Synthesis of CuNiSn LDHs as highly efficient Fenton catalysts for degradation of phenol

A series of CuNiSn ternary layered double hydroxides (LDH) were synthesized as catalysts for degradation of phenol via Fenton reaction. At Cu/Ni ratios above 0.2, copper chloride hydroxide co-exists with LDH. Multivalent Cu+/Cu2+, Ni2+/Ni3+ and Sn2+/Sn4+ ions are present in LDH due to the electron transfer between metals in brucite-like sheets. The catalytic activity varies directly with the Cu+ percentage, and the maximum activity is achieved at Cu/Ni/Sn ratio of 1/2/0.75. This catalyst (Cu1Ni2Sn0.75) can mineralize 97.8% phenol under mild conditions and shows good stability. Multivalent Cu, Ni and Sn cations in LDH could construct a closed electron cycle. This allows the rapid regeneration of Cu+ active species through electron transfer within LDH rather than through slow Fenton-like reaction, as what usually happens in conventional Fenton catalysts. In addition, a positive synergistic effect between copper chloride hydroxide and LDH is observed in Cu1Ni2Sn0.75, favoring the formation of Cu+.