Hierarchically Hybrid Porous Co 3 O 4 @NiMoO 4 /CoMoO 4 Heterostructures for High-Performance Electrochemical Energy Storage.

Hierarchical, ultrathin, and porous NiMoO 4 @CoMoO 4 on Co 3 O 4 hollow bones were successfully designed and synthesized by a hydrothermal route from the Co-precursor, followed by a KOH (potassium hydroxide) activation process. The hydrothermally synthesized Co 3 O 4 nanowires act as the scaffold for anchoring the NiMoO 4 @CoMoO 4 units but also show more compatibility with NiMoO 4 , leading to high conductivity in the heterojunction. The intriguing morphological features endow the hierarchical Co 3 O 4 @NiMoO 4 @CoMoO 4 better electrochemical performance where the capacity of the Co 3 O 4 @NiMoO 4 @CoMoO 4 heterojunction being 272 mA·h·g -1 at 1 A·g -1 can be achieved with a superior retention of 84.5% over 1000 cycles. The enhanced utilization of single/few NiMoO 4 @CoMoO 4 shell layers on the Co 3 O 4 core make it easy to accept extra electrons, enhancing the adsorption of OH - at the shell surface, which contribute to the high capacity. In our work, an asymmetric supercapacitor utilizing the optimized Co 3 O 4 @NiMoO 4 @CoMoO 4 activated carbon (AC) as electrode materials was assembled, namely, Co 3 O 4 @NiMoO 4 @CoMoO 4 //AC device, yielding a maximum high energy density of 53.9 W·h·kg -1 at 1000 W·kg -1 . It can retain 25.92 W·h·kg -1 even at 8100 W·kg -1 , revealing its potential and viability for applications. The good power densities are ascribed to the porous feature from the robust architecture with recreated abundant mesopores on the composite, which assure improved conductivity and enhanced diffusion of OH - and also the electron transport. The work demonstrated here holds great promise for synthesizing other heterojunction materials M 3 O 4 @MMoO 4 @MMoO 4 (M = Fe, Ni, Sn, etc).