Preparation of β -Co(OH) 2 nanosheets for pseudocapacitive electrode via cathode glow discharge electrolysis

β -Co(OH) 2 nanosheets were prepared in NaNO 3 solution by cathode glow discharge electrolysis (CGDE) technique, in which Co sheet and Pt needle were regarded as anode and cathode, respectively. The formation mechanism of β -Co(OH) 2 was discussed in detail, and the electrochemical performance was investigated as an electrode material for the pseudocapacitor. The results showed that the obtained β -Co(OH) 2 has a single phase of the hexagonal brucite-like nanosheets with an angle of adjacent edges of 120°, side length of 400–500 nm, and thickness of 10-20 nm. The average pore size and specific surface area are 33.1 nm and 122.1 m 2 g −1 , respectively. The β -Co(OH) 2 nanosheets exhibit a high specific capacitance of 335 F g −1 and excellent capacity retention of 77.1% after 3000 charge-discharge cycles at 1 A g −1 . CGDE offers a simple, fast, highly effective, and green strategy for the preparation of β -Co(OH) 2 nanosheets. The prepared β -Co(OH) 2 nanosheets can be used as an alternative electrode material for supercapacitors. Graphical Abstract Hexagonal β -Co(OH) 2 nanosheets were prepared by cathode glow discharge electrolysis (CGDE) technique, and then used as an electrode material for the pseudocapacitor.