Regulating the Electronic Structure of Pd Nanoparticles on NH₃‐Pretreated Nano‐Flake TiO₂ for Efficient Hydrogenation of Nitrile Butadiene Rubber

Abstract The heterogeneous selective hydrogenation of nitrile butadiene rubber (NBR) is an efficient method to generate high value‐added hydrogenated NBR. Nevertheless, the inherent large molecular size and high spatial hindrance of polymers lead to poor activity and metal loss. Herein, we report a simple support ammonia pretreatment strategy for the synthesis of efficient N‐doped Pd catalyst and applied for the NBR hydrogenation. The results reveal that N doping enhances electron transfer from the support to Pd more effectively than oxygen‐rich vacancy support, thereby substantially enhancing the electron cloud density and stability of the Pd sites. The formation of more electron‐rich Pd sites not only significantly enhances the adsorption‐activation ability of C=C and H 2 , but also lowers the apparent activation energy of the reaction. As a result, the Pd/N‐TiO 2 ‐R demonstrates best activity with a hydrogenation degree (HD) of 98 % and a TOF value of 335 h −1 , significantly higher than that of Pd/TiO 2 −R (HD=83 %, 282 h −1 ) and Pd/TiO 2 (HD=74 %, 204 h −1 ). This strategy will provide new inspiration to improve the activity and stability of Pd/TiO 2 catalysts for the hydrogenation of unsaturated polymers.