Ni@NiOOH co-catalyst-enhanced preferentially oriented TiO2 nanotubes for highly efficient seawater splitting

Abstract

The corrosive environment of seawater, particularly the presence of chloride ions (Cl⁻), poses significant challenges to achieving efficient and stable photoelectrochemical (PEC) seawater splitting. This study addresses these challenges by developing a photoanode featuring Ni@NiOOH co-catalyst-enhanced preferentially oriented TiO₂ nanotubes (TNTs). The in-situ formation of NiOOH on Ni nanocrystals addresses the poor conductivity of NiOOH through the metallic nature of Ni, while NiOOH compensates for the weak OER activity of Ni nanocrystals. Moreover, the Ni@NiOOH core-shell structure exhibits excellent stability. By depositing Ni nanocrystals on nanotube arrays with varying [001] orientation strengths, the interaction between Ni and the nanotubes was systematically investigated. The results demonstrate that Ni nanocrystals exhibit the strongest interaction with highly [001]-oriented TNTs, which consequently delivers the most enhanced photoelectrochemical (PEC). The core-shell-structured Ni@NiOOH co-catalyst, formed through the pulsed galvanostatic deposition of Ni nanocrystals on TNTs with a strong [001] orientation, significantly enhanced the oxygen evolution reaction (OER) activity and charge carrier separation efficiency. This synergistic effect resulted in a 3.5-fold increase in the photocurrent density and exceptional PEC durability, with only 16 % degradation over 9 h. The unique structure of Ni@NiOOH combines high conductivity with superior catalytic activity, providing an advanced approach for efficient and stable seawater splitting.