Unique 2D TMXTe monolayers (TM = Ti, Zr, Hf; X = Si, Ge) as high-efficiency electrocatalysts for the oxygen reduction reaction: a theoretical study

Abstract

Developing cost-effective electrocatalysts for the oxygen reduction reaction (ORR) is critical for advancing hydrogen fuel cells. This study systematically investigates, via density functional theory (DFT), a promising class of ORR electrocatalysts based on unique two-dimensional TMXTe monolayers (TM = Ti, Zr, Hf; X = Si, Ge) with a sandwich-like configuration. Our findings reveal that the ZrSiTe monolayer, featuring the surface-exposed ZrTe motif that is regarded as a structural analogue of the superatomic unit ZrO known for its Pd-like behavior, can effectively activate adsorbed O₂ molecules and exhibit exceptional ORR catalytic activity. The calculated overpotential (η) is as low as 0.21 V for the dissociation pathway and 0.46 V for the association pathway, rivaling or even surpassing the state-of-the-art Pt catalyst. Furthermore, analogous monolayers including TiSiTe, HfSiTe, and ZrGeTe, which possess similar distinctive TMTe motifs (TM = Ti, Zr and Hf), also demonstrate outstanding ORR activity with low overpotentials in the range of 0.38–0.46 V. In addition to their superior catalytic efficiency, these monolayers exhibit high selectivity, high stability, and favorable electrical conductivity. The underlying catalytic mechanism is elucidated in detail. This work can offer not only a series of highly promising ORR catalyst candidates but also novel insights for designing low-cost and high-performance alternatives to precious metal-based catalysts for fuel cell applications.