Nickel powder blended activated carbon cathodes for hydrogen production in microbial electrolysis cells

Although pure Ni catalysts can achieve a hydrogen production rate similar to Pt in microbial electrolysis cells (MECs), a reduction in the amount of Ni used is needed to reduce the cost. In this study, nickel powder (pNi)was blended with activated carbon (AC)to reduce the mass of Ni used, while improving catalytic activity for the hydrogen evolution reaction (HER)by increasing the active surface area. Ni powder blended AC cathodes (AC-pNi)were fabricated at different nickel powder loadings (4.8, 19, 46 mg/cm² with AC and 77 mg/cm² without AC as control). AC-pNi4.8 (Ni loading: 4.8 mg/cm²)produced higher hydrogen production rates (0.38 ± 0.04 L-H₂/L-d)than pNi77 (0.28 ± 0.02 L-H₂/L-d)with a 16 times less Ni loading. Cathodic hydrogen recovery of using the AC-pNi4.8 (98 ± 5%)was also higher than pNi77 (82 ± 4%), indicating catalytic activities were improved by AC blending. Nickel dissolution into the catholyte after completion of each cycle was negligible for AC-pNi4.8 (<0.2 mg/L), while Ni dissolution was detected for pNi77 (5–10 mg/L). These results indicate that AC blending with Ni powder can improve hydrogen production in MECs while minimizing the amount of Ni in the cathode.