Metal–support interface engineering of Ni catalysts for improved H2 storage performance: Grafting alkyltriethoxysilane onto commercial alumina

Abstract

Tuning metal–support interface in supported Ni catalysts is a promising approach for overcoming the agglomeration of Ni particles and the low reducibility of Ni species. This study describes a facile two-step method to produce active Ni catalysts for the hydrogenation of benzyltoluene. In the first step, alkyltriethoxysilanes (CnTES, n = 1, 3, and 8) were grafted onto the surface of commercial Al2O3. The maximum Si/Al ratio of the prepared CnTES-on-Al2O3 materials was determined to be approximately 2.9 mol.%, which can vary depending on the surface properties of Al2O3. The second step was H2 reduction of the Ni precursor loaded on the CnTES-on-Al2O3 materials to remove alkyl substituents from the grafted CnTES and form Ni particles on the surface of silica grafted onto alumina (SGA). The hydrogenation performance of the obtained Ni/SGA_CnTES catalysts was improved with increasing Si/Al ratio owing to higher Ni dispersion and more abundant metallic Ni. The activity of the Ni/SGA_2.9CnTES (Si/Al = 2.9 mol.%) catalysts exhibited a volcano-shaped relationship with the length of the alkyl substituent of grafted CnTES, reaching the maximum for C3TES. Notably, Ni/SGA_2.9C3TES showed excellent ability for the adsorption of H2 and substrate, as well as high stability, resulting from the reduced agglomeration of Ni particles and the modulated metal–support interface. Therefore, the demonstrated synthesis approach can render Ni catalysts servable to promote the commercialization of liquid organic hydrogen carrier system.