A nanoporous Ni(OH)₂ interlinked Co₃O₄ heterojunction: a novel approach to chromium(vi) detection

The present study broadly explores the synthesis, structural characteristics, and electrochemical performance of a nanoporous Ni(OH)₂/Co₃O₄ heterojunction engineered for efficient enzymatic sensing of hexavalent chromium Cr(vi). The synthesized heterostructure consists of a porous Ni(OH)₂/Co₃O₄ matrix (nanopores, with dimensions approximately ranging from 6 to 10 nm) intimately coupled with evenly dispersed Co₃O₄ nanocrystals, forming a well-integrated interface that enables strong synergistic redox coupling and rapid electron transport across the junction. The nanoporous framework significantly increases the electrochemically active surface area offering abundant catalytically active sites and facilitates improved transport of electrolytes. Simultaneously, the heterojunction ensures continuous conductive pathways, thereby minimizing charge-transfer resistance and enhancing overall electron mobility. The combined structural and electronic advantages translate into markedly improved sensitivity, catalytic activity, and operational stability for enzymatic Cr(vi) detection with a limit of detection (LOD) of 39 nM. Overall, the results underscore the significant role of heterojunction engineering in enhancing the performance of metal hydroxide-oxide materials for advanced environmental sensing applications.