Crafting a\nMethanation-Resistant, Reverse Water–Gas\nShift-Active Nickel Catalyst with Significant Nanoparticle Dimensions\nUsing the Molten Salt Approach

Silica-supported Ni-based catalysts, synthesized using\nthe molten\nsalt method (MSM) in a NaCl and KCl medium, were employed in a reverse\nwater–gas shift (RWGS) system. These catalysts featured Ni<sup>0</sup> particles (10–40 nm) coated with salts, which showed\ninhomogeneous distribution, with Na and K surface enrichments and\nCl depletion. This resulted in Ni-salt interface interactions. The\nmost promising catalyst, Ni<sub>3</sub>@Na<sub>6.5</sub>K<sub>8.7</sub>(10.7)/SiO<sub>2</sub>-red, achieved near-theoretical CO<sub>2</sub> conversions at 450 °C (44%) and 500 °C (49%), producing\nCO exclusively within 350–500 °C. It demonstrated durability\nand coking resistance over a 100 h test. In situ analyses indicated\nthat RWGS proceeded via a redox mechanism. In addition to the bicarbonate\n(*HCO<sub>3</sub>) and linear-bound CO (*CO) pathways, Ni<sub>3</sub>@Na<sub>6.5</sub>K<sub>8.7</sub>(10.7)/SiO<sub>2</sub>-red revealed\na new route involving monodentate carbonate (m-*CO<sub>3</sub>) as\nan intermediate. Residual salts were found to suppress the deep hydrogenation\nof formate (*HCO<sub>2</sub>) and formyl (*CHO) to CH<sub>4</sub>.\nThese findings underscore the potential of MSM-synthesized Ni-based\ncatalysts for efficient reduction of CO<sub>2</sub> to CO.