External electric field-assisted electronic restructuring of transition metal oxides derived from spent lithium-ion batteries to enhance persulfate activation

[Display omitted] •External electric field polarization promotes the gathering of Co and Ni.•XPS proves that external electric field polarization reconstructs the electronic structure of NCM.•Polarized catalyst E-PD@NCM allows > 45 % increase in SMX degradation rate.•Non-free radical processes were mainly responsible for the degradation of SMX. Discarded lithium-ion batteries contain abundant transition metal oxides, which benefit to persulfate activation. Inspired by electrocatalysis and the structural properties of the ternary lithium-ion battery cathode, we investigate the effect of external electric field polarization on the electronic structure reorganization behavior of NCM and the catalytic performance of peroxymonosulfate (PMS). Firstly, external electric field polarization promotes the gathering of Co and Ni. Secondly, the electric field modified waste NCM (E-PD@NCM) has 1.61 times higher degradation rate of SMX than the non-electric field modified waste NCM (PD@NCM). Meanwhile, electric field polarization increased the oxygen vacancy content in the spent NCM, and the abundant oxygen vacancies effectively restructured the electronic structure of E-PDNCM, further accelerating charge transfer and significantly improving the PMS activation efficiency. The catalytic mechanism analysis indicates that SO4•− and 1O2 play a dominant role in the degradation of pollutants. This study demonstrates the high catalytic performance of TMO through reorganization of the electronic structure and provides a new strategy to guide the design of other metal oxide nano-catalysts.