Highly Efficient Photocatalytic CO₂ Reduction in Two-Dimensional Ferroelectric CuInP₂S₆ Bilayers

Abstract

Photocatalytic CO2 conversion into reproducible chemical fuels (e.g., CO, CH3OH, or CH4) provides a promising scheme to solve the increasing environmental problems and energy demands simultaneously. However, the efficiency is severely restricted by the high overpotential of the CO2 reduction reaction (CO2RR) and rapid recombination of photoexcited carriers. Here, we propose that a novel type-II photocatalytic mechanism based on two-dimensional (2D) ferroelectric multilayers would be ideal for addressing these issues. Using density-functional theory and nonadiabatic molecular dynamics calculations, we find that the ferroelectric CuInP2S6 bilayers exhibit a staggered band structure induced by the vertical intrinsic electric fields. Different from the traditional type-II band alignment, the unique structure of the CuInP2S6 bilayer not only effectively suppresses the recombination of photogenerated electron–hole (e–h) pairs but also produces a sufficient photovoltage to drive the CO2RR. The predicted recombination time of photogenerated e–h pairs, 1.03 ns, is much longer than the transferring times of photoinduced electrons and holes, 5.45 and 0.27 ps, respectively. Moreover, the overpotential of the CO2RR will decrease by substituting an S atom with a Cu atom, making the redox reaction proceed spontaneously under solar radiation. The solar-to-fuel efficiency with an upper limit of 8.40% is achieved in the CuInP2S6 bilayer and can be further improved to 32.57% for the CuInP2S6 five-layer. Our results indicate that this novel type-II photocatalytic mechanism would be a promising way to achieve highly efficient photocatalytic CO2 conversion based on the 2D ferroelectric multilayers.

Progress on Emerging Ferroelectric Materials for Energy Harvesting, Storage and Conversion

“…Specifically, given the inseparable FE and electrochemical states on its surfaces, which are termed as a ferroionic state, [218][219][220] the diverse coupling effects show prospects not only in suppressing recombination of photo-generated electron-hole pairs, but also in spontaneous solar-to-fuel conversion via a photocatalytic CO 2 reduction reaction (CO 2 RR). [221]…”

“…[289] Apart from these, FE materials such as SrBi 4 Ti 4 O 15 , Bi 2 MoO 6 , and CuInP 2 S 6 have also been used for CO 2 photocatalytic reduction given their tunable activity and selectivity. [221,290,291] Among various layered vdW ferroelectrics, [38], for example, d1T-MoS 2 , GeSn, and CrN, a class of III 2 -VI 3 semiconductors represented by In 2 Se 3 have attracted a great deal of attention due to its exceptional optical properties. [292,293] The In 2 Se 3 is polymorphic with many structural phases (α′, α, β′, β, γ, δ, κ), [294] in which the α, β, and β′ phases are of vdW type and are differed by 2H, 3R, and 1T stacking on the [Se-In-Se-In-Se] quintuple layers (QLs).…”

“…[ 289 ] Apart from these, FE materials such as SrBi 4 Ti 4 O 15 , Bi 2 MoO 6 , and CuInP 2 S 6 have also been used for CO 2 photocatalytic reduction given their tunable activity and selectivity. [ 221,290,291 ]…”

Tailoring the optoelectronic properties and dielectric profiles of few-layer S-doped MoO3 and O-doped MoS2 nanosheets: a first-principles study

“…These optimal heterostructures lead to type II heterojunctions as proposed for other systems. 69,70 In that case, the CB position of FL MoS x O 3-x is located just above the VB of FL MoS 2 which may also provide an optimal situation for a Z-scheme behavior where the…”

An efficient hydrogen evolution photocatalyst of Rh@Cr2O3-loaded PbMoO4 twenty-six facet polyhedrons

“…[21][22][23][24][25] Under such internal electric field (IEF), photogenerated electron-hole pairs will be spatially separated on different crystal planes, suppressing surface recombination and more efficiently leading to a selective regional photoinduced reaction. [26][27][28] Some semiconductors were synthesized with this purpose. Facet-exposed TiO 2 can be obtained by adding Fcontained chemicals, such as HF and NH 4 F. [29][30][31][32] PbMoO 4 is another material with a facet junction, which is synthesized by adding a MoO 3-x template, cetyltrimethylammonium ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP).…”