Defective-tin-oxide wrapped gold nanoparticles with strong sunlight harvesting and efficient charge separation for photocatalysis.

• Au@D-SnO 2 NPs are prepared creatively by alloying and selective-oxidation. • The NPs show strong sunlight harvesting and efficient charge separation. • The NPs show efficient photocatalytic-removal of NH 3. Strong sunlight harvesting and efficient charge separation are of great significances for solar energy utilization of metal oxides, but it is a challenge to realize these two aspects simultaneously. Here, we strategize oxygen-vacancy-rich (or defective)-SnO 2 wrapped gold nanoparticles (Au@D-SnO 2 NPs) for this. The designed NPs are fabricated just by adding precursors into boiling pre-prepared Au colloidal solution and then re-dispersing the reacted NPs in water, based on surface alloying and selective oxidation. Typically, the fabricated Au@D-SnO 2 NPs (with 12 nm thick shell) exhibit strong absorption in full solar spectrum (200–2000 nm) with an energy absorption efficiency as high as 84%. Meanwhile, the photocurrent response of the typical NPs is 2.3 and 13.6 times as high as that of Au@SnO 2 NPs (with poor oxygen vacancies) and commercial SnO 2 NPs, respectively, showing efficient charge separation. Such excellent performance is attributed to the synergistic effect of surface plasmon resonance (SPR) of the Au core and the band gap narrowing induced by the abundant oxygen vacancies. Further, the excellent photocatalytic performance of the Au@D-SnO 2 NP catalyst has been demonstrated via exemplary photocatalytic removal of gaseous ammonia. The catalytic rate is about 4.2 and 25 times as high as that of the Au@SnO 2 NP and the commercial SnO 2 NP catalysts, respectively. It is expected that such excellent photocatalytic performance will also be obtained on other defective oxides wrapped metal structures. This work provides a preparation method for Au@D-SnO 2 NPs, which can be used for efficient solar energy utilization. [ABSTRACT FROM AUTHOR]