In Situ Construction of Hierarchical CuCo Layered Double Hydroxide Nanoarrays: Synergistic Enhancement and Mass Transfer Intensification in Electrocatalytic Nitrate-to-Ammonia.
Abstract
Electrocatalytic nitrate reduction to ammonia provides a sustainable route for nitrate-containing wastewater remediation and energy conversion. The development of nonprecious metal electrocatalysts that simultaneously achieve high ammonia selectivity, fast production rate and long-term stability still remains challenging. This study constructs hierarchical Cu-Co layered double hydroxide nanoarrays directly grown on nickel foam (CuCo LDH/NF) via a facile one-step hydrothermal method. The present work highlights two coupled core innovations: the Cu-Co bimetallic tandem catalytic mechanism and the mass transfer enhancement originating from the interlaced three-dimensional nanoarray architecture. Benefiting from electronic synergistic effect between Cu and Co, a tandem catalytic pathway is formed to suppress intermediate byproduct accumulation. Meanwhile, the in situ grown interlaced nanosheet arrays formed a hydrophilic, hierarchically porous three-dimensional open network. This architecture significantly enlarged the electrochemically active surface area (7.7 mF cm-2) and enhanced mass transfer efficiency. Owing to such dual synergistic optimization of catalytic active sites and mass transfer pathways, the as-prepared CuCo LDH/NF delivers a high NH3 Faradaic efficiency of 96.78% and an NH3 yield rate of 7.8 mg h-1 cm-2 at -0.9 V vs RHE in neutral electrolyte, alongside robust stability over 15 h continuous electrolysis. Kinetic analyses reveal that the nitrate reduction reaction follows an apparent pseudo-first-order model, and the reaction rate constant reaches 0.0521 min-1, which is approximately 23-fold higher than monometallic Co LDH catalyst. Furthermore, the catalyst exhibits good adaptability toward varied nitrate substrate concentrations within a certain range. This work offers a dual-regulation strategy combining electronic-structure modulation and mass-transfer intensification for designing high-performance nitrate-reduction electrocatalysts, and provides experimental insights for practical treatment of nitrate polluted wastewater.
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