Enhanced Wettability Improves Catalytic Activity of Nickel-Functionalized Activated Carbon Cathode for Hydrogen Production in Microbial Electrolysis Cells

Impact of Current Collectors with Different Electrocatalytic Activities on Hydrogen Production in Microbial Electrolysis Cells with Flowable Cathodes

“…%). 6 The enhanced HER activities obtained in the present study with the higher Ni/AC loadings were likely due to the promoted HER activities with the greater Ni catalyst loading (i.e., 4 at. %) on AC particles.…”

“…Fully acclimated microbial anodes from our previous MEC study were used from the beginning of our experiments for this study. 6 MECs were operated at least 3 cycles (4 h for a cycle) under each condition to examine hydrogen production rates at an applied voltage of 0.9 V using a direct-current (DC) power supply (BK precision, model: 1621A). Detailed cathodic and anodic chamber operation, including MEC current density recording, is described in the Supporting Information.…”

“…Ni/AC catalysts were synthesized by a hydrothermal method as previously described. 6 The resulting powders contained 4 atom % of nickel loaded on the AC surface (or 16.9 wt % of nickel). Ni/AC flow cathodes with different current collectors were expressed as X-Ni/AC Y , where X is the current collector material (NF, SS mesh, or Ti plate) and Y is the Ni/AC powder loading (weight of Ni/AC powder per the volume of the catholyte, wt %).…”

“…5 To overcome this limitation, the recent study reported a binder-free Ni/AC flowable cathode, the suspended Ni/AC particles were used as cathode materials with continuous recirculation near the current collector. 6 Ni/AC flow cathodes with minimal catalysts mass loading (0.125 wt %) displayed comparable H 2 production rates (1.62 ± 0.15 L-H 2 /L-d) to the solid-type Pt cathode (0.5 mg-Pt/cm 2 , 1.64 ± 0.09 L-H 2 / L-d). The Ni/AC flow cathodes enabled H 2 production rates with Ni/AC flow cathodes 5 times higher than those with Ni/ AC solid-type cathodes for MECs.…”

“…The hydrogen production rates achieved here with the NF-Ni/ AC 0.125 flow cathode were 133% higher than those previously obtained with an NF cathode in a MEC (1.0 ± 0.1 L-H 2 /L-d) under similar configuration and catholyte conditions (twochamber MEC, 50 mM PBS catholyte used with recirculation), and 44% higher than our previous Ni/AC flow cathode study (1.6 ± 0.15 L-H 2 /L-d) using SS mesh as a current collector. 4,6 NF enabled the highest energy yield when coupled with Ni/ AC 0.125 flow cathode (ηE, 186 ± 13%) in comparison with SS-Ni/AC 0.125 (173 ± 15%) and Ti-Ni/AC 0.125 (168 ± 9%) over the cycles (Figure S4 and Table S2). The energy yields of the MECs with Ni/AC flow cathodes gradually decreased as the concentration of the Ni/AC flow cathode increased (Figure S4 and Table S2), likely because of the lower cathodic H 2 recovery efficiencies (r cat .…”