Electrocatalytic hydrodechlorination on Pd composite electrode: Oxygen defect engineering of cobalt oxide as functional interlayer

Abstract

Palladium (Pd) modified nickel foam (NiF) serves as an effective composite electrode for electrocatalytic hydrodechlorination (ECH), but reducing the Pd dose while sustaining its activity remains challenging. This study proposes a Pd/CoO_x/NiF electrode, with an oxygen vacancy-enriched CoO_x interlayer introduced to disperse Pd and expose active sites. Compared to Pd/NiF, only 20 % of Pd is required to completely dechlorinate 2-chlorophenol (2-CP) within 2 h. By manipulating oxygen vacancies (OVs) with varied NaBH₄ reduction time, the Pd/CoO_x/NiF electrode shows 1.4-fold higher dechlorination efficiency of 2-CP at moderate OVs concentrations but suffers from a decline in activity at higher OVs concentrations. The electrode displays uniform nanosheet distribution, compact arrangement, and stability, maintaining 100 % 2-CP removal efficiency after five cycles. Quench studies showed that the H^⁎-mediated indirect reduction pathway contributed to 87.4 % of 2-CP removal, serving as the main dechlorination route for the Pd/CoO_x/NiF electrode. This study demonstrates that the Pd/CoO_x/NiF electrode with optimal oxygen vacancies achieves excellent ECH performance while significantly reducing Pd usage.