Branched Alkylamine–Reduced Graphene Oxide Hybrids as a Dual Proton–Electron Conductor and Organic-Only Water-Splitting Photocatalyst

Abstract

We report multifunctionalities including the solid electrolytic property, electron conductivity (EnC), and photocatalytic water splitting (PWS) ability of organic-only hybrids obtained by intercalating short and branched-chain alkylamines including methylamine (MA), butylamine (BA), pentylamine (PA), and isomethylbytylamine (IMBA) in reduced graphene oxide (rGO). The alkylamine-rGO hybrids were synthesized by a facile solid-state reduction process. Within the series, IMBA-rGO exhibited high proton conductivity (PrC), EnC, and optimized PWS capacity. The PrC of IMBA-rGO was from 10^-4 to 10^-3 S cm^-1, which is only half an order less than that for pristine GO. The EnC was 1.25 μA/V. Though the PWS performances of MA-rGO, BA-rGO, and PA-rGO were comparatively lower, IMBA-rGO could generate about 1.5 times H₂ compared with that for R-TiO₂. The IR spectra indicate the association of IMBA and GO by chemical bonds. The Raman spectra show the transformation of GO's nonconductive sp³ carbon sites into electron-conductive sp² carbon centers. The thermogravimetric analysis show improved water adsorbing capacity of IMBA-rGO, which resulted in higher PrC. Doping of the nitrogen atom at the graphitic sp² system was confirmed from the presence of pyrrolic N in X-ray photoelectron spectroscopy spectra. The resultant N-type semiconducting behavior is majorly responsible for the PWS process. The powder X-ray diffraction analysis indicates a more flexible interlayer space in IMBA-rGO, which facilitates both the reformation of hydrogen bonds during proton conduction and water dynamics during photocatalysis. The material indicates the possibility of devising graphene-based organic-only multifunctional hybrids.