Table 1.

Summary of reactor designs and experimental program.

Configuration	Objective	Voltage delivered (V)	Cathode potential [V vs. standard hydrogen electrode (SHE)]
H-cells	H-cells poised at different cell potentials	3.0, 3.5, 5.0	-0.65, -0.71, -0.74
Abiotic	Measure hydrogen production in the absence of microbes	3.5	-0.79
Membrane-less	Decrease resistance of the reactors to increase energy efficiency	1.9 to 2.5	-0.70 to -0.81