Penta-Twinned Rh@Pt Core-Shell nanobranches with engineered shell thickness for reversible and active hydrogen redox electrocatalysis.

Penta-twinned Rh@Pt core–shell nanobranches with synchronously engineered Pt-shell thickness and surface defects were created to serve as high-performance bifunctional hydrogen redox electrocatalysts. [Display omitted] • The PTw Rh@Pt x NBs have been facilely fabricated via a seed-mediated method. • The Pt-shell thickness can be precisely controlled in several atomic layers. • Surface twinned defects, compressive strain and the ligand effect are integrated. • The bifunctional Rh@Pt x NBs show excellent HER and HOR performance in an alkaline medium. Surface defects on electrocatalysts can effectively reduce reaction barriers and facilitate the kinetics of hydrogen evolution and oxidation reactions (HER/HOR). However, precisely engineering such surface structures remains a significant challenge. Herein, penta-twinned (PTw) Rh@Pt x core–shell nanobranches (NBs) with intense surface strains were facilely synthesized using PTw Rh NBs as the seeds for overgrowth of active Pt-shells. Through precisely regulating the supply of Pt precursor solution via a micro-syringe pump, the ultrathin Pt-shells conform to and replicate the twin defects of the PTw Rh seeds. Significantly, the shell thickness can be precisely controlled from 1.0, 2.0, and 3.8 to 5.0 atomic layers. Due to the integration of surface twinned defects, compressive strain and the core–shell ligand effect, these Rh@Pt x NBs exhibit superior hydrogen redox electrocatalytic performance compared to state-of-the-art Pt/C. Among the prepared materials, the Rh@Pt 0.83 NBs with a 3.8 atomic layer Pt-shell showed the highest mass activity (2.36 A mg Pt −1) and specific activity (6.55 mA cm−2) for HER at –0.07 V and presented the lowest overpotential (44 mV) at 10 mA cm−2, less than half the overpotential of the commercial Pt/C (98 mV). In terms of HOR, the Rh@Pt 0.83 NBs showed a superior exchange current density (1.97 mA cm−2), approximately 7 times higher than that of Pt/C. Our work provides a facile method to synchronously engineer the Pt-shell thickness and surface defects of Rh@Pt core–shell nanocatalysts for the creation of robust and bifunctional hydrogen redox electrocatalysts. [ABSTRACT FROM AUTHOR]