In this work, uniform hierarchical mesoporous 3D-urchin-like Bi2S3@2D-nanosheet g-C3N4 was synthesized via a superficial hydrothermal method. The prepared pristine Bi2S3, g-C3N4, and 3D-Bi2S3@2D-g-C3N4 composite samples were extensively studied for their electrochemical performance and exhibited superior battery-type behaviors. The results highlight that the optimized 3D-Bi2S3@2D-g-C3N4 composite sample exhibits a high areal capacity of 41.53 μA h/cm2 at 1 mA/cm2 and a good rate capability of 62.77% along with a remarkable capacity retention of 94.86% after 5000 cycles. The improved performance can be attributed to the good beneficial features of the synergistic effect, mesoporous structure, and lower dissolution. It offers a higher specific surface area, enriches electroactive sites, increases electronic/ionic conductivities, and reduces the interfacial resistance. Furthermore, the solid-state symmetric supercapacitors (SSCs) were assembled by two similar electrodes of 3D-Bi2S3@2D-g-C3N4 sandwiched between the KOH and PVA gel electrolyte. The fabricated SSC device provides a high areal capacity of 25.40 μA h/cm2 at 1 mA/cm2. Furthermore, the SSC delivers a maximum power density of 1495 μW/cm2 and an energy density of 3.17 μW h/cm2 with a good cyclic retention of 83.84% after 7500 cycles. This work also demonstrates the practical applicability of realizing red-light-emitting diodes by interconnecting two SSCs in series.

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A carbonaceous adsorbent prepared from an indigenous waste by acid treatment was tested for its efficiency in removing chromium ion. The parameters studied include agitation time, initial chromium ion concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm) obtained from the Langmuir isotherm plots were 27.40, 26.06, 26.06 and 26.17 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 60°C. The temperature variation study showed that the chromium ion adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the chromium ion solutions. Almost 70% removal of chromium ion was observed at 60°C. The Langmuir and Freundlich isotherms obtained, positive ∆H0value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of chromium ion on PDC involves physisorption mechanism.