Available online xxxKeywords: Hydrogen storage Graphene oxide Interlayer space Functional group Reduce graphene oxide Structural characterization a b s t r a c t Hydrogen storage properties of the derivatives of graphene, graphene oxide/reducedgraphene oxide are studied in this paper. Modified Hummer's method was adopted for synthesis of graphene oxide (GO) and reduced-graphene oxide (rGO). The morphology of GO/rGO was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of C]O and eOH group in the Fourier transform infrared (FTIR) spectrum and G-mode and 2D-mode in the micro-Raman studies confirmed the synthesis of the GO and rGO. Furthermore, the structural investigations using powder x-ray diffraction (XRD) reveals the hexagonal crystallographic phase of GO/rGO. The hydrogenstorage capacity of the GO/rGO sample is measured using indigenously fabricated high pressure hydrogen storage Sieverts' type volumetric setup at room temperature and pressure up to 80 bars. In present experimental investigations, GO was found to exhibit better H 2 uptake capacity (1.90wt.%) as compared to rGO (1.34 wt.%) at room temperature. It can be said that the oxygen functional groups work as spacers in between the graphene layers and increase the inter-layer space which in turn accumulate more number of hydrogen molecules on surface of carbon nano-sheets.

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Electrolyzers for CO2 reduction containing bipolar membranes (BPM) are promising due to low loss of CO2 as carbonates and low product crossover, but improvements in product selectivity, stability, and cell voltage are required. In particular, direct contact with the acidic cation exchange layer leads to high levels of H2 evolution with many common cathode catalysts. Here, Co phthalocyanine (CoPc) is reported as a suitable catalyst for a zero‐gap BPM device, reaching 53% Faradaic efficiency to CO at 100 mA cm−2 using only pure water and CO2 as the input feeds. It is also shown that the cell voltage can be lowered by constructing a customized BPM using TiO2 water dissociation catalyst, however this is at the cost of decreased selectivity. Switching the pure‐water anolyte to KOH improved both the cell voltage and CO selectivity (62% at 200 mA cm−2), but cation crossover could cause complications. The results demonstrate viable strategies for improving a BPM CO2 electrolyzer toward practical‐scale CO2‐to‐chemicals conversion.