90. Controllable co-generation of bulk and surface hydrogen species in a palladium membrane reactor via collaborative electrolysis

Kejian Kong, Xingjian Xu, Xiang Liu, An-Zhen Li, Mingfei Shao and Haohong Duan*
Chem Catal. 2025, 101602
DOI: 10.1016/j.checat.2025.101602

Summary
Electrochemical reduction over palladium catalysts, in which Pd hydride with bulk hydrogen (H_bulk) is considered the authentic catalytic phase, is widely reported. However, its catalytic mechanism and relation with directly generated surface hydrogen (H_surface) remain elusive. Herein, with a Pd membrane reactor as an operation platform, H_bulk and H_surface can be controllably co-generated in one system. By simultaneously applying a polarization current at the electrochemical and chemical compartments, transmembrane electrolysis (TME) generates H_TME (representing H_bulk), and direct electrolysis (DE) delivers H_DE (serving as H_surface). Using this system, we demonstrate kinetic orthogonality between the two species and suppressed recombination to form H₂, highlighting the chemical difference between H_bulk and H_surface. Taking advantage of their kinetic orthogonality, we implement a collaborative electrolysis (CE) system that outperforms a traditional Pd membrane reactor at the same total current density in the electrochemical hydrogenation of various substrates.