Hydroxyl-decorated graphene systems as candidates for organic metal-free ferroelectrics, multiferroics, and high-performance proton battery cathode materials

Using a first-principles method we show that graphene based materials, functionalized with hydroxyl groups, constitute a class of multifunctional, lightweight, and nontoxic organic materials with functional properties such as ferroelectricity, multiferroicity, and can be used as proton battery cathode materials. For example, the polarizations of semihydroxylized graphane and graphone, as well as fully hydroxylized graphane, are much higher than any organic ferroelectric materials known to date. Further, hydroxylized graphene nanoribbons with proton vacancies at the end can have much larger dipole moments. They may also be applied as high-capacity cathode materials with a specific capacity that is six times larger than lead-acid batteries and five times that of lithium-ion batteries.

Figure 1

(a) Side view of graphane and SHLGA, (b) different orientations of the hydroxyl group in SHLGA, (c) top view of SHLGA with different polarization orientations, and (d) side view of graphone and HLGO. Gray, white, and red spheres denote C, H, and O atoms, respectively.

Figure 2

(a) Side view of single-layer HLGA, (b) multilayer HLGA, and (c) top view of multilayer HLGs.

Figure 3

(a) Hydroxylized zigzag edge of ZGNR; (b) bulk crystal of ZGNRs decorated with –OH; ZGNR decorated with –OH with (c) two proton vacancies and (d) $N$ proton vacancies at every edge.

Figure 4

Intercalation and deintercalation of cathode materials based on (a) HLGA and (b) ZGNR decorated with –OH.