In-situ transformation of Co(OH)_(2) into NH_(4)CoPO_(4)·H_(2)O on Co foil: 3D self-supported electrocatalyst with asymmetric local atomic and electronic structure for enhanced oxygen evolution reaction

Development of high efficient and stable water oxidation catalysts is essential for the realization of industrial water-splitting systems. Herein, a novel approach involving an in-situ transformation of Co(OH)2 nanosheets into NH4 CoPO4·H2 O nanoplates on Co foil is reported. As a 3 D self-supported oxygen revolution reaction(OER) electrocatalyst, the as-prepared NH4 CoPO4·H2 O/Co exhibits remarkable catalytic activity and exceptional stability. Specifically, it can deliver a current density of 10 m A cm^(-2) at a quite low overpotential of 254 m V with a small Tafel slope of 64.4 m V dec-1 in alkaline electrolyte. Through experimental study and theoretical analysis, the excellent OER performance can be attributed to enriched exposed active sites, favorable electron/proton transfer and mass transport, and its unique asymmetric local atomic and electronic structure. Thus, this present research not only provides a practicable in-situ transformation strategy to design 3 D self-supported electrocatalysts, but also enlightens a new way of developing transition-metal phosphates for efficient and stable water oxidation at atomic level.