▎ 摘　　要

NOVELTY - Annealing temperature in controlling number of shell formation in N-doped multi-shelled ruthenium (Ru)-cobalt (Co)-cobalt tetraoxide graphene-coated nano-spheres involves synthesizing the metal-organic frameworks (MOFs) by the reaction with ruthenium nitrosyl nitrate, cobalt nitrate (as metal precursors) and trimesic acid with the presence of polyvinyl pyrrolidone (PVP), pre-optimizing the optimal amount of PVP to 1.30 g during the synthesis of metal-MOFs, taking trimesic acid and PVP in 40 mL mixture solution of water, isopropyl alcohol, and dimethylformamide (DMF) in the ratio of 1:1:1 (vol.) under vigorous stirring. USE - Method for annealing temperature in controlling number of shell formation in N-doped multi-shelled ruthenium-cobalt-cobalt tetraoxide graphene-coated nano-spheres. ADVANTAGE - The quintupled shell structured nanospheres have shown remarkable electrocatalytic performance during water splitting with highest current density at lowest over-potential value in HER and OER under acidic media, and similarly, electrocatalytic activity gradually diminishes with decrease in the shell numbers inside nano-spheres. DETAILED DESCRIPTION - Annealing temperature in controlling number of shell formation in N-doped multi-shelled ruthenium (Ru)-cobalt (Co)-cobalt tetraoxide graphene-coated nano-spheres involves synthesizing the metal-organic frameworks (MOFs) by the reaction with ruthenium nitrosyl nitrate, cobalt nitrate (as metal precursors) and trimesic acid with the presence of polyvinyl pyrrolidone (PVP), pre-optimizing the optimal amount of PVP to 1.30 g during the synthesis of metal-MOFs, taking trimesic acid and PVP in 40 mL mixture solution of water, isopropyl alcohol, and dimethylformamide (DMF) in the ratio of 1:1:1 (vol.) under vigorous stirring, keeping the solution in the sonication bath for 20 minutes (min), keeping the resultant solution inside a 100 mL Teflon (polytetrafluoroethylene) lined autoclave and maintaining the temperature at 130℃ for 14 hours, centrifuging the products for 30 min at 4500 revolutions per minute, washing with ethanol : water (1:1;v/v) at least for 4-5 times, drying the material in the oven for at 85℃ for 10 hours to obtain ruthenium (Ru)-cobalt tetraoxide (Co3O4) MOFs, heating the Ru-Co3O4/graphene powder with melamine in a furnace under nitrogen (N2) atmosphere at different annealing temperatures of 250℃, 310℃, 380℃, 450℃ and 530℃ at heating rate of 2℃/min with keeping for 2.5 hours at N2 atmosphere, producing nanospheres with shell numbers of 1, 2, 3, 4 and 5, during the carbonation treatment process in such a nitrogen rich atmosphere at elevated temperature, the doping of nitrogen in carbon is realized and melamine generate ammonia (NH3) gas, calcining the resulting powder in an air atmosphere at 250℃ with the heating rate of 2℃/min, and holding for 45 min to obtain the final N-incorporated Ru-Co3O4graphene nanospheres with various number of shells.