Impact of ball-milling of carbide-derived carbons on the generation of hydrogen peroxide via electroreduction of oxygen in alkaline media

Abstract

Ball-milling is an effective method to decrease the size of carbide-derived carbon (CDC) grains, but milling might also affect other properties of CDC materials including but not limited to specific surface area (SSA), porosity, elemental composition and electrochemical properties. Thus, the goal of this work is to ball-mill various CDCs synthesised from silicon or titanium carbides and explore the effect of milling conditions on their physico-chemical and electrochemical properties. N 2 physisorption studies reveal that small ZrO 2 beads (0.5 mm in diameter) affect the SSA much less than bigger balls (5 mm in diameter) and the total porosity increases in the milled CDCs as compared to the initial microporous CDC materials referring to the formation of mesopores. Scanning electron microscopy (SEM) studies show that the morphology of the ground CDCs resembles that of submicron carbon powder. Slight changes regarding the total content of oxygen-containing groups on CDCs after grinding was confirmed by X-ray photoelectron spectroscopy (XPS). No significant change was observed between the activity of the initial and ball-milled CDCs towards the oxygen reduction reaction (ORR) in alkaline media by rotating ring-disc electrode (RRDE) method. The ORR on CDCs proceed via 2 + 2e − mechanism: O 2 reduction to HO 2 − followed by further electroreduction of HO 2 − to OH − . • Ball-milling with small beads (0.5 mm) have drastic impact on the CDC's morphology. • High specific surface area of CDC materials is maintained if small beads are used. • The electrocatalytic ORR activity slightly improved after ball-milling of CDCs. • Pristine and ball-milled CDCs produce high yield of HO 2 − at low overpotentials.