Highly efficient hydrogen storage of a Sc decorated biphenylene monolayer near ambient temperature: ab initio simulations

Abstract

The energy demands for the growing development of society need to be met with alternative and green fuels like hydrogen energy for a lasting and sustainable future. One essential component of the hydrogen economy is the efficiency of its storage. We have studied the hydrogen-storage capability of the recently synthesized Biphenylene (BPh) decorated with Sc using first-principles density functional theory (DFT) and ab initio molecular dynamics (AIMD) techniques. Scandium attaches to the BPh sheet strongly with a binding energy of −3.84 eV, and a single Sc atom decorated on BPh can absorb a maximum of five H₂ molecules resulting in a high gravimetric weight percentage of 11.07, which is significantly higher than the DoE's ultimate criterion (6.5 wt%). Using the van't Hoff equation, strongly and weakly attached hydrogens correspond to desorption temperatures of 200 K and 397 K with an average of 305 K. The high binding of Sc to BPh is due to charge donation of the 3d orbital of Sc to the 2p orbital of C. The interactions between absorbed H₂ and BPh + Sc are due to charge transfer from the 3d-orbital of Sc to the σ* bond of H₂ molecules and backdonation from the σ bond of H₂ to an empty 3d-orbital of Sc known as the Kubas type interaction. Furthermore, phonon and AIMD simulations confirm the stability of BPh + Sc, and the presence of an energy barrier confirms no probability of Sc–Sc clustering on BPh. So, the theoretically stable BPh + Sc showing a high gravimetric weight percentage with an average 305 K desorption temperature might be a potential candidate for solid-stage hydrogen devices.