Nickel–Palladium Bimetallic Nanomaterials of Polyoxopalladates as Precursor Loaded on SBA15 for Enhanced Plasma-Assisted Ammonia Synthesis

Abstract

Bimetallic nanomaterials in conjunction with porous materials have emerged as the most promising catalytic materials for plasma-assisted ammonia synthesis. Adopting appropriate synthesis strategies to regulate the morphology of porous materials and the bimetallic active components is a potential way to further enhance their catalytic performance. However, the role of the morphology and composition of the materials remains unclear. In this study, we synthesize composite catalysts (MnPd₁₂/SBA15, CoPd₁₂/SBA15, CuPd₁₂/SBA15, and NiPd₁₂/SBA15) by regulating the morphology of the support mesoporous silica (SBA15) and using polyoxopalladates, which can precisely control molecular structure, as a precursor for bimetallic nanomaterials. Then, the performances of these catalysts for plasma-assisted ammonia synthesis are investigated. The results show that the NiPd₁₂/SBA15 composite catalyst has the highest ammonia synthesis yield, with a sample of 85 mg achieving an ammonia concentration up to 9070 ppm, and the energy consumption is as low as 77.75 MJ/mol. Additionally, it demonstrates good stability in cyclic experiments. The synergistic effect of SBA15 and NiPd₁₂ enables the NiPd₁₂/SBA15 catalyst to significantly enhance the yield of ammonia synthesis. It is due to the ability of NiPd₁₂ metals to stabilize the dissociation state of N₂, while having a relatively weak affinity for NH_x intermediates. This facilitates the desorption of NH₃ from the catalyst surface.