The work reported here deals with the development of an efficient non-platinum electrocatalyst for electrochemical oxygen reduction reaction (ORR) through a sequential pathway involving hydrothermal treatment followed by freeze-drying to build the desired structural architecture of the catalyst. The designed catalyst (Co 3 O 4 / nitrogen-doped entangled porous 3D graphene (NEGF)), which contains Co 3 O 4 nanorods anchored on the surface of three-dimensional (3D)-structured N-doped graphene, was found to display higher ORR activity during single-electrode testing and demonstrate a Zn−air battery (ZAB) system. Under the hydrothermal treatment at 180 °C, in the presence of ammonia, nitrogen was doped into the carbon framework of graphene, which subsequently formed a self-assembled entangled 3D structure of graphene after freeze-drying. The hydrothermal treatment and freeze-drying processes were found to play vital roles in tuning the morphological and structural features of the catalyst. The doped nitrogen, apart from its favorable contribution toward ORR, helped facilitate efficient dispersion of oxide nanorods on graphene. Co 3 O 4 /NEGF displayed remarkable ORR activity in 0.1 M KOH solution, as evident from the 60 mV onset potential shift compared to the state-of-the-art Pt/C catalyst and the Tafel slope value of 74 mV dec −1 vs 68 mV dec −1 for Pt/C. The ZAB fabricated by employing Co 3 O 4 /NEGF as the cathode catalyst was found to be an efficient competitor for the system based on the Pt/C cathode. This high performance has been credited to the controlled interplay of the governing factors such as the interfacial interactions leading to the efficient dispersion of metal oxide nanorods, increased catalyst surface area, the cooperative effect arising from the defects present in the N-doped porous 3D graphene, and the synergetic interactions operating in the system.

Currently, the low energy efficiency of water electrolysis has compelled research toward the development of novel and energy‐effective strategies for low‐cost H2 generation. In this context, we report a new concept of simultaneous H2 and electricity generation by separating out the exothermic self‐sustained Al−H2O reaction via electrochemistry. In addition, to catalyze the cathodic water reduction reaction, a single‐pot and environmentally benign synthesis method is adopted. It results in the design of an electrocatalyst composed of Co@CoAl‐layered double hydroxide core‐shell nanospheres anchored over in situ generated N‐doped graphene. Toward the water reduction reaction, the designed catalyst shows a negative voltage shift of mere around 113 mV with respect to the commercial Pt/C catalyst to reach the benchmark 10 mA cm−2, with excellent stability of approximately 86 % voltage retention after 12 h of continuous operation. The catalytic superiority of our material is evident when taken for battery‐level testing; the fabricated device was able to deliver an average output voltage of around 0.95 V at a discharge current density of 5 mA cm−2 along with H2 liberation, which was also detected and quantified through gas chromatography.

Both mechanically and electrically rechargeable zinc-air batteries (ZAB) have received much interest due to their high energy density and suitability for mobile and stationary applications. However, their commercialization has been...