Engineering Pd Nanostructures on Hierarchical Flower‐Like Alumina Nanosheets for the Efficient Catalytic Reduction of 4‐Nitrophenol

ABSTRACT The persistence of 4‐nitrophenol (4‐NP), a toxic nitroaromatic pollutant, poses serious environmental and health risks, making its catalytic reduction to 4‐aminophenol (4‐AP) both an urgent challenge and an industrially valuable transformation. Here, we report palladium nanostructures (nanocubes and nanoparticles) supported on nanosheet‐assembled alumina (NA‐Al 2 O 3 ) as highly efficient catalysts for this reaction. The unique flower‐like hierarchical morphology of NA‐Al 2 O 3 provides high surface area, accessible mesoporosity, and abundant anchoring sites, enabling uniform dispersion and stabilization of Pd species. To decouple morphology and support effects, two key comparisons were performed. First, Pd nanocubes (PdNC@NA) were evaluated against size‐matched Pd nanoparticles (20PdNP@NA) on the same NA‐Al 2 O 3 support, where PdNC@NA achieved faster 4‐NP reduction (9 min vs. 13 min), highlighting the catalytic advantage of exposed {100} facets of PdNCs. Second, PdNP@NA was compared with PdNP@CA on commercial Al 2 O 3 , where PdNP@NA completed the reaction significantly faster (5 min vs. 19 min), demonstrating the superior textural properties of NA‐Al 2 O 3 over conventional support. Kinetic analyses confirmed pseudo‐first‐order behavior with high apparent rate constants for all catalysts. Moreover, PdNC@NA retained both activity and morphology over five consecutive cycles, demonstrating excellent stability under catalytic conditions.