Chi150

An electrochemical workstation with three-electrode system was used to test the catalytic performance of the catalysts. The electrochemical workstation used for the experiments was manufactured by Shanghai Chenhua, model CHI760E. The three electrodes in order are saturated calomel electrode as reference electrode, model CHI150; platinum wire electrode as counter electrode, model CHI115; and glass carbon electrode as working electrode, model CHI104, three electrodes were purchased from Shanghai Chenhua Company. The working electrode is prepared as follows: using in turn 0.3 μm and 0.05 μm AI₂O₃ powder, the electrode is polished on a flannel with the aim of the glassy carbon to a mirror-like surface without scratches and the PTFE material wrapped around the glassy carbon to a very hydrophobic surface. Weigh 10 mg of catalyst to be tested, add to a mixture solution of 2.4 mL ultrapure water, 0.1 mL Nafion, 2.5 mL C₃H₈O and sonicate for 30 min to obtain a 2 mg mL⁻¹ slurry of catalyst. 5 μL of slurry was added to the glassy carbon electrode using a pipette gun and allowed to dry naturally as a working electrode.

The voltage through the external resistor was collected with a digital multimeter (model 2700, Keithley Instruments, Inc., Cleveland, OH) at every 15 min.^{20,21 (link)} The anode and cathode potentials were determined via a saturated calomel electrode (SCE, CHI150, Chenhua Co, Shanghai, China), respectively. Chemical oxygen demand (COD) was measured using the dichromate standard method.^{20,21 (link)} The pH values were measured with a pH meter (FE 20, Mettler Toledo, Swiss). The biomass on the anodic and cathodic biofilm was determined using the Coomassie brilliant blue method.^{9 (link)} Biogas from the MEC was collected with sampling bags (each 0.15 L capacity, Shanghai ELOR Co., Ltd., China). The gas composition in the biogas was analyzed using gas chromatography (GC 2014, Shimadzu Co., Japan) equipped with a thermal conductivity detector.^{22 (link)} The high purity argon was the carrier gas at a flow rate of 10 mL min⁻¹.^{9 (link)}