Significantly enhanced photocatalytic activity by surface acid corrosion treatment and Au nanoparticles decoration on the surface of SnFe2O4 nano-octahedron

• Au deposited surface modified Au-S-SFO were synthesized through GLIP acid treatment. • Surface anchored functional groups –OH, -SO 3 H, and –NH enhanced Au dispersion over SFO. • Photoactivity of Au-S-SFO was enhanced by improved carriers separation and transfer through Au SPR. • CO 2 was efficiently reduced to CO, CH 4 and H 2 of yield rate 11.56, 0.75 and 1.21 μmolg −1 h −1 by Au-S-SFO. • Photocatalytic degradation of CTC was>2.5 time than that of pure SFO. The synergy effect of surface modifications using acid treatment and noble metal (Au) deposition on the efficiency of SnFe 2 O 4 (SFO) nano-octahedron photocatalyst has been investigated. Inorganic acids (H 2 SO 4 and HNO 3 ) were employed to compare the effects of different acids. It has been found that after corrosion treatment using H 2 SO 4 and deposition of Au nanoparticles, SnFe 2 O 4 nano-octahedron (Au-S-SFO) showed significantly enhanced photocatalytic activity under simulated light irradiation. Au-S-SFO was characterized by XRD, XPS, EDS, FTIR, Uv–vis-DRS, SEM, PL and EIS analysis. The mechanism for the photocatalytic chlortetracycline (CTC) degradation and CO 2 reduction was investigated by the scavenger tests. The stability of Au-S-SFO was confirmed by continuously repeated tests followed by XRD and TEM analysis. The surface corrosion treatment of SFO octahedron with H 2 SO 4 could produce hydroxyl group (–OH) and sulfonic acid group (-SO 3 H) as reaction sites. These active sites not only enhanced the Au nanoparticles deposition to the acid treated SFO surface, but also acted as the Brønsted acid sites which enhance the water adsorption and provide protons for CTC degradation and CO 2 reduction. These effects improved the carrier separation and transfer efficiency. In addition, the photocatalytic efficiency was further enhanced by the surface plasmon resonance (SPR) effect of Au nanoparticles deposited on the surface of acid treated SFO. As a result of the synergy effect of both acid treatment and SPR effect from the Au NPs, Au-S-SFO exhibited >2.5 times higher photocatalytic CTC degradation efficiency than pure SFO. Furthermore, Au-S-SFO displayed the highest CO 2 reduction activity with 2.81, 1.92, and 2.69 times higher evolution rate for CO, CH 4 and H 2 , respectively, than that of pure SFO.