Ab initio study on photocatalytic properties of PtSSe-WXY Janus heterostructures

TL;DR

This study demonstrates that Janus PtSSe–WXY van der Waals bilayers are promising photocatalysts for HER, OER, and CO$_2$ reduction. Using ab initio DFT with PBE-D3 and HSE06, the authors explore four interface configurations and five stacking orders across PtWSSe, PtWSTe, and PtWSeTe bilayers, evaluating band-edge alignments, stability via layer-binding energies, and thermal robustness via AIMD; optical absorption calculations confirm visible-light activity. PtWSeTe-based bilayers, particularly IC1-S2 and IC4-S2, show favorable band alignments for HER and CO$_2$ reduction, with IC4-S2 offering a type-II arrangement that enhances charge separation, while OER is less favorable unless strain shifts the VBM appropriately. Band-edge tuning by biaxial strain further expands photocatalytic possibilities, enabling selective activation of redox reactions: compressive strain can shift certain configurations toward OER or HER/CO$_2$ reduction, and visible absorption persists under strain. PtWSSe is less viable due to positive layer-binding energy, whereas PtWSTe exhibits narrow gaps that may be advantageous for thermoelectrics or infrared photovoltaics, highlighting strain engineering as a practical design knob for these heterostructures.

Abstract

Semiconductor photocatalysis offers a sustainable route for converting solar energy into chemical energy, enabling the production of clean fuels and valuable chemical products. To this aim, we explore van der Waals heterostructures made up of Janus PtSSe and WXY (X, Y $=$ S, Se, Te and X $\neq$Y), in the context of photocatalytic applications. The redox capabilities of various heterostructure configurations (atom facing types and stacking orders) are evaluated by aligning the absolute band edge positions with respect to redox potentials of hydrogen and oxygen evolution reaction (HER and OER) and CO$_2$ reduction reactions. The stability of photocatalyst candidates are checked by layer binding energy calculations and ab initio molecular dynamics simulations. The optical absorption spectra suggest good light absorption in the visible range. Further, strain engineering is applied as a way to tune band edges and evaluate the possible use of the heterostructures as photocatalysts. This study shows that van der Waals heterostructure bilayers composed of Janus PtSSe and WSeTe in specific geometric configurations can be potential materials as photocatalysts for HER, OER and CO$_2$ reduction reactions. Finally, we suggest that, although systems made up of PtSSe and WSTe cannot be used for photocatalytic applications, they can be explored for applications in thermoelectric energy conversion or infrared photovoltaics.

Figures (16)

• Figure 1: Model geometry of three HSs considered in this work: (a) PtSSe-WSSe (b) PtSSe-WSTe and (c) PtSSe-WSeTe (top view). Fig. (d)-(f) show the respective side views.
• Figure 2: The four possible atom facing configurations, IC1-IC4 ((a)-(d)) in the case of PtWSSe HS. Similarly, four possible ICs are considered in case of other two HSs.
• Figure 3: Variation of total energy of the system, average bond distance (Avg. bond dist.) and horizontal distance between layers (Horizon. d$_{\mathrm{L1-L2}}$) as a function of time. Left and right panels show the results for PtWSeTe-IC1-S2 and PtWSeTe-IC4-S2 systems, respectively.
• Figure 4: Electronic band structure of (a) PtWSeTe-IC1-S2 and (b) PtWSeTe-IC4-S2 heterostructures calculated using the HSE06 functional.
• Figure 5: Layer projected band structures of (a) PtWSeTe-IC1-S2 (b) PtWSeTe-IC4-S2 systems. Red and green circles represent projection onto WSeTe and PtSSe component monolayers, respectively; larger circles indicate larger component contributions.