A feasible strategy of coating CoMoO4 on Co11(HPO3)8(OH)6 nanorods for improved practical application in supercapacitors

Abstract

Cobalt hydrogen phosphate hydroxides are potential electrode materials for supercapacitors due to their various oxidation states and morphologies. However, their electrochemical performance and practical application are limited by the poor cycling stability during long charge/discharge cycles. To address this drawback, Co₁₁(HPO₃)₈(OH)₆ nanorods (CHPO NRs) are covered by CoMoO₄ (CMO) with different microstructures using hydrothermal and reflux processes, respectively. The results indicate that the electrochemical performance of as-prepared CHPO@CMO is much better than that of individual CHPO and CMO. The specific capacities of CHPO@CMO obtained by hydrothermal and reflux processes are 495.1 and 837.1 C g⁻¹ at 1 A g⁻¹, respectively. More importantly, the electrochemical cycling performance of CHPO@CMO is significantly improved. In addition, a CHPO@CMO//AC hybrid device is assembled, and it shows improved electrochemical performance and good practical application, which come from the synergetic effect and high cycling stability of the covering CMO. The specific energies of the assembled devices are 23.8 W h kg⁻¹ at the specific power of 849.9 W kg⁻¹ (hydrothermal method) and 38.4 W h kg⁻¹ at the specific power of 850.7 W kg⁻¹ (reflux method). Thus, the strategy mentioned in this work gives the opportunity to improve the practical application of cobalt hydrogen phosphate hydroxides and other phosphates in energy conversion and storage, such as Co₃(PO₄)₂, Co₂(OH)PO₄ and Co₃P₂O₈.