Hierarchical Structure MnO 2 Coated PDMS−Carbon Nanotube Sponge as Flexible Electrode for Electrocatalytic Water Splitting and High Performance Supercapacitor

As a typical transition metal oxide, MnO 2 has great potential in catalysis and energy storage, but its poor conductivity greatly limits its performance. PDMS−carbon nanotube sponges have excellent electrical conductivity and flexibility. Herein, according to the principle of complementary, we propose a novel hierarchical PDMS−carbon nanotube sponge@MnO 2 electrode with uniform size and morphology. In view of the structural preponderances and multifunctional of the materials, the PDMS−carbon nanotube sponge@MnO 2 has been investigated as the binder−free electrode materials for both supercapacitors and electrocatalysis applications. PDMS−carbon nanotube sponge@MnO 2 electrode exhibits an admirable HER property with a low onset potential of 112 mV at −30 mA cm −2 , a minimal overpotential (η=258 mV), a small Tafel slope (71 mV dec −1 ), large anodic currents and stability for 20 h in 0.1 M H 2 SO 4 solution. Moreover, as supercapacitor electrode, the PDMS−carbon nanotube sponge@MnO 2 electrode achieves a specific mass capacitance reaching 124.7 mF cm −2 at 1 A cm −2 and good flexibility, which are better than those ternary transition metal oxides. The assembled asymmetric device with the PDMS−carbon nanotube sponge@MnO 2 and CNTs respectively as positive and negative electrode has a large window voltage of 1.4 V, and thus acquires an expected specific mass capacitance (422 mF cm −3 at the current density of 1 A cm −3 ) and an outstanding higher energy density of 15.3 W h kg −1 (at 371 W kg −1 ).