Identification of Halogen-Associated Active Sites on Bismuth-Based Perovskite Quantum Dots for Efficient and Selective CO₂-to-CO Photoreduction

Abstract

All-inorganic Pb-free bismuth (Bi) halogen perovskite quantum dots (PQDs) with distinct structural and photoelectric properties provide plenty of room for selective photoreduction of CO 2 . However, the efficient conversion of CO 2 -to-CO with high selectivity on Bi-based PQDs driven by solar light remains unachieved, and the precise reaction path/ mechanism promoted by the surface halogen-associated active sites is still poorly understood. Herein, we screen a series of nontoxic and stable Cs 3 Bi 2 X 9 (X = Cl, Br, I) PQDs for selective photocatalytic reduction of CO 2 -to-CO at the gas−solid interface. Among all the reported pure-phase PQDs, the assynthesized Cs 3 Bi 2 Br 9 PQDs exhibited the highest CO 2 -to-CO conversion efficiency generating 134.76 μmol g −1 of CO yield with 98.7% selectivity under AM 1.5G simulated solar illumination. The surface halogen-associated active sites and reaction intermediates were dynamically monitored and precisely unraveled based on in situ DRIFTS investigation. In combination with the DFT calculation, it was revealed that the surface Br sites allow for optimizing the coordination modes of surfacebound intermediate species and reducing the reaction energy of the rate-limiting step of COOH − intermediate formation from • CO 2 − . This work presents a mechanistic insight into the halogen-involved catalytic reaction mechanism in solar fuel production.

Solar fuels: research and development strategies to accelerate photocatalytic CO2 conversion into hydrocarbon fuels

“…For these structures, high photocatalytic CO 2 conversion can be achieved through the excellent light harvesting, satisfactory charge carrier density, and abundant surface sites. [147][148][149][150][151][152] Among such structures, the most extensively used are carbon QDs (CQDs), which exhibit a broad light absorption spectrum due to p-plasmon absorption in the core carbon nanocrystals, thereby enabling the pp* transition of conjugated carbon atoms in the UV-visible region. [153][154][155] It can be utilized not only in CQDs but also in semiconductor QDs and is advantageous for multi-electron and proton reduction.…”

Halide perovskites for light emission and artificial photosynthesis: Opportunities, challenges, and perspectives

“…For example, the Cs 3 Bi 2 X 9 (X = Cl, Br, I) QDs synthesized by antisolvent method achieved selective photocatalytic CO 2 reduction to CO at the gas‐solid interface, in which the Cs 3 Bi 2 Br 9 exhibited the highest CO 2 to CO conversion efficiency reaching 134.76 μmol g −1 h −1 with 98.7% selectivity 135 . The in situ DRIFTS and DFT calculation revealed that COOH − was the primary intermediate of CO 2 photoreduction, and Br sites could lower the reaction energy of the rate‐limiting step of COOH − formation from • CO 2 − through optimizing the coordination modes of intermediate species on the surface 135 . Again, Chen et al 136 reported that the CsPbBr 3 perovskite single crystals are capable to perform photocatalytic CO 2 reduction directly on their surface (Figure 5K).…”

“…Since the photocatalytic CO 2 reduction involves the reaction of multiple protons and electrons, the reaction mechanism is very complex. Recently, based on Cs 3 Bi 2 X 9 (X = Cl, Br, I) QDs, Sheng et al 135 unraveled the surface halogen‐associated active sites and reaction intermediates (COOH − ) for selective photoreduction of CO 2 to CO by combining in situ DRIFTS investigation with DFT calculation. They found that the surface Br element can modulate the coordination modes of intermediates on the surface and reducing the reaction energy of the rate‐limiting step of COOH − formation from • CO 2 − .…”

Review on Bismuth‐Based Photocatalyst for CO2 Conversion

“…Combining BiVO 4 QDs showed much enhanced photoreduction rate converting CO 2 into CO and CH 4 owing to the combination between large specific surface area and prolonged photogenerated charge lifetime. Dong et.al prepared a series of Cs 3 Bi 2 X 9 (X=l, Br, I) perovskite quantum dots (PQDs) for selective CO 2 photoreduction into CO [27e] . The Cs 3 Bi 2 Br 9 PQDs exhibit the highest CO conversion rate (134.76 μmol g −1 , 98.7% selectivity, AM 1.5G light irradiation).…”