Surface‐Confined Ultra‐Low Scale Pd Engineered Layered Co(OH)2 toward High‐Performance Hydrazine Electrooxidation in Alkaline Saline Water

Applications of abundant seawater in electrochemical energy conversion are constrained due to the sluggish oxygen evolution reaction and the corrosive chlorine oxidation reaction. Hence, it is imperative to develop an efficient anodic reaction alternative suitable for coupling with the cathodic counterpart. Due to a low thermodynamic oxidation potential, hydrazine oxidation reaction (HzOR) offers a unique pathway to overcome these challenges. Herein, spontaneously in situ reduced atomic scale Pd surface-confined to electrochemically prepared layered Co(OH)₂ on carbon cloth is synthesized. This study reveals the hydrazine and Pd-dependent morphological evolution of Co(OH)₂ and its Pd hybrids into nanoparticulate form. Unlike various layered double hydroxides, Pd integrated Co(OH)₂ benefits from the contribution of Co(OH)₂ as an active HzOR catalyst and the reductive support to host Pd, resulting in synergistically improved performances. Mass activities of Pd in alkaline and alkaline saline electrolyte are 11.24 and 9.83 A mg_Pd ^-1 at 200 mV, respectively, corresponding to the highest HzOR activities among noble metals. The optimized Pd hybrid demonstrates ≈6.5 times the current density relative to PtC (14.91 mA cm^-2 at 200 mV) in alkaline saline water with hydrazine. These findings would be beneficial to realize high overpotential anodic alternatives and reduce over-dependence on freshwater for electrocatalysis.