Local synergetic collaboration between Pd and local tetrahedral symmetric Ni oxide enables ultra-high-performance CO2 thermal methanation

Abstract

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 NiO_TPd-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 NiO_TPd-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 NiO_T reduction increases the number of metallic Ni sites. It further facilitates the H₂ splitting, therefore optimizing the CH₄ production yield of NiO_TPd-T. Most importantly, to the best of our knowledge, with such a unique Pd-to-NiO_T epitaxial structure, the NiO_TPd-T catalysts exhibit the highest CH₄ production yield among existing catalysts with the same loading and composition and of any geometric configuration.