Partially reduced holey graphene oxide for high performance capacitive deionization

•A novel method for the preparation of partially reduced holey graphene oxide is proposed.•The partially remaining oxygen-containing functional groups can prevent π-π stacking phenomenon in graphene sheets.•The electrode delivers a high desalination capacity and good cycling performance.•The rational combination of surface etching and partial reduction can applied to other energy storage systems. Capacitive deionization (CDI) is a technology with excellent potential for applications in the field of desalination and water treatment. Graphene is considered to be an ideal material in the field of CDI due to its large surface area and high electrical conductivity. However, the severe π-π restacking of graphene sheets leads to problems such as long ion transport distances and small interlayer distances, which result in low desalination capacity and poor cycling performance. Herein, we prepared partially reduced holey graphene oxide by H2O2 treatment and subsequent ascorbic acid reduction of graphene oxide, which led to high specific capacitance and cyclic stability. The partially remaining oxygen-containing functional groups can act as spacers to effectively prevent π-π stacking phenomenon from occurring in graphene sheets, which provides sufficient storage space to facilitate the rapid transfer of ions. As electrode material for CDI, the electrode delivers a desalination capacity as high as 22.4 mg g−1 (applied potential: 1.4 V; initial NaCl concentration: 1500 ppm) and good cycling performance (desalination capacity retention of 81.5 % after 50 cycles). This rational combination of surface etching and partial reduction strategies can be used to fabricate high-performance CDI electrodes, which are expected to be applied to other energy storage and conversion systems.