Yolk-shell nanomaterials for advanced oxidation processes

Advanced oxidation processes (AOPs) are generally regarded as promising effective decontamination technologies for nonbiodegradable, hazardous or refractory pollutants. The reactive species of AOPs suffer from ultrafast self-quenching in the bulk aqueous phase because of their extremely short lifetime and consumption by coexisting substances in actual water matrices. Yolk-shell nanomaterials (YSNMs) with a typical core@void@shell architecture are widely used as AOP nanoreactors to host chemical reactions and alter chemical reactivity via confinement effects. All components of YSNMs, including voids, shells and cores, synergistically contribute to effective organic pollutant degradation with outstanding activity and selectivity. YSNMs have been widely used as activators of different peroxides, including hydrogen peroxide, peroxymonosulfate, persulfate and peroxymonocarbonate, due to their improved reactivity, selectivity, stability and easy recovery. YSNMs provide a robust platform for photochemical wastewater remediation, which can couple with surface plasmon resonance, band gap engineering, photon up-conversion, heterojunction and cocatalyst engineering. YSNM photocatalysts exhibit superior activity compared with their counterparts because of multiple virtues, such as efficient light harvesting, sufficient active sites, extended photo response, improved separation efficiency of carriers and prolonged lifetime of photogenerated carriers. The nanoelectrode with a YSNM structure can improve electrochemical degradation efficiency via combining the advantages of both nanosized building subunits and hollow architectures. The challenges and prospects of YSNMs for AOPs are also addressed to stimulate potential breakthroughs.