A very small amount (0.1 wt%) of Co(OH)2 nanoplates enhances triboelectric performance of polymers†

Hexagonal Co(OH)₂ nanoplates with a diameter of 1.28 ± 0.08 μm and a thickness of 52 ± 14 nm were prepared, showing facile generation of static electricity in a plastic container. Based on this observation, Co(OH)₂ nanoplates were incorporated into polymer matrixes such as polyvinylpyrrolidone (PVP) and polyurethane (PU). The resultant PVP–Co(OH)₂ (PVP–Co) and PU–Co(OH)₂ (PU–Co) films bearing an optimal amount (0.1 wt%) of Co(OH)₂ nanoplates showed dramatically-enhanced triboelectric performance, compared with pristine polymer films. While PVP and PU films exhibited output peak-to-peak voltages (V_p–p) of 249 and 423 V and output peak-to-peak currents (I_p–p) of 23 and 60 μA, respectively, with a pushing force of 2 kg f, the PVP–Co0.1 and PU–Co0.1 films showed V_p–p of 407 and 612 V with I_p–p of 41 and 85 μA, respectively. Triboelectric devices fabricated with PVP–Co0.1 and PU–Co0.1 films showed the maximum power densities of 0.38 and 1.22 mW cm⁻², respectively, and worked as power sources to charge a capacitor and to operate LEDs and a calculator. We suggest that the enhanced triboelectric performance of PVP–Co0.1 and PU–Co0.1 is attributable to the facile oxidation of Co²⁺ to Co³⁺ in Co(OH)₂ nanoplates.