Piezo-photocatalysis of Sr-doped Bi4O5Br2/Bi2MoO6 composite nanofibers to simultaneously remove inorganic and organic contaminants

Piezo-photocatalysis provides a unique solution for the synergic removal of inorganic and organic pollutants. In this work, a novel strontium-doped bismuth-rich bismuth oxybromide (Bi4O5Br2)/bismuth molybdate (Bi2MoO6) heterojunction catalyst (BOB/BMO/Sr) with superior piezo-photocatalytic effect was hydrothermally synthesized and immobilized to polyacrylonitrile nanofibers (BOB/BMO/Sr/PAN) through electrospinning to simultaneously remove nitrite and 4-chlorophenol (4-CP). The removal rate of nitrite and 4-CP using the optimized BOB/BMO/Sr-5 reached 91.7 % and 100 %, respectively, within 60 min, which were 3.56 and 2.19 times greater than the efficiency of pristine Bi4O5Br2 and Bi2MoO6, respectively. The crystal structure, morphology, chemical composition, optoelectronic and piezoelectric properties of the as-prepared materials were examined through various analyses. The results showed that the improved catalytic activity of BOB/BMO/Sr-5 was attributed to the piezoelectric effect, Sr doping, and heterojunction construction, which improve the charge separation. The BOB/BMO/Sr/PAN-3 nanofibers significantly enhanced the stability and recyclability of the catalysts. The degradation activity was only reduced by 7.3 % for nitrite and 4-CP after five consecutive cycles. Moreover, the removal efficiency of a single pollutant can be promoted by the coexistence of inorganic and organic pollutants. The decisive role of organic pollutants as hole scavengers in the synergistic effect was demonstrated by trapping experiments and density functional theory calculations. Finally, the degradation pathways of 4-CP and nitrite were proposed by product analysis. This work provides a feasible strategy to combine the synergistic effect and piezo-photocatalysis technology to simultaneously remove inorganic and organic contaminants.