Controlling Photoinduced H2 Release from Freestanding Borophane Sheets Under UV Irradiation by Tuning B-H Bonds

Hydrogen boride (HB), a freestanding 2D hydrogenated-borophene (borophane) polymorph, is synthesized via ion exchange. HB sheets with a B/H atomic ratio of 1.0 are confirmed to contain three-center-two-electron B-H-B bonds and two-center-two-electron terminal B-H bonds. The optical properties of HB sheets are expected to be tunable by changing the BHB/BH bond ratio, which alters the electronic structure of HB sheets; however, this is not yet achieved. This study demonstrates that controlling the BHB/BH bond ratio in the HB sheets is possible without altering the hydrogen content by adjusting the volume of ion-exchange resin during synthesis, thus enabling the tuning of the photoinduced H-2 release under UV irradiation. Furthermore, the fluorescence intensity correlates with the absorbance ratio of the BHB and BH vibrational modes. Increasing the BHB/BH bond ratio enhances the luminescence intensity, whereas reducing it enhances the photoinduced H-2 release rate under UV irradiation. The ability to control the BHB/BH bond ratio of HB sheets provides new avenues for optimizing their properties for various applications, including hydrogen storage and photocatalysis.

Automated summary

Hydrogen boride (HB), a freestanding 2D hydrogenated-borophene (borophane) polymorph, is synthesized via ion exchange. Control of the BHB/BH bond ratio in HB sheets is achieved by adjusting the volume of ion-exchange resin during synthesis. The ability to control the BHB/BH bond ratio provides new avenues for optimizing the properties of HB sheets for various applications.