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The development of high-efficiency and durable bifunctional electrocatalysts is an important and challenging topic in the area of energy storage/conversion. Herein, we prepared metallic cobalt nanoparticle decorated N-doped graphitic sheets (Co@NGr) by adopting facile pyrolysis of a mixed ligand cobalt-based MOF (CoMOF-2) as a sacrificial template displaying good OER and HER activity. The catalytic material harvested at three different pyrolytic temperatures was characterized by various analytical methods such as PXRD, SEM, TEM, Raman, and XPS analyses. The catalytic activity of the obtained hybrid composite materials towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was studied. Co@NGr-900 was found to be an efficient bifunctional electrocatalyst and 10 mA cm−2 current density was afforded at an overpotential of 390 mV for OER and 340 mV for HER respectively. This study provides insight for the development of cost-effective nonprecious element-based electrocatalysts for water splitting which has relevance in energy storage and conversion. Catalytic performance is governed by the synergistic compositional effect of metallic cobalt/nitrogen-doping in the graphitic carbon increasing the electrical conductivity/active sites of the composite material.

The controlled formation of porous ZnO microtubes via the formation of tubular hydrozincite under ambient conditions from bulk ZnO followed by calcination at 500 °C for 2 h is presented. The tubular structure is a hierarchical assembly of ZnO flowers to form uniform tubes, with ∼30 μm length, ∼2 to 7 μm width and ∼400 to 500 nm wall thickness, where the flowers are made of 3D assembled porous ZnO flakes. The surface area of the tubular ZnO structure is quite good (58 m2 g−1). The developed synthetic procedure is quite flexible, and we have also synthesized nanostructured ZnO of varying morphologies from bulk ZnO just by changing the synthetic conditions. The developed ZnO microtubes showed excellent microstructure-based sensing and catalytic properties. A novel biosensor based on the synthesized porous tubular ZnO exhibited high sensitivity (54.5 mA M−1 cm−2) and low LOD (limit of detection, 0.2 mM (S/N = 3)) of cholesterol at room temperature, superior to that of sensors made of other porous ZnO shapes synthesized by varying the conditions, as well as other sensors reported in the literature. It is superior even in comparison with a nano gold modified sensor. The tubular ZnO structure also showed superior catalytic activity (92%) for the synthesis of 5-benzyl-1H-tetrazole to that of other reported solid catalysts. Thus, it is expected that the developed porous tubular ZnO should find potential industrial application in the sensor as well as the catalysis field. Moreover, the synthesis from bulk ZnO makes the procedure cost effective.