Preparation and capacitive properties of a free-standing phosphomolybdic acid heteropoly blue modified reduced graphite oxide composite

Abstract

Polyoxometalates (POMs) have shown great potential for electrochemical energy storage. Herein, a phosphomolybdic acid heteropoly blue-modified reduced graphite oxide (PAHB/RGO) self-supporting composite is prepared through one-pot hydrothermal treatment. The individual PAHB molecule is adsorbed and evenly distributed on the RGO sheets through charge transfer. The specific capacitance of the PAHB/RGO composite is 395 F g⁻¹ at 1 A g⁻¹ as a binder-free electrode. Further kinetic analysis discloses that electrical double-layer capacitance dominates the total specific capacitance of the PAHB/RGO composite. An excellent capacity retention of 84% is obtained for the PAHB-9/RGO electrode after 5000 consecutive cycles at 5 A g⁻¹. A solid symmetrical supercapacitor (PAHB-9/RGO//PAHB-9/RGO) with a working voltage of 1.2 V has been assembled. The PAHB-9/RGO//PAHB-9/RGO cell can supply a high specific energy of 26.2 W h kg⁻¹ at 600 W kg⁻¹. A moderate capacity retention of 74%, moreover, is obtained after 10 000 consecutive charge–discharge at 5 A g⁻¹ for the PAHB-9/RGO//PAHB-9/RGO cell. This work provides insights into constructing excellent electrode materials based on POMs for supercapacitors.