Plasma–assisted engineering FeOOH–Nb2O5–CoO heterostructure for efficient and stable seawater electrolysis

A grape-like FeOOH-Nb 2 O 5 -CoO heterostructure engineered on the DBD plasma-modified Co foam for OER. • Plasma treatment endows a special 3D physio-chemical interface for seawater splitting . • The overpotential of FeOOH- Nb 2 O 5 -CoO/PCF for transferring j 1000 is only372 mV 1 M KOH. • DFT calculations disclose the FeOOH-CoO heterointerface lowers the OER energy barrier. Seawater electrolysis represents an attractive approach for producing the high-purity hydrogen. Nevertheless, the high concentration of chloride ions (Cl − ) in seawater leads to severe corrosion of electrodes, posing a major obstacle to the widespread adoption of seawater splitting for green hydrogen generation. Herein, a grape-like iron-niobium-cobalt metal oxide (FeOOH-Nb 2 O 5 -CoO/PCF) is in-situ engineered on the cobalt foam which is modified by a dielectric barrier discharge (DBD) plasma (PCF). Noted that the plasma treatment endows the PCF substrate with critical properties for engineering electrocatalysis: the obtained 3D hierarchical architecture facilitates electrolyte access, the caused interfacial bonding ensures an excellent electrocatalytic durability, and the enhanced surface chemistry accelerates gas bubble release. The optimized FeOOH-Nb 2 O 5 -CoO/PCF electrode achieves an industrial-level current density of 1000 mA cm −2 at a low overpotential of 372 mV in 1 M KOH, and merely 317 mV for transferring a current density of 100 mA cm −2 ( j 100 ) in an aggressive alkaline seawater. Moreover, the FeOOH-Nb 2 O 5 -CoO/PCF maintains an ultra stability for 100 h (1 M KOH) and 317 h (alkaline seawater) with chronoamperometry ( I-t ) tests. Based on Density Functional Theory (DFT) calculations, the constructed heterointerface between CoO and FeOOH phase effectively modulates the electronic configuration of catalyst and lowers the energy barrier of the rate-determining step with the synergistic effect of Nb 2 O 5 , thereby synergistically promoting the oxygen evolution reaction (OER). This work offers a viable pathway for designing highly active and stable electrocatalysts fitting for seawater splitting. A grape-like FeOOH-Nb 2 O 5 -CoO heterostructure is in-situ hydrothermally fabricated on DBD-plasma-etched cobalt foam for a high efficient OER wtih alkaline seawater. In 1 M KOH, it achieves 372 mV at an industrial-level 1000 mA cm −2 with a Tafel slope of 53.8 mV dec −1 . In an alkaline seawater, it requires only 317/359/391 mV at 100/300/500 mA cm −2 . At 500 mA cm −2 , a long-term stability reaches 100 h in 1 M KOH and 317 h in seawater. DFT confirms interfacial Co sites dominate OER activity, while Nb 2 O 5 provides anti-Cl − corrosion protection. This work offers a DBD-assisted pathway for engineering electrocatalysts to achieve a robust seawater electrolysis. Download: Download high-res image (177KB) Download: Download full-size image