Researchers at Tokyo Institute of Technology, University of Tsukuba, and colleagues in Japan report a promising hydrogen carrier in the form of hydrogen boride nanosheets. The two-dimensional materials derived from magnesium diboride (MgB₂) were first reported by researchers in Japan in 2017.

The nanosheets exhibit extraordinary electronic and mechanical properties in addition to hydrogen storage capacity. This material, which has only recently begun to be explored, could go on to be used as safe, light-weight, high-capacity hydrogen storage materials.

Hydrogen boride nanosheets (HB sheets) release hydrogen under UV light. The hydrogen storage and release capacity of HB sheets is exceptionally high due to their two-dimensional nature and unique electronic band structure.

Innovative nanosheets made from equal parts of hydrogen and boron have a greater capacity to store and release hydrogen compared with conventional metal-based materials.

This finding reinforces the view that hydrogen boride nanosheets (HB sheets) could go beyond graphene as a nano-sized multifunctional material.

Their open-access study, published in Nature Communications, found that hydrogen can be released in significant amounts (up to 8 wt%) from HB sheets under ultraviolet light, even under mild conditions—that is, at ambient room temperature and pressure. This result indicates that the sheets have a high H₂-storage capacity compared with previously reported metal H₂-storage materials.

Such an easy-to-handle setup opens up possibilities for HB sheets to be utilized as highly efficient hydrogen carriers, which are expected to become increasingly in demand as a clean energy source in the coming decades.

When HB sheets emerged in 2017, scientists recognized they could become an exciting new material for energy, catalysis and environmental applications. The breakthrough research garnered plaudits for its creative approach to materials design. A review article published in Chem in 2018 hailed the successful realization of HB sheets as “an exquisite example of human ingenuity at the pinnacle of innovative synthetic chemistry.”

HB sheets are expected to be applied for light-weight, light-responsive, and safe hydrogen carriers. Currently, HB sheets are only responsive to ultra-violet light, thus, the visible-light sensitivity is important for their industrial application.

Also, refilling of hydrogen remains a key challenge in developing sustainable, viable hydrogen storage solutions. To address this issue, the team is investigating the visible-light sensitivity, rechargeability, and long-term durability of HB sheets. Cost reduction of the starting materials—magnesium diboride—will be another important factor.

The cross-institutional study also showcases the predictive power of first-principles calculations in materials science as a way of investigating the mechanism of hydrogen release.

Resources

• Reiya Kawamura, Nguyen Thanh Cuong, Takeshi Fujita, Ryota Ishibiki, Toru Hirabayashi, Akira Yamaguchi, Iwao Matsuda, Susumu Okada, Takahiro Kondo and Masahiro Miyauchi (2019) “Photoinduced hydrogen release from hydrogen boride sheets.” Nature Communications doi: 10.1038/s41467-019-12903-1