CaH2-promoted activity of Ni-carbonate interface for CO2 methanation

• Published in: Journal of energy chemistry 2025-01, Vol.100, p.522-532
• Main Authors: Wang, Jin-Peng, Mao, Guo-Cui, Jiang, Hui-Lin, Dong, Bao-Xia, Teng, Yun-Lei
• Format: Article
• Language: English
• Subjects: Carbonate; CO2 methanation; Metal hydride; Metal-carbonate interface; Ni catalysts
• ISSN: 2095-4956
• DOI: 10.1016/j.jechem.2024.09.005

It was found that CaH2 can promote activity of Ni-carbonate interface for CO2 methanation by modifying the electronic structure of Ni and tuning the structural properties of CaCO3. [Display omitted] Transition metal-carbonate interfaces often act as active sites in heterogeneous catalytic reactions. The interface between transition metal and metal carbonate exhibits a dynamic equilibrium during the CO2 hydrogenation reaction, involving surface carbonate hydrogenation and CO2 chemisorption. Nonetheless, there have been few reports on engineering the activity of the interface between transition metal and alkaline earth metal carbonate for catalytic CO2 conversion. This work demonstrated that the incorporation of CaH2 in Ni/CaCO3 enhances the CO2 methanation activity of the catalysts. The CO2 conversion for Ni/CaH2-CaCO3 reached 68.5% at 400 °C, which was much higher than that of the Ni/CaCO3 (31.6%) and Ni/CaH2-CaO (42.4%) catalysts. Furthermore, the Ni/CaH2-CaCO3 catalysts remained stable during the stability test for 24 h at 400 °C and 8 bar. Our research revealed that CaH2 played a crucial role in promoting the activity of the Ni-carbonate interface for CO2 methanation. CaH2 could modify the electronic structure of Ni and tune the structural properties of CaCO3 to generate medium basic sites (OH groups), which are favorable for the activation of H2 and CO2. In-situ Fourier transform infrared spectroscopy (FTIR) analysis combined with density functional theory calculations demonstrated that CO2 activation occurs at the hydroxyl group (OH) on the CaH2-modified Ni-carbonate surface, leading to the formation of CO3H* species. Furthermore, our study has confirmed that CO2 methanation over the Ni/CaH2-CaCO3 catalysts proceeds via the formate pathway.