XPS Analysis of Fe_xNi_yPS₃ vdW Materials Used in the Hydrogen Evolution Processes

In response to the global demand for sustainable energy solutions, the quest for stable and cost-effective hydrogen production has garnered significant attention in recent decades. Here, the emergence of layered metal phosphorus trichalcogenides (MPX₃, M: transition metal, X: chalcogen) materials and their two-dimensional counterparts with customizable composition and electronic structure holds great promise for such purposes. In the present study, we successfully synthesized large-scale and high-quality FePS₃, NiPS₃, and an alloyed counterpart, Fe_0.5Ni_0.5PS₃. Subsequent systematic investigations were conducted to probe their respective electronic structures and assess their hydrogen evolution reaction (HER) properties. Remarkably, our results unveiled the successful modulation of the bandgap for Fe_xNi_yPS₃, ultimately bestowing it with the most favorable HER performance for Fe_0.5Ni_0.5PS₃ when compared to the other two samples. Furthermore, our exploration into the evolution of the X-ray photoelectron spectroscopy (XPS) spectra demonstrated that the charge conversions of metal cations play a pivotal role in the HER reactions. This critical insight further enriches our understanding of the fundamental mechanisms governing the performance of the prepared layered MPX₃-based electrocatalysts, thus facilitating a comprehensive and detailed analysis of the pre- and post-HER reactions. This work not only sheds light on the intricate interplay between composition, electronic structure, and catalytic performance in the realm of novel electrocatalysts, but also contributes to the broader scientific community's pursuit of sustainable and efficient hydrogen production.