Electrocatalytic CO2 conversion on boron nitride nanotubes by metal single-atom engineering

Atomically dispersed single metal on defective boron nitride nanotubes (BNNTs) show promising potential for CO2 electrocatalytic reduction reaction (CO2ERR). Using density functional theory calculations, we explore the CO2ERR mechanism on single-atom catalysts (SACs) supported on BNNTs as well as assess their electrocatalytic performance of these catalysts. Boron or nitrogen vacancies in BNNTs are doped with palladium, platinum, or rhodium atoms to form three-coordinated metal centers, denoted as M@BNNT-V (M = Pt, Rh, Pd; V = B vacancy or N vacancy). Pt@BNNT with boron vacancies (Pt@BNNT-Bvac) demonstrates a tendency to facilitate multielectron reduction processes leading to the formation of complex molecules such as CH2O, CH3OH, and CH4 with a limiting potential (UL) of -0.36 V. Conversely, Rh@BNNT-Bvac and Pd@BNWNT-Bvac show significantly lower limiting potentials of -0.06 V and -0.12 V, respectively, for the reduction to formic acid (HCOOH), with Rh@BNNT-Bvac exhibiting enhanced activity and selectivity. Additionally, the deep reduction to other hydrocarbons or oxygenates, which typically requires potentials of -0.72 V and -0.60 V, appears less likely on both Rh and Pd doped BNNT-Bvac, further delineating the nuanced performance differences induced by metal type and coordination environment within the BNNT structure.