Rational design of 2D Xene-based (Photo)Electrocatalysts with built-in iron-triad bimetallic nanoalloys for efficient overall water splitting

2D Xenes, a family of monoelemental 2D materials analogous to graphene, are emerging as promising platforms for next-generation (photo)electrocatalysts owing to their high surface-to-volume ratio and unique (opto)electronic properties. Nevertheless, their practical deployment in energy conversion remains largely unexplored. Herein, we provide a rational design strategy for advanced 2D Xene-based (photo)electrocatalysts by integrating iron-triad bimetallic nanoalloys (i.e., NiFe, NiCo, and CoFe) via electrochemical deposition. As a proof of principle, germanane (2D–GeH) is employed as a model 2D Xene to assess performance toward (photo)electrocatalytic overall water splitting (OWS). After accurate material and device characterization, the NiCo@GeH heterostructure delivers optimal bifunctional activity under alkaline conditions (1 M KOH), reaching 100 mA cm −2 at 1.95 V and 1.89 V under electrocatalytic and photoelectrocatalytic conditions, respectively. Mechanistic analysis identifies H 2 O dissociation as the rate-determining step during the hydrogen evolution reaction, while density functional theory calculations reveal the favorable role of NiCo@GeH in promoting H 2 O dissociation. Overall, these findings point out the potential of 0D/2D heterostructures made of 2D Xenes carrying iron-triad bimetallic nanoalloys as efficient (photo)electrocatalysts for OWS.