Interstitial Modification of Palladium Nanocubes with Nitrogen Atoms Promotes Aqueous Electrocatalytic Alkyne Semihydrogenation

Abstract

Developing nanostructures to drive the selective and durable electrocatalytic semihydrogenation of alkynes to alkenes with a high Faradaic efficiency (FE) is highly desirable. Here, we propose that the desired catalytic materials should meet three requirements: (1) catalyst oxidation potential higher than alkyne reduction potential, (2) easy desorption of alkene and difficult formation of PdH x, and (3) higher energy barriers for H* self-coupling than H* adds to an alkyne molecule. Thus, Pd 2 N nanocubes with nitrogen-atom-modified Pd interstitial sites are designed and synthesized to achieve 95.7% alkyne conversion, 97.8% alkene selectivity, and 72.4% alkene FE. The catalyst can be used for 18-cycle measurements without performance decline. A mechanistic study shows that the high selectivity is due to the inhibited PdH x, the weakened alkene adsorption, and the increased energy barrier for alkene hydrogenation. The high energy barrier for H* coupling to release H 2 leads to the high alkene FE. In addition, the potential-independent alkene selectivity enables Pd 2 N to fit the fluctuating voltage in a solar-powered system. Furthermore, Pd 2 N is suitable for other functionalized alkynes and deuterated alkyne semihydrogenation.