The space-charge region at NiFe-MOF?LDH p-n junction by self-sacrificing LDH to boost oxygen evolution tandem with in-situ electro-Fenton

The rational design of p-n heterojunction was highly desirable to optimize charge distribution at space-charge region, tailoring the adsorption free energy of intermediate matters, and to boost the oxygen evolution reaction (OER) and in situ electro-Fenton (EF) reaction. Herein, a self-sacrificing strategy has been employed to construct the NiFe-MOF subset of LDH nanosheet arrays on carbon cloth (CC), directly using NiFe-LDH as template. NiFe-MOF subset of LDH exhibited outperformed OER activity with a lower overpotential of 196 mV and smaller Tafel slope of 48 mV dec(-1)(eta(10)). The conferred higher valence state for Ni3+ and the more carrier density to absorb more OH- ions confirmed by in-situ Raman and density functional theory (DFT) calculation endowed the excellent OER activity, which was expected to endow the self-oxygenation to support the following EF in this system without additional O-2. An electrochemical flow reactor was designed for anodic OER and cathodic EF only at low voltage of 1.6 V. Typically, the in-situ H2O2 yield rate could achieve 27.4 mmol/h at cathodic ORR reaction, which was further activated by Fe2+/Fe3+ cycling for the heterogeneous Fenton reaction. This tandem reactor could remove 96% of ibuprofen (IBF) within 120 min with long-term cycle use. In a word, coupling the OER with EF in a flow reactor has possible application in the fields of sustainable energy and environmental remediation.