Synthesis and CO₂ Photoreduction of Lead-Free Cesium Bismuth Halide Perovskite Nanocrystals

Abstract

The photoreduction of CO 2 into renewable fuels is a promising approach to solve the global energy and environmental crisis. All-inorganic bismuth (Bi) halide perovskite nanocrystals (NCs) have emerged as an appealing photocatalyst for visible-light-driven CO 2 reduction, but they still have low photocatalytic activity. Herein, a set of lead-free and stable Cs 3 Bi 2 X 9 (X = Cl, Cl 0.5 Br 0.5 , Br, Br 0.5 I 0.5 , I) perovskite NCs were explored for the photocatalytic reduction of CO 2 to CO at the gas− solid interface. In all of the recorded perovskite NCs, the as-synthesized Cs 3 Bi 2 (Br 0.5 I 0.5 ) 9 showed the highest efficiency of CO 2 -to-CO conversion producing 54 μmol g −1 of CO yield under visible-light irradiation for 3 h. The strategy we proposed may bring up new opportunities for an efficient photocatalytic CO 2 reduction of lead-free perovskite NCs.

Lead-Free Cs2TeX6 (X = Cl, Br, and I) Perovskite Microcrystals with High Stability for Efficient Photocatalytic CO2 Reduction

“…The artificial photoconversion of CO 2 into available fuels and chemicals has been considered as a prospective tactic of mitigating the energy crisis and climate change issues. − Compared with other approaches, such as thermolysis, electrocatalysis, and plasma catalysis, photocatalysis holds the advantages of low cost and direct use of renewable solar energy. , To date, many previous works have reported efficient photocatalysts for CO 2 reduction, for example, transition metals, molecular complexes, conducting polymers, Au nanoclusters, inorganic semiconductors, metal–organic backbones, and heterojunctions. − The lead halide perovskite ABX 3 (A = Cs, MA, and FA; X = Cl, Br, and I) materials possessed many glorious optical properties, including strong absorptivity, easy tunability of the absorption region, and large nonequilibrium carrier lifetime, − resulting in their wide utilization in solar cells, − light-emitting diodes, and photodetectors . Recently, the lead halide perovskites have been investigated for solar water splitting, , dye photodegradation, − and CO 2 photoreduction. − However, they generally encounter the poor stability and lead toxicity, restricting their large-scale practical applications . Consequently, exploring the highly stable halide perovskites without the lead element has become a new chance to develop novel photoelectronic materials and devices.…”

Pb-free halide perovskites for solar cells, light-emitting diodes, and photocatalysts

“…226 As a result, the Cs 2 AgBiI 6 NCs shows the best photoreduction activity with a CO yield of 18.9 μmol g −1 under visible light irradiation (λ ≥ 420 nm, 300 W Xe lamp) within 3 h. Similarly, the bandgap of the 2D layered perovskite Cs 3 Bi 2 X 9 NCs decreases from 3.08 to 2.01 eV as halide X goes from Cl − to I − . 227 The highest CO yielding speed is 54 μmol⋅g −1 when X = Br 0.5 I 0.5 , compared to the 48 μmol g −1 when X = Cl 0.5 Br 0.5 and 11 μmol g −1 when X = I under visible-light irradiation (λ ≥ 420 nm, 300 W Xe lamp) for 3 h. The suitable band structure, wide light absorption range, large photocurrent, and small impedance of Cs 3 Bi 2 (Br 0.5 I 0.5 ) 9 contribute to its greater activity in gas-solid interface than in the majority of the liquid-phase CO 2 reduction systems.…”

Cs2AgBiBr6 Double Perovskites as Lead‐Free Alternatives for Perovskite Solar Cells?

“…[73] While this material readily forms the ternary compound Cs 3 Bi 2 I 9 , which has been investigated in the community already and expresses poor optoelectronic and photovoltaic properties, [74] the quarternary structure of Cs 2 AgBiI 6 can only be stabilized in nanocrystals after complicated anion exchange procedures with methylsilane compounds. [75,76] A promising procedure to stabilize the iodine perovskite was initially shown by the Mitzi group, where large cations have been implemented in the perovskite structure to form a 2D compound. [77] Here, (bisaminothyl)bithiophene was implemented to form (AET) 2 AgBiI 8 which shows a drastic change in the bandgap by means of energy reduction (2.0 eV) and nature (transition from indirect to direct) which was then realized by other groups using different spacer cations.…”