Reaction milling for scalable synthesis of N, P-codoped covalent organic polymers for metal-free bifunctional electrocatalysts

This study exploits an effective mechanochemical process (termed as reaction milling) to conduct Schiff-based coupling reaction with melamine and terephthalaldehyde for the synthesis of covalent organic polymer (RM-COP) as the carbon skeleton and the derivative phosphorus doped material (RM-COP-PA). Comparing with the tradition solvothermal method with reaction time of 3 days under 120 °C, the newly developed reaction milling method significantly shorten the reaction time of the synthesis to 3 h under room temperature as well as bypassing the usage for hazardous solvents. The space-time yield of the developed reaction milling method for synthesis of the bifunctional electrocatalytic precursor reaches 189 kg m −3  day −1 . Significantly, the optimal products followed by further carbonization (RM-COP-PA-900) demonstrated excellent bifunctional electrocatalytic activities for an efficient ORR performance with similar commercialized Pt/C half-potential of 841 mV vs RHE as well as an IrO 2 -like OER activity with a potential of 1.69 V at 10 mA cm −2 in alkaline media, which is better than most metal-free bifunctional catalysts. Moreover, the obtained RM-COP-PA-900 exhibits much better durability and resistance to crossover effect even than the commercial 20 wt% Pt/C catalysts. Therefore, this work will open up a rapid, solvent-free and scalable approach for, but not limit to, highly efficient electrocatalysts.