Construction of core–shell coordination sponge-Fe0@Cu-Pd trimetal for high efficient activation of room-temperature dissolved ambient oxygen toward synergistic catalytic degradation of tetracycline and p-nitrophenol

Room-temperature ambient air is cheap and easy to obtain, hence the application of room-temperature ambient air as sole oxidant for pollutant degradation is extremely fascinating. In this work, core–shell coordination sponge-Fe0@Cu-Pd trimetal catalyst was synthesized via a simple step displacement plating process employing first displacement of Cu and the subsequent displacement of Pd, and applied as heterogeneous catalyst for synergistic catalytic degradation of composite pollutants including TC and PNP. The prepared s-Fe0@Cu-Pd trimetal sample was characterized with XRD, SEM, TEM, VSM and XPS. The characterization results revealed the obtained s-Fe0@Cu-Pd trimetal sample was a 20 ∼ 30 nm core–shell spherical morphology composed of Fe0 aggregates core wrapped by a Cu-Pd shell layer. The obtained sponge-Fe0@Cu-Pd trimetal catalyst could efficiently activate room-temperature dissolved ambient oxygen and achieve the largest TC removal rate of 99.08 % and PNP removal rate of 97.16 % as well as the biggest removal rate constant of 8.76 min−1 for TC degradation and 7.55 min−1 for PNP degradation within 60 min at experimental conditions: [TC] = 30 mg/L, [PNP] = 30 mg/L, [Catalyst] = 25.52 g/L, pH = 3, 298 K ascribed to the strongest oxidation and reduction ability confirmed by CV characterizations, the lowest charge transfer and contact resistance affirmed by EIS measurements, the strongest O2 activation ability verified by O2-TPD characterizations and DFT analyses, the largest external surface area and mesoporous volume validated by Nitrogen adsorption and desorption characterizations as well as the synergistic catalysis effect for wrapped Cu and Pd. Quenching experiments and EPR characterizations revealed that •OH, •O2−, 1O2 and •H are all the reactive species and meanwhile •O2− served as the main reactive oxygen species. Furthermore, possible mechanisms of TC and PNP degradation via sponge-Fe0@Cu-Pd trimetal catalyst were proposed.