Synergistic effects of crystal-facet on dehalogenation kinetics and poison tolerance of Pd-based electrocatalytic membranes for efficient removal of halogenated pollutants

Halogenated pollutants (HPs) in water pose serious risks, yet conventional dehalogenation technologies often suffer from sluggish kinetics and rapid catalyst deactivation. Here, we unveil the synergistic effects of crystal-facet on dehalogenation kinetics and poison tolerance of Pd-based electrocatalytic membranes (EMs) for ultrafast and robust dehalogenation. Preferential exposure of the (111) facet drives the electrodeposited Pd layer to evolve from a loose to a dense porous architecture due to its lower surface energy. This topological transition reduces the average pore size by ∼46% and enhances the volumetric density of active sites. Concurrently, it facilitates pollutant diffusion and improves atomic hydrogen (*H) utilization, compensating for the lower *H generation capacity of (111) facet. Furthermore, we identify phenol desorption, rather than halogen desorption, as the rate-determining step and reveal a linear correlation between the energy barrier and the d-band center of Pd facets. The (111) facet, possessing a d-band center 0.10 and 0.18 eV lower than those of the (200) and (220) facets, respectively, significantly facilitates phenol desorption and thereby promotes active site renewal. Benefiting from these synergistic effects, the (111)-dominated Pd layer delivers 5–8 times faster kinetics and higher durability than (200)-dominated counterparts, eliminating >99% of 4-chlorophenol within ∼8 ms. Moreover, the (111)-dominated EM enables nearly complete and durable removal of trace 4-chlorophenol from real drinking water with a low energy consumption of 0.09 kWh/m³, outperforming conventional membrane separation and electrochemical technologies. Overall, this study offers novel mechanistic insights into the fundamental role of crystal-facet in dictating dehalogenation kinetics and poison tolerance of EMs, paving the way toward rational design of high-performance EMs for advanced water purification.