Graphene-armored nickel nanoparticles promote stable and selective butadiene hydrogenation

Abstract

A facile pyrolysis strategy utilizing citric acid was employed to fabricate nickel nanoparticles encapsulated by graphene layers (Ni@C) for selective butadiene hydrogenation. Systematic adjustment of calcination temperatures (873–1173 K) enabled control over Ni particle size (12.8–27.5 nm) and carbon encapsulation thickness. Catalysts synthesized at higher temperatures (1073–1173 K) demonstrated much superior performance, achieving 97 % butene selectivity and retaining >98 % initial activity over 100 h at 373 K. In contrast, catalysts carbonized at lower temperatures (873–973 K) displayed rapid deactivation linked to excessive carbon deposition. Kinetic insights indicated that enlarged Ni particles strengthened butadiene adsorption while the relative adsorption strength between butadiene and intermediate product – butenes were increased, thereby suppressing over-hydrogenation to butane. The graphene overlayers not only effectively mitigated Ni oxidation when exposed to air, but also prevent metal agglomeration under hydrogenation conditions, ensuring structural integrity. Comparative evaluations underscored the superiority of well-designed graphene-capped Ni catalysts over traditional systems in balancing selectivity and longevity. This study advances the rational design of encapsulation-engineered catalysts for industrial hydrogenation processes requiring precise product control.