Electrochemical hydrogen-storage capacity of graphene can achieve a carbon-hydrogen atomic ratio of 1:1

• Published in: Science China. Chemistry 2022-02, Vol.65 (2), p.318-321
• Main Authors: He, Quanfeng, Zeng, Lanping, Han, Lianhuan, Peng, Juan, Sartin, Matthew M., Tan, Yuan-Zhi, Zhan, Dongping, Tian, Zhong-Qun
• Format: Article
• Language: English
• Subjects: Adatoms; Anodic stripping; Carbon; Catalytic converters; Chemical vapor deposition; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Communications; Electrodes; Foils; Graphene; Hydrogen; Hydrogen storage materials; Storage capacity; Surface diffusion
• ISSN: 1674-7291; 1869-1870
• DOI: 10.1007/s11426-021-1127-1

As a promising hydrogen-storage material, graphene is expected to have a theoretical capacity of 7.7 wt%, which means a carbon-hydrogen atomic ratio of 1:1. However, it hasn’t been demonstrated yet by experiment, and the aim of the U.S. Department of Energy is to achieve 5.5 wt% in 2025. We designed a spatially-confined electrochemical system and found the storage capacity of hydrogen adatoms on single layer graphene (SLG) is as high as 7.3 wt%, which indicates a carbon-hydrogen atomic ratio of 1:1 by considering the sp3 defects of SLG. First, SLG was deposited on a large-area polycrystalline platinum (Pt) foil by chemical vapor deposition (CVD); then, a micropipette with reference electrode, counter electrode and electrolyte solution inside was impacted on the SLG/Pt foil (the working electrode) to construct spatially-confined electrochemical system. The SLG-uncovered Pt atoms act as the catalytic sites to convert protons (H + ) to hydrogen adatoms (H ad ), which then spill over and are chemically adsorbed on SLG through surface diffusion during the cathodic scan. Because the electrode processes are reversible, the H ad amount can be measured by the anodic stripping charge. This is the first experimental evidence for the theoretically expected hydrogen-storage capacity on graphene at ambient environment, especially by using H + rather than hydrogen gas (H 2 ) as hydrogen source, which is of significance for the practical utilization of hydrogen energy.