Waste is the best: end-of-life lithium ion battery-derived ultra-active Ni3+-enriched β-Ni(OH)2 for the electrocatalytic oxygen evolution reaction

Abstract

Urban mining of e-waste, especially end-of-life lithium ion batteries (LIBs), is gaining momentum as a potential secondary source for valuable metals and due to the environmental impact associated with their disposal. Utilization of these metals in renewable energy-related applications could cater to the realization of a circular economy by reusing industrial waste for sustainable applications. In this regard, we explore the formation of Ni³⁺-enriched β-Ni(OH)₂ from spent LIBs and analyze its efficacy as an electrocatalyst for the oxygen evolution reaction (OER). As-synthesized β-Ni(OH)₂ requires a minimal overpotential of 300 mV to reach a current density of 50 mA cm⁻² with a low Tafel slope of 42.7 mV dec⁻¹. The usual sluggish kinetics of the OER is mitigated due to the strategic presence of a small amount of NiOOH, and surface oxygen vacancies. In situ impedance analysis strongly supports the improved OER performance of Ni³⁺-rich β-Ni(OH)₂ due to facile OH* adsorption followed by rapid charge transfer at the electrode–electrolyte interface. The combined effect is manifested in ultrafast OER with mass activity 1044 mA mg⁻¹ and TOF 257.2 s⁻¹, which are exceptional for Ni-containing systems. The structural integrity of the catalyst was validated with post-OER characterization experiments, delineating the applicability of e-waste-derived materials for renewable energy applications.