Photoinduced hydrogen release from hydrogen boride sheets

Reiya Kawamura,Susumu Okada,Akira Yamaguchi,Iwao Matsuda,Masahiro Miyauchi,Takahiro Kondo,Takeshi Fujita,Toru Hirabayashi,Ryota Ishibiki,Nguyen Thanh Cuong

doi:10.1038/s41467-019-12903-1

Reiya Kawamura, Susumu Okada + Show 8 more

Open Access

https://doi.org/10.1038/s41467-019-12903-1

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Abstract

Hydrogen boride nanosheets (HB sheets) are facilely synthesized via ion-exchange treatment on magnesium diboride (MgB2) in an acetonitrile solution. Optical absorption and fluorescence spectra of HB sheets indicate that their bandgap energy is 2.8 eV. According to first-principles calculations, optical absorption seen at 2.8 eV is assigned to the electron transition between the σ-bonding states of B and H orbitals. In addition, density functional theory (DFT) calculations suggest the other allowed transition from the σ-bonding state of B and H orbitals to the antibonding state with the gap of 3.8 eV. Significant gaseous H2 release is found to occur only under photoirradiation, which causes the electron transition from the σ-bonding state to the antibonding state even under mild ambient conditions. The amount of H2 released from the irradiated HB sheets is estimated to be 8 wt%, indicating that the sheets have a high H2-storage capacity compared with previously reported metal H2-storage materials.

Highlights

Hydrogen boride nanosheets (HB sheets) are facilely synthesized via ion-exchange treatment on magnesium diboride (MgB2) in an acetonitrile solution
We calculated the electronic structure of the HB sheets using density functional theory (DFT) and investigated their optical properties to examine the relationship between the electronic structure and the H2-release property
The HB sheets were synthesized via a wet chemical exfoliation method

Summary

Introduction

Hydrogen boride nanosheets (HB sheets) are facilely synthesized via ion-exchange treatment on magnesium diboride (MgB2) in an acetonitrile solution. Significant gaseous H2 release is found to occur only under photoirradiation, which causes the electron transition from the σ-bonding state to the antibonding state even under mild ambient conditions. Among the various candidates as a new class of 2D nanosheets beyond graphene[6], borophene, which is composed of B atoms arranged in a single monoatomic layer, was theoretically predicted to have unique mechanical and electronic properties[7] and was successfully synthesized on Ag (111) under ultrahigh-vacuum conditions[8]. Our group established the synthesis of the hydrogen boride nanosheets (HB sheets) with a well-defined chemical composition using a facile ion-exchange technique in an organic solvent through an exfoliation process[15]. We calculated the electronic structure of the HB sheets using density functional theory (DFT) and investigated their optical properties to examine the relationship between the electronic structure and the H2-release property

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