Boosting the efficient alkaline seawater oxygen evolution reaction of iron oxide hydroxide via plasma-induced oxygen defect engineering†

Abstract

Obtaining hydrogen through direct decomposition of seawater is highly significant for alleviating the increasing shortage of freshwater resources. Nonetheless, a major obstacle to the oxidation of saltwater is the severe corrosion of anodes by Cl⁻ ions. In this work, a wet chemical technique and argon plasma treatment were used to obtain defect-rich FeOOH/SS electrodes for the OER in a basic electrolyte and simulated seawater. The findings from EPR and XAFS showed that a significant number of oxygen vacancies were generated through the plasma treatment. These vacancies promoted the activation of lattice oxygen during the oxidation of water. The findings showed that plentiful oxygen vacancies in P-FeOOH/SS provided a substantial number of active sites and facilitated efficient electron transfer, both of which greatly increased OER activity. Notably, when the electrolyte was simulated seawater (1.0 M KOH and 0.5 M NaCl), the overpotential reached 278 mV at 10 mA cm⁻². Under these conditions, the Tafel slope was measured at 32.66 mV dec⁻¹. Furthermore, the stability was maintained at 50 mA cm⁻² for more than 100 hours. Theoretical calculations showed that the high catalytic activity was primarily due to the positive effects of oxygen defects on the electron density and the d-band center of the active site. This research presented a straightforward approach for the development of efficacious defect-rich electrodes for alkaline seawater electrolysis.