Upcycling Spent Cathodes into Gradient Electrocatalysts for Seawater Electrolysis

The rapid growth of lithium-ion batteries (LIBs) is lighting a more sustainable transportation driven by electric vehicles. However, the end-of-life LIBs in the next decades will pose key challenges to the resource economy and environment due to lack of their high-value reuse. Here, we show a high-value, sustainable, and kilogram-scale upcycling strategy to convert spent LIBs cathode materials into NiCoMnFeP (NCMFP) electrocatalysts. These catalysts exhibit a gradient nanoparticle assembly architecture, enabling stable hydrogen production via direct seawater electrolysis. A facile surface reconstruction into active phosphate-terminated metal oxyhydroxide, efficiently hating chloride ions to enhance corrosion resistance, has been found by in-situ Raman investigation. The NCMFP therefore exhibits excellent durability identified by a small overpotential increase rate (OIR) of 1.27×10-4 V h-1 towards anodic oxygen evolution reaction (OER). Impressively, the NCMFP electrocatalyst operates stably (i.e. OIR=2.48 mV/°C) under complicated real-working conditions (0-400 mA cm-2 current density, 30-90°C temperature, 8-13 pH) for its long-term use in the direct seawater electrolysis process. Moreover, the NCMFP catalyst delivers ultralow overpotentials of 290-370 mV under the current densities of 50-300 mA cm-2, surpassing all the documented non-noble OER catalysts.