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 18cycle 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.