Research Article

Defect engineering in layered double hydroxides via surface reconstruction for enhanced oxygen evolution reaction and electrochemical dye degradation

Technological advancements are rapidly transitioning from fossil fuel-based systems to electrified technologies powered by renewable electrons. This swift transformation is driven by innovative materials that lower the cost of renewable electricityenhance storageand expand the range of these emerging applications [1][2]. The development of highly active and cost-efficient electrocatalysts is essential for achieving efficient oxygen and hydrogen production through water electrolysis [3][4].

The most important steps involved in the storage of electrical energy in the chemical forms relies on two fundamental electrochemical reactions [5]: Hydrogen Evolution Reaction (HER) taking place at the cathode and the Oxygen Evolution Reaction (OER) at the anode surface. Among theseOER is a multielectron process to produce molecular O₂ is the bottleneck step which significantly affects the overall efficiency of the system [6][7].

Zinc air battery (ZAB) is an attractive candidate for energy storage and releaseand draws considerable interest in energy storage. The unique advantagessuch as high specific energy densityimproved safetyand environmentally friendly nature of LIBs make them a potential candidate in the pursuit of sustainable energy sources [8].

There are certain challenges associated with the electrochemical efficiency of ZABs. These are the slow reaction kinetics of the oxygen reduction reaction (ORR) and Oxygen evolution reaction (OER)at the air cathodeand thusit constitutes a significant barrier to the massive industrial scale deployment of ZABs [9][10]. Of coursenoble-metal catalystslike Pt/C and RuO2/IrO₂still prove to be the best choice for oxygen electrocatalysts in the cathode. Neverthelessthe packaginghigh costand short lifespan associated with these materials hamper large-scale application of ZAB [11][12].

Concurrentlythe use of a binder in the fabrication of the catalytic electrode can have a detrimental effect on the electrocatalytic activity of the catalytic electrode. It is therefore highly desired to design low-cost and highly stable cathode catalysts for practical applications of ZABs.

The advancement of in situ characterization methods and the comprehensive investigation of OER mechanism have revealed that the majority of transition-metal-based derived electrocatalysts demonstrate a pronounced tendency toward surface reconstruction [13]. The newly reconstructed components are widely recognized as active species; henceaccelerating the rate and enhancing the extent of reconstruction can effectively produce a plethora of genuine active sitesthereby optimizing the efficiency of water electrolysis [14]. Nonethelessonly a limited number of studies have utilized self-reconstruction as a deliberate strategy to synthesize highly active specieslargely owing to its dynamic and complex naturewhich is intricately dependent on the structural adaptability of the precatalysts [15][16]. In this contextthe loosely layered architecture of layered double hydroxidesfeaturing adjustable interlayer anionsmeets the essential requirements for compositional flexibility and is considered highly suitable for self-reconstruction engineering [17][18]. Howeverdue to the substantial activation energy barrier and the highly ordered electron configuration of the pristine LDH surfacethe ensuing formation of AlNiZn-LDH/MOF generally demonstrates constrained intrinsic activity. Thusinvestigating the dynamic reconfiguration mechanisms of catalysts to promote rapid structural transformation and unveiling the true active species is instrumental in precisely designing highly efficient OER electrocatalysts.

At the same timeLDHs serve as versatile precursors for synthesizing MOFswith their appropriate interlayer spacing promoting the linkage of organic ligands to metal ions [19]. Neverthelesselaboration on the construction of MOF/LDH composites through surface reconstruction processes of LDH is not well explored in the literature. Indeedthe structure with reduced orderor less ordered atomic patterns and more unsaturated sitessuch as partially etched LDHs can significantly improve active site exposure [20]. The ultrathin TMOFNs have drawn immense interest in electrocatalysis because of abundant exposed active sitesthe synergistic effect from trimetallic elementsextremely thin nanosheet structures coupled with large surface areaand considerable conductivity. Their superior electron transport capabilities particularly stem from their atomic-scale thinness [21]. Thereforethe fabrication of supported ultrathin TMOFNscoupled with a comprehensive knowledge of interfacial interactions taking place between functional substrates and MOF-based catalystscould pave the way for designing heterocomposites that are liberated from the limitations imposed by significant thermodynamic instability [22][23]. Henceit is anticipated that the surface engineering of LDH nanosheets to construct MOFs can effectively harness the synergistic effects of both materialsleading to a substantial enhancement in OER activity [24].

In this studywe report a highly efficient and robust bifunctional electrocatalyst via the surface reconstruction strategy using organic ligands as etchants from LDHs. The intrinsic properties of LDHs and surface-constructed MOFs efficiently enhanced OER performance and electrochemical degradation of the representative cationic dyeCrystal Violet (Cry-V). This study improves the electrocatalytic performance of LDH/MOF hybrid materials and offers a promising solution for wastewater treatment.