Resonance loss due to the polarization accumulation effect induced by phosphorus vacancies for enhancing electromagnetic wave absorption

Vacancy engineering is an effective approach to modulate the electronic structures of materials. However, the contribution of phosphorus vacancies to microwave absorption (MA) has not been clearly described. In this work, CoP nano-cubes with phosphorus vacancies (Pv-CoP@C) were successfully prepared, and the effect of phosphorus vacancies on MA was investigated for the first time. Benefiting from the resonance absorption induced by the polarization accumulation effect from phosphorus vacancies, we found a clear correlation between phosphorus vacancies and the low-frequency shift of impedance adaptation (IA). Specifically, the presence of phosphorus vacancies caused resonance loss, making the IA region move 7.0 GHz towards low frequency. Furthermore, the phosphorus vacancies not only introduced more polarization centers, but also caused the gradual delocalization of bound electrons around the Co-P bond, resulting in excellent MA performance of Pv-CoP@C. Therefore, the minimum reflection loss (RLmin) was increased from -36.9 dB (CoP@C) to -51.8 dB (Pv40-CoP@C). Meanwhile, the position of the Rlmin peak shifted from 17.4 GHz for CoP@C to 14.0 GHz for Pv60-CoP@C. This work establishes the correlation between the phosphorus vacancies and MA, which provides a new insight for the design and application of vacancy engineering in the field of MA. CoP nano-cubes with phosphorus vacancies were successfully synthesized, and the phosphorus vacancies make the impedance adaptation region move to low frequency. The great impedance matching and loss capacitance resulted in excellent MA performance.