Crafting a Methanation-Resistant, Reverse Water–Gas Shift-Active Nickel Catalyst with Significant Nanoparticle Dimensions Using the Molten Salt Approach

• Published in: ACS sustainable chemistry & engineering 2024-10, Vol.12 (40), p.14771-14783
• Main Authors: Lin, Yu-Chuan, Rajagopal, Sanjeevan, Chou, Pei-Tung, Peng, Po-Yang, Lu, Ying-Rui, Chen, Chi-Liang, Tsai, Meng-Hsuan, Wang, Chia-Hsin
• Format: Article
• Language: English
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.4c05125

Silica-supported Ni-based catalysts, synthesized using the molten salt method (MSM) in a NaCl and KCl medium, were employed in a reverse water–gas shift (RWGS) system. These catalysts featured Ni0 particles (10–40 nm) coated with salts, which showed inhomogeneous distribution, with Na and K surface enrichments and Cl depletion. This resulted in Ni-salt interface interactions. The most promising catalyst, Ni3@Na6.5K8.7(10.7)/SiO2-red, achieved near-theoretical CO2 conversions at 450 °C (44%) and 500 °C (49%), producing CO exclusively within 350–500 °C. It demonstrated durability and coking resistance over a 100 h test. In situ analyses indicated that RWGS proceeded via a redox mechanism. In addition to the bicarbonate (*HCO3) and linear-bound CO (*CO) pathways, Ni3@Na6.5K8.7(10.7)/SiO2-red revealed a new route involving monodentate carbonate (m-*CO3) as an intermediate. Residual salts were found to suppress the deep hydrogenation of formate (*HCO2) and formyl (*CHO) to CH4. These findings underscore the potential of MSM-synthesized Ni-based catalysts for efficient reduction of CO2 to CO.