Mechanochemical synthesis of MAPbBr3/carbon sphere composites for boosting carrier-involved superoxide species.

Lead halide perovskites MAPbX3 (MA = CH3NH3 or Cs; X = I, Br, Cl) are well considered to be potential candidates for photocatalytic reaction due to its excellent photoelectrical properties, but they still suffer from the low charge separation efficiency and slow catalytic reaction dynamics. To tackle the drawbacks, herein, MAPbBr3/carbon sphere (CS) composite photocatalysts using glucose as the carbon source were elaborately designed and fabricated via a dry mechanochemical grinding process. The interfacial interaction Pb-O-C chemical bonds were constructed between MAPbBr3 and the carbon sphere surface containing organic functional groups. By optimizing the content of CSs, the enhanced photocatalytic degradation kinetic rate of Malachite Green (MG) pollutants (92% within 20 min) for MAPbBr3/CSx (x = 17 wt.%) is about 3.6-fold of that for pristine MAPbBr3, which is attributed to the corporative adsorption and enhanced carrier transportation and separation of MAPbBr3/CSx. Furthermore, the possible degradation mechanism was proposed on basis of the electrochemical, mass spectrometry and optical characterization results. Owing to the robust interfacial interaction, effective electron extraction rate (ket = 4.6 × 107 sec-1) from MAPbBr3 to CS can be established, which driven oxygen activation where superoxide radicals (•O2-) played an important role in MG degradation. It is expected that mechanochemistry strategy may provide a new route to design efficient lead halide perovskite-carbon or metal oxide or sulfide composite photocatalysts.