Title : Untapped potential of lead-free halide perovskites for synergistic biomass valorization and solar fuel generation
Abstract:
Hybrid halide perovskites (HHPs), whose every branch generates intrusiveness, have been utilized in solar cells from a wider perspective. However, the inclusiveness of employing HHP as a photocatalyst is still in its initial stage. We have explored the so far undesirable material, MA2SnBr6 synthesized from MASnBr3 and discovered a new vacancy-ordered MA2SnBr6 perovskite as a potential photocatalyst for efficient solar-driven C(sp3)?H activation of cyclohexane and toluene under ambient conditions. The as-synthesized MASnBr3 and its oxidized form having different ratios of Sn2+ and Sn4+ were subjected to cyclohexane oxidation and it was observed that the completely oxidized form i.e. MA2SnBr6 gave the highest yield of cyclohexanol and cyclohexanone.1 Further, we have addressed four major key challenges in the domain of halide perovskites i.e. toxicity, stability, reusability, and efficiency of halide perovskites. To tackle these issues, we synthesized a vacancy-ordered HHP, specifically methyl ammonium tin bromide quantum dots (MA2SnBr6 QDs) directly from its raw precursors this time, which had not been explicitly synthesized so far. MA2SnBr6 was synthesized through a greener approach, a simple yet effective solvent-free mechanochemical synthesis at room temperature without the use of additional capping agents. Interestingly, the synthesized MA2SnBr6 QDs exhibit stability in air and moisture, addressing a common issue with HHPs. Surprisingly, we also discovered that these MA2SnBr6 QDs are stable in polar solvents such as isopropanol, ethanol, and acetonitrile, overcoming a major challenge typically encountered with halide perovskites. The air and moisture-stable MA2SnBr6 QDs were applied for photocatalytic CO2 conversion. The icing on the cake is the simultaneous conversion of biomass-derived alcohol to valuable chemicals which was not attempted previously with CO2 reduction. The yield of the CO and CH4 is higher than the so far reported perovskite used for photocatalytic CO2 reduction.2 Moreover, compared with the complex photocatalytic system previously reported, our single catalytic (MA2SnBr6) system presented impressive results for simultaneous biomass-derived alcohol oxidation with CO2 reduction.
