Cryptomelane nanorods coated with Ni ion doped Birnessite polymorphs as bifunctional efficient catalyst for the oxygen evolution reaction and degradation of organic contaminants

Abstract

The intelligent design or development of dual-functional catalysts using nonprecious metals especially for the oxygen evolution reaction (OER) in sustainable energy systems and degradation of organic pollutants is still a difficult and a significant challenge. Furthermore, the development of these catalysts is of great importance in terms of energy security and solution of the environmental problems. To meet these requirements, herein, we describe the synthesis of a Ni-ion doped Birnessite@Cryptomelane (Ni2+/B@Cr) hybrid structure as a bifunctional efficient catalyst for the OER in neutral media and degradation of dye pollutants. The Ni2+/B@Cr catalyst exhibited a sharp onset potential at 390 mV (vs. RHE) and achieved a current density of 1 mA cm(-2) at a low q of 430 mV with a Tafel slope of similar to 96 mV dec(-1). The results of electrochemical impedance spectroscopy (EIS) studies indicated that Ni intercalation into birnessite layer and heterostructure of the hybrid electrocatalyst Ni2+/B@Cr increased the conductivity by lowering the resistance of charge transfer (R-ct = 4.82 Omega) and oxygen evolution processes (R-OER = 4.13 Omega). The durability assay identified Ni2+/B@Cr as stable electrocatalyst with 10% loss of activity after long-term stability tests (10 h, under 500-mV overpotential). In addition, the Ni2+/B@Cr achieved high (86.67 s(-1) g(-1)) and rapid (173 s) catalytic performance for the reduction of methylene blue (MB). Overall, this paper presents a low-cost production strategy for the design of highly efficient bifunctional catalysts, offering boosted electrocatalytic and degradation performance for water oxidation and organic dye contamination, respectively.