Insight of S, N co-doped graphene aerogel (double reduction)/cobalt (Ⅱ)-substituted α-Keggin-type polyoxometalate nanocomposites with synergistically enhanced impedance matching and energy conservation performance

Abstract

Exploring new types of absorbing materials has always been the focus and hot spot of stealth research. As we all know, the best conductivity of absorbing materials is generally in the range of semiconductor. Polyoxometalate is a kind of metal oxygen cluster with semiconductor properties and a good electron acceptor, but there is little research on its absorption property. In this work, we synthesized S, N co-doped graphene aerogel (secondary reduction by ascorbic acid)/cobalt (Ⅱ)-substituted α-Keggin-type polyoxometalate (SNGA(Vc)/α-SiW11Co) nanocomposites through some facile routes. The graphene aerogel and polyoxometalate could analogously play the role of alkali and acid, respectively, attracting each other through electrostatic interaction, in addition to hydrogen bonding (N–H- … O, O–H- … O). By changing the types of element doped graphene aerogels and reduction degree, it could regulate the conductivity and affect the polarization relaxation capacity of SNGA(Vc)/α-SiW11Co nanocomposites. With a filling rate of 1:2.5 in paraffin matrix, the maximum reflection loss was up to −67.9 dB at 17.3 GHz and 1.6 mm. There was also another strong absorption peak value of −63.7 dB at 3.5 mm and 6.9 GHz. The absorption bandwidths with the RL value lower than −10 and −20 dB remarkably reached as strong as 14.1 and 13.4 GHz when the thickness range was 1.5–5 mm, respectively, meaning the super electromagnetic wave absorption ability of SNGA(Vc)/α-SiW11Co nanocomposites. This study demonstrates that the polyoxometalate composite materials can become a novel idea for designing high-efficiency electromagnetic wave absorbers.