[Ta6O19]8−-mediated interfacial OH− supply for efficient seawater electrolysis

Seawater electrolysis is promising yet challenging, as the rapid multi-step deprotonation process of oxygen evolution reaction (OER), along with the Ca²⁺, Mg²⁺ ions, would deplete the accessible OH^- ions near the catalyst-electrolyte interface. Herein, we present the hexatantalate [Ta₆O₁₉]^8- ({Ta₆}), a robust H-bond acceptor (HA) to customize the interfacial H-bonds and charge transfer of the layered metal organic framework (MOF) electrocatalyst, for efficiency alkaline seawater OER. Experimental findings reveal that the {Ta₆} cluster reconstructs the H-bond networks both in the MOF interlayers and at the catalyst-electrolyte interface, liberating more free OH^- to penetrate the Helmholtz plane and adsorb onto the catalyst surface. The increased accessible OH^- deepens the partial reconstruction degree of the MOF into active components. Besides, the {Ta₆} cluster modulates the electronic configuration of Ni active sites in the MOF framework, enabling the synthesized R-MOF-Ta₆/NF electrocatalyst to achieve a low overpotential of 235 mV at a current density of 10 mA cm^-2. Moreover, the anion exchange membrane (AEM) electrolyzer utilizing the R-MOF-Ta₆/NF anode catalyst could operate 195 h at industrial current density (≥200 mA cm^-2). This study presents a neoteric strategy to enhance the performance of layered catalysts for seawater OER.