepts on CO₂ activation, the recent research advances in the catalytic hydrogenation of CO₂ to methanol, the development of high-performance catalysts, and microscopic insight into the reaction mechanisms. Finally, some thinking on the present research and possible future trend is presented.

Identification of active site is critical for developing advanced heterogeneous catalysis. Here, a nickel/silica (Ni/SiO₂) catalyst was prepared through an ammonia-evaporation method for CO methanation. The as-obtained Ni/SiO₂ catalyst shows a CO conversion of 96.74% and a methane selectivity of 93.58% at 623 K with a weight hourly space velocity of 25,000 mL·g⁻¹·h⁻¹. After 150 h of continuous testing, the CO conversion still retains 96%, which indicates a high catalyst stability and long life. An in situ vacuum transmission infrared spectrum demonstrates that the main active sites locate at the interface between the metal Ni and the SiO₂ at a wave number at 2060 cm⁻¹ for the first time. The interesting discovery of the active site may offer a new insight for design and synthesis of methanation catalysts.

Exploring the interactions of oxygen with defective oxide is of importance to understand the microscopic process and performance of ZnO‐based oxygen sensors. The interactions of environmental oxygen with vacuum‐annealed defective ZnO have been studied by electrical methods, vacuum Fourier transform infrared spectroscopy, and in situ adsorption experiments. It was found that the vacuum‐annealed defective ZnO exhibits varied electrical response at different temperatures, which, by vacuum IR investigation, was ascribed to the subtle balance between formation of oxygen vacancies and their interactions with environmental oxygen. Further studies showed that two microscopic steps including surface adsorption and bulk diffusion were dominating the interactions between defective ZnO and environmental oxygen, and the corresponding apparent activation energies were estimated to be 0.093 and 0.67 eV through in situ adsorption experiments. The quite low activation barrier of oxygen adsorption on the defective ZnO was proposed to be responsible for the extreme high sensitivity of ZnO‐based oxygen sensors.

Copper-based catalysts are widely applied in catalytic CO conversion. Despite their importance in determining catalytic performance, the interaction of CO with different copper states has often been the subject of debate. Herein, we discuss the preparation of four different CuO_x states (namely, fully oxidized and reduced (O-573 and R-573, respectively) and 800 and 1000 K annealed (A-800 and A-1000, respectively)) through in situ treatments, comparing CO adsorption behaviors with vacuum-transmission IR spectroscopy. CO only weakly adsorbed on the A-1000 and R-573 surfaces, whereas it led to the creation of trace amounts of surface oxygen vacancies over the O-573 surface, providing adsorption sites for the subsequent CO. Meanwhile, the produced CO₂ re-adsorbed on the catalyst to form carbonate species. The reduction process was notably promoted over A-800 due to the presence of abundant surface oxygen vacancies, demonstrating the key role of Cu^δ+ in oxygen vacancies, rather than merely its chemical state, in dominating the interaction of CO with CuO_x.

We present a novel ultrahigh vacuum (UHV) compatible polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) system that is designed for in situ surface spectroscopic characterization on a transferable single crystalline sample. The innovative design of manipulator rod and high-pressure cell (HPC) ensures free movement of the sample between the preparation chamber and the HPC, and perfect separation of them during high pressure experiments. The pressure in the HPC can be varied from UHV (10 ⁻⁹ mbar) to ambient pressure (1000 mbar) while keeping the preparation chamber under UHV conditions. The design of the transferable sample holder and receiving stage allows precise temperature measurement and allows convenient sample changing. In situ IRRAS measurements under variable pressure and temperature can be conducted either in the conventional mode or with polarization modulation. Other surface characterization methods can also use the preparation chamber; thus, the system is endowed with the capability for systematic investigations of surface catalytic reactions. A case study of CO adsorption and oxidation on Pt(111) demonstrates the performance of the system.