The large-scale decommissioning of lithium-ion batteries (LIBs) production is progressing rapidly, and the demand for environmentally friendly recycling and material recovery is rising. Collectively, this review has presented a series of studies on recent progress in using waste LIB black mass to synthesize various materials for water treatment, including synthesis methods, material structure and application performance of derived adsorbents, Fenton catalysts, persulfate-activating catalysts, etc. The above are based on rational material design and processing to create high-efficiency, multi-functional water treatment materials from black mass. Anode graphite-based adsorbents are a typical representative type with good heavy metal adsorption performance, and cathode-derived catalysts show fast degradation of organic pollutants via oxidative pathways. This review briefly introduces the shortcomings of the current state and provides some directions for further research to promote the construction of an effective pollution treatment model in the circular economy era.

Developing efficient electrocatalysts towards water oxidation is of critical importance for numerous environmental and energy technologies. Single-atom catalysts have been widely recognized as a promising route, they are however often anchored on semiconducting substrates such as hydroxides, which inherently limits the electrical conductivity and overall catalytic efficiency. In this work, single-atom Ru catalysts are immobilized on a semi-metallic layered double hydroxide substrate (Ru-SM LDH) to achieve highly efficient water oxidation. The as-designed Ru-SM LDH catalyst displayed an overpotential of 270 mV to deliver an oxygen evolution reaction (OER) current density of 100 mA cm⁻², which was 60 mV lower than that of commercial RuO₂. In-situ electrochemical impedance spectroscopy revealed that Ru-SM LDH exhibited a reduced solution resistance and diminished charge transfer resistance during catalysis, leading to the enhanced OER performance. An electrolyzer assembled with Ru-SM LDH anode and commercial Ni mesh cathode achieved a water electrolysis current density of 400 mA cm⁻² at 1.65 V and demonstrated exceptional stability for 1000 h, surpassing that of Ni||Ni electrolyzer (1.92 V, 350 h). These findings established the design of single-atom catalysts supported on semi-metallic hydroxide substrates as a robust pathway toward efficient water electrolysis catalysts.