Upcycling of spent LiFePO₄ cathodes to heterostructured electrocatalysts for stable direct seawater splitting

Abstract

The pursuit of carbon-neutral energy has intensified the interest in green hydrogen production from direct seawater electrolysis, given the scarcity of freshwater resources. While Ni-based catalysts are known for their robust activity in alkaline water oxidation, their catalytic sites are prone to rapid degradation in the chlorine-rich environments of seawater, leading to limited operation time. Herein, we report a Ni(OH)2 catalyst interfaced with laser-ablated LiFePO4 (Ni(OH)2/L-LFP), derived from spent Li-ion batteries (LIBs), as an effective and stable electrocatalyst for direct seawater oxidation. Our comprehensive analyses reveal that the PO43− species, formed around L-LFP, effectively repels Cl− ions during seawater oxidation, mitigating corrosion. Simultaneously, the interface between in situ generated NiOOH and Fe3(PO4)2 enhances OH− adsorption and electron transfer during the oxygen evolution reaction. This synergistic effect leads to a low overpotential of 237 mV to attain a current density of 10 mA cm−2 and remarkable durability, with only a 3.3 % activity loss after 600 h at 100 mA cm−2 in alkaline seawater. Our findings present a viable strategy for repurposing spent LIBs into high-performance catalysts for sustainable seawater electrolysis, contributing to the advancement of green hydrogen production technologies. Graphical abstract: [Figure not available: see fulltext.]