At the critical stage of achieving the "dual carbon" target, how to turn the "greenhouse gas" CO ₂ into high-value methanol has always been a hot topic in the scientific research community. Recently, good news came from the research team of Zhejiang University and Inner Mongolia Daqingshan Laboratory - their developed Cu ZnO/Nb ₂ C @ Nb ₂ O ₅ catalyst has shown amazing performance in the CO ₂ hydrogenation to methanol reaction, with a methanol yield of up to 247mg/(gcat · h) and selectivity of 74.3%. The performance has almost no degradation after 60 hours of continuous operation! This achievement provides a new solution for carbon resource recycling, and the related research ideas deserve special attention.

When it comes to CO ₂ hydrogenation to methanol, the first thing that comes to mind is the traditional Cu/ZnO/Al ₂ O3 catalyst. Although this type of catalyst has been preliminarily applied, there have always been two fatal problems: first, Cu particles are prone to agglomeration and ZnO is prone to sintering at high temperatures, resulting in a short service life; The second issue is that methanol selectivity has never improved, making it difficult to meet the high requirements of industry.

Team researcher: "As a promoter in traditional catalysts, Al ₂ O ∝ has limited anchoring ability for Cu and ZnO, and the metal support interaction (SMSI) can easily over encapsulate active sites, which in turn affects catalytic efficiency. ”In order to overcome this limitation, the team turned their attention to the popular new material in recent years - MXene.

MXene is a type of two-dimensional transition metal carbide/nitride with the general formula M ₙ₊₁ X ₙ T ₓ. The "M site" (unsaturated transition metal site) combines the high diffusivity of carbon materials with the reducibility of metal oxides, which can regulate the structure of the loaded metal and enhance the adsorption of small molecule gases. The Nb ₂ C MXene selected by the team this time has become the "core skeleton" of the catalyst due to its unique interlayer structure and unsaturated Nb sites.

The key breakthrough in the research lies in the team's clever utilization of the "electron metal carrier interaction (EMSI)" between Nb ₂ C and Cu. Through X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations, it has been confirmed that the unsaturated Nb sites in Nb ₂ C will transfer electrons to Cu species, causing the Cu surface to become a "electron rich state" - which is precisely the "key code" for CO ₂ activation!

The electron rich Cu surface can more easily 'grab' CO ₂ molecules, while the Nb site can also promote the adsorption and dissociation of H ₂. ”Through hydrogen temperature programmed reduction (H ₂ - TPR) and temperature programmed desorption (TPD) experiments, it was found that Nb ₂ C @ Nb ₂ O ₅ (formed by partial oxidation of Nb ₂ C) not only retains strong adsorption capacity for H ₂ and CO ₂, but also effectively inhibits CO desorption through strong adsorption of CO *, guiding the reaction towards the direction of methanol generation.

It is worth mentioning that the team found the optimal ratio of 4:2:10 by regulating the ratio of Cu: Zn: Nb ₂ C. At this point, the catalyst forms a stable Cu Zn Nb interface structure, which ensures the dispersion of Cu nanoparticles and enhances the EMSI effect, achieving a balance between "activity" and "selectivity".

In order to understand how CO ₂ is gradually converted into methanol, the team utilizedEnergy Spectrum TechnologyiCAN 5000Research grade Fourier Transform Infrared SpectrometerWe conducted high-pressure in-situ DRIFTS experiments. Under real reaction conditions of 3MPa and 120-240 ℃, the "dynamic trajectory" of key intermediates was successfully captured:

At 120 ℃, HOCO * (1652cm ⁻¹, 1540cm ⁻¹) and CO * (2077cm ⁻¹, 2057cm ⁻¹) signals were detected, indicating that CO ₂ was first converted to HOCO * and then dissociated into CO *;

At 200 ℃, the signal of H3CO * (981cm ⁻¹, 1051cm ⁻¹) increased, indicating that CO * began to convert to methanol precursor;

•240℃ 时，H₃COSignal, while no HCOO detectedThe characteristic peak of formate directly confirms that the reaction follows the "RWGS (reverse water gas shift)+CO hydrogenation" pathway, rather than the traditional formate pathway.

This discovery provides a clear direction for subsequent catalyst design, based on previous understanding of the reaction pathways of some Cu based catalysts. ”

Performance surpasses similar catalysts, industrial application is just around the corner

Under the reaction conditions of 240 ℃ and 3MPa, the performance of this Cu ZnO/Nb ₂ C @ Nb ₂ O ₅ catalyst can be described as:

The methanol yield is 247mg/(gcat · h), far exceeding most reported Cu based catalysts;

Methanol selectivity is 74.3%, effectively inhibiting the generation of by-product CO;

Continuous operation for 60 hours, with almost no fluctuations in CO ₂ conversion rate, methanol selectivity, and yield, and full structural stability.

Compared to traditional Cu/ZnO/Al ₂ O3 catalysts, this new catalyst not only solves the pain points of "short lifespan and low selectivity", but also leaves a huge space for subsequent performance optimization with the controllability of MXene materials. Our next step is to further strengthen the electronic interaction between Nb sites and Cu, explore reaction performance at higher pressures and temperatures, and promote its industrial application. ”

(This article is based on the relevant research results of the Zhejiang University team. The core data and mechanism analysis of the original text have been rigorously validated through experiments. If you need to further understand, you can refer to the original text or contact the team for supporting information.)

The Fourier transform infrared spectrometer mentioned in this study is the iCAN5000 research grade Fourier transform infrared spectrometer produced by Tianjin Energy Spectrum Technology

• Interferometer: Equipped with three-dimensional laser control automatic adjustment and high-speed scanning dynamic collimation control functions, the maglev interferometer technology ensures high stability and accuracy for long-term detection, without spectral deviation and distortion. Good reliability, stability, and anti-interference performance;

• Optical system: All use gold reflectors and adopt a dry and sealed all alloy optical table box. The optical path leads out and leads in the person equipped with anti fogging coating infrared transmission sealing window panels, which have high stability and dry and moisture-proof performance. The optical stage and sample chamber adopt an independent separate design, and the oversized sample chamber can expand various infrared analysis and detection applications.

• Detector: Optional high-sensitivity DLATGS, electronic refrigeration MCT, liquid nitrogen refrigeration MCT, etc.

• Solid state laser: stable performance, with a service life of over 10 years

• Light source: Imported high-performance, long-life light source with automatic sleep function.