In Situ Nanoconfinement Catalysis for Highly Efficient Redox Transformation

The rapid reduction of Cr(VI) across a wide pH range, from acidic to alkaline pH conditions to stable Cr(III) species for efficient remediation of Cr(VI) pollution, has long been a challenge. Herein, we propose a new concept of in situ nanoconfinement catalysis (iNCC) for highly efficient remediation of Cr(VI) by growing nanosheets of in situ layered double hydroxide (iLDH) on the surface of Al-Mg-Fe alloy achieving chemical reduction rates of >99% in 1 min from pH 3 to 11 for 100 mg L^-1 Cr(VI) with a rate constant of 201 h^-1. In stark contrast, the reduction rate is less than 6% in 12 h with a rate constant of 0.77 h^-1 for the pristine Al-Mg-Fe alloy. The ultrafast reduction of Cr(VI) is most likely attributed to the synergistic catalysis of Al₁₂Mg₁₇ and Al₁₃Fe₄ and nanoconfinement of MgAlFe-iLDH and superstable mineralization of Cr(III) by MgAlCr^III- and MgFeCr^III-iLDHs. This study demonstrates the potential of in situ nanoconfinement catalysis on redox transformation for environmental remediation.