A facile and effective one‐step in‐situ technique for the synthesis of layered two‐dimensional metallic vanadium sulfide‐reduced graphene oxide (VS2/rGO) nanocomposite (NComp) hasbeen described and their electrocatalytic properties towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been studied. From transmission and scanning electron microscopy analyses, it was observed that the layered two‐dimensional VS2 nanoparticles successfully grew over the layered graphene matrix. The as‐synthesized NComp displayed excellent electrocatalytic activities towards ORR with a four‐electron transfer pathway, and OER in alkaline medium. The synthesized nanocatalyst exhibits lower ΔE value (0.75 V) as compared to other literature values, high catalytic current density (−6.26 mA cm−2 for ORR) with a lower Tafel slope (59 mV dec−1), as compared to Pt/C, and lower overpotential (η=0.31 V at 10 mA cm−2 for OER) with a smaller Tafel slope (68 mV dec−1) than those of RuO2. Moreover, it displays high electrochemically active surface area, long‐term stability in alkaline medium and good resistance to the methanol crossover effect. The enhanced bifunctional electrocatalytic properties of the synthesized nanocatalyst may be owing to the synergistic effect of combining VS2 and rGO, which improves the surface area, adsorption of reaction intermediates, active sites density, and electrical conductivity. Along with the high stability of the hybrid NComp, these advantages provide immense promise for triggering breakthroughs in fuel‐cell electrocatalysis.

Exploring a sustainable, cost-effective, and efficient bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is very significant as well as challenging to develop an energy conversion–storage system. Herein, we demonstrate a fabrication technique of an organic–inorganic hybrid polypyrrole (ppy)/AgVO3, and its surface was further modified by porphrin (porphy) to boost its catalytic performances. The C,N-based ppy/AgVO3/porphy nanocatalyst acts as a charge transport highway to accelerate the sluggish OER/ORR kinetics and results in its impressive bifunctional performances. It exhibits an outstanding four-electron ORR activity with higher onset potential (1.03 V) and remarkable OER catalytic performance carrying a lowest overpotential (η10) of 220 mV, largely outperformingAgVO3 and ppy/AgVO3. Initially the very low ORR/OER activities of AgVO3 nanorods come from poor O2 and OH– adsorption on V5+ sites due to its extremely low electrochemical active surface area (ECSA) and poor electrical conductivity. The ppy loading has improved its catalytic performances by providing new active sites due to the presence of pyrrolic-N. Finally, the active site density was greatly enhanced after porphy loading over ppy/AgVO3, as porphy offers additional pyridinic-N along with pyrrolic-N atom. Furthermore, developed mesoporous surface after porpy incorporation provides high electrical conductivity, large surface area, enhanced charge–mass transport, close electrolyte–catalyst contact, and improved stability. Considering its bifunctional activity, NComp has been further evaluated by integrating it into a prototype zinc–air battery (ZAB), where a low discharge–charge voltage gap (0.71 V at 10 mA·cm–2) and a large peak power density (301 mW·cm–2) were achieved. Moreover, the NComp-based rechargeable ZAB (RZAB) is efficient enough to be operated evenly for 100 discharge–charge cycles. Most importantly, our findings may offer a powerful yet easy fabrication method of corrosion resistant high-performance catalyst through regulating active sites for investigating catalysis.

The adverse effects of the advancement of civilization have upset the environment significantly by heavy metal ion toxicity, empoisoning of soil, water, food, etc. In this work, Ag loaded metal...

In this study, a novel organic−inorganic polyaniline/ silver/silver molybdate (PANI/Ag/Ag 2 MoO 4 ) heterojunction nanocatalyst has been fabricated by in situ depositing Ag 2 MoO 4 on p-type PANI to explore two different catalytic properties, e.g., photocatalytic degradation of antibiotic ciprofloxacin (CIP) and electrocatalytic reduction of oxygen. After hybridization of Ag 2 MoO 4 with PANI, the p-n heterojunction developed and consequently z-scheme induced efficient photogenerated charge carrier separation and migration occur due to the internal electric field developed at the heterojunction interface. Compared with pure Ag 2 MoO 4 , the heterojunction nanocomposite possessed significantly enhanced photocatalytic activity as evidenced by the degradation of Congo Red (CR) dye under UV light irradiation. The optimum composite with 20 wt % PANI nanorods exhibited paramount photocatalytic activity over all the composites. Subsequently, 99.99% of CIP removal was achieved with this optimal composite within 40 min. On the other hand, it displays admirable electrocatalytic activity toward oxygen reduction reaction (ORR) compared to Ag 2 MoO 4 with high ORR onset potential. It is worth mentioning that PANI was beneficial toward both improved photocatalytic and electrocatalytic activity. Our study provides a simple method to design and fabricate a semiconductor composite material with staggered band structure which exhibits enhanced photocatalytic and ORR performance.