Insights into the OER, ORR, and HER Activity of a New MXene-Family SnSiGeN4 Photocatalyst for Water Splitting: A First-Principles Study

TL;DR

This paper tackles the search for cost‑effective, efficient photocatalysts for water splitting by examining a newly predicted SnSiGeN4 MXene‑family monolayer with first‑principles methods. Using unrestricted hybrid DFT with D3 dispersion in CRYSTAL17, it maps structural, electronic, vibrational, and optical properties, showing a direct, tunable band gap and strong UV–visible absorption, along with IR/Raman fingerprints confirming stability and active sites. The authors then perform Gibbs‑energy analyses for OER, ORR, and HER across multiple candidate active sites, finding low overpotentials (e.g., η_OER ≈ 0.48 V at Site V and η_ORR ≈ 0.23 V at Site V) and favorable adsorption energetics, particularly on Si–N–related regions, indicating clear bifunctional photocatalytic potential. Collectively, SnSiGeN4 emerges as a stable, sustainable, high‑performance platform for UV‑visible light‑driven water splitting, with strong theoretical support for experimental validation and potential for scalable, noble‑metal‑free catalysis.

Abstract

The development of efficient and cost-effective catalysts for clean energy conversion remains a central challenge in materials science. Although platinum serves as the benchmark catalyst, its scarcity and high cost hinder large-scale deployment. In this study, we propose a newly predicted SnSiGeN4 MXene-family monolayer as a promising candidate for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER). Using first-principles calculations, we systematically investigated its electronic, vibrational, and optical properties across multiple exchange-correlation functionals, including hybrid approaches, revealing a wide and tunable band gap. Simulated infrared and Raman spectra further confirm the dynamical stability and the presence of catalytically active sites. Guided by these findings, we studied photocatalytic reaction analyses that demonstrate that the computed overpotentials for OER, ORR, and HER are comparable to those of Pt-based catalysts and outperform Ir-based systems, positioning SnSiGeN4 as a sustainable, high-performance platform for next-generation UV-visible-light-driven photocatalysis.

Figures (11)

• Figure 1: Top and side views of the optimized SnSiGeN$_4$ monolayer. The structure belongs to the hexagonal lattice system with space group P1 (No. 1). Atoms are labelled, and red-colored lines represent the calculated bond lengths between adjacent atoms.
• Figure 2: Schematic Representation of Band Edge Allignment at different pH.
• Figure 3: Projected density of states (PDOS) and electronic band structures of SnSiGeN$_4$ monolayer calculated using different exchange--correlation functionals.
• Figure 4: (a) absorption coefficient, (b) Dielectric constant, (c) extinction function, (d) refractive index.
• Figure 5: Vibrational IR and Raman spectra of the SnSiGeN$_4$ monolayer calculated with B3LYP and GGA functionals. The numerical label denotes the respective frequency mode.