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

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.