Local synergetic collaboration between Pd and local tetrahedral symmetric Ni oxide enables ultra-high-performance CO₂thermal methanation

A hierarchically structured bimetallic nanocatalyst (NC) comprising a metallic Pd-nanocluster adjacent to local tetrahedral symmetric Ni-oxide and a thin layer of tetramethyl orthosilicate (TMOS) decoration (denoted as NiOTPd-T) is synthesized by sequential control of the metal ion adsorption followed by wet chemical reduction on a carbon nanotube support. By cross-referencing the results of the physical structure inspections, in situ ambient pressure X-ray photoelectron spectroscopy, and gas chromatography-mass spectrometer analysis, we demonstrate that the NiOTPd-T gains an optimum production yield of 1905.1 mmol g-1 of CH4 which is more than 10-fold improved as compared to that of TMOS decorated Pd nanocatalysts (Pd-T) at 573 K. Such an exceptional performance is attributed to the local synergetic collaboration between CO chemisorption on Pd atoms and H2 splitting on both the Pd and Ni atoms at the interface region. Once the collaboration is triggered, the subsequent NiOT reduction increases the number of metallic Ni sites. It further facilitates the H2 splitting, therefore optimizing the CH4 production yield of NiOTPd-T. Most importantly, to the best of our knowledge, with such a unique Pd-to-NiOT epitaxial structure, the NiOTPd-T catalysts exhibit the highest CH4 production yield among existing catalysts with the same loading and composition and of any geometric configuration.