Fluke 87 5

OCP experiments were performed to investigate the effect of deployment depth on the OCP in soil reactors (Fig. 1A). OCP measurements were recorded daily for each electrode using a digital voltmeter (Fluke 87-V, Fluke Corporation, Everett, WA). OCP measurements were recorded for a minimum of 18 days and continued until stable OCP values are established. Data are reported as means and standard deviations of four biological replicates.

Electrofiltration experiments were conducted using a cross-flow membrane filtration system (Supplementary Fig. 8). The membrane system consists of a 12-mL feed chamber and a 12-mL permeate chamber. Pd–Pt–CM was inserted in-between the feed and permeate chambers; Pd–CM surface faced the feed chamber, while Pt–CM surface faced the permeate chamber. The Pd–CM and Pt–CM surfaces serving as cathode and anode, respectively, were connected to a DC supply (E3617A, HEWLETT PACKARD) via carbon tape. Porous titanium (Ti) mesh plate with an identical surface area as Pd–Pt–CM (17.34 cm²) was placed in each chamber and used as a counter electrode in specific flow-through modes (i.e., mode II and III in Fig. 3b). A constant voltage of 1.6 V was applied to the Pd–Pt–CM throughout the filtration experiments, and a multimeter (Fluke 87-V, Everett, WA) was used for current measurement.
Experiments were carried out in flow-through and flow-by modes. For each mode, feed solution was circulated between the feed chamber (i.e., Region B in Fig. 2a) and feed reservoir (i.e., Region A in Fig. 2a) at a flow velocity of 0.8 L min⁻¹ by a gear pump (Cole-Parmer Instrument Company, Vernon Hills, IL, USA). In flow-through mode, the feed solution flowed through the membrane at a constant transmembrane pressure of 0.1 bar, while in the flow-by mode, the feed solution flowed tangent to the membrane surface.