Enhanced performance of bioelectrochemical hydrogen production using a pH control strategy

The use of membranes in microbial electrolysis cells (MEC) is required to obtain high-purity hydrogen and to avoid the consumption of hydrogen by undesired microorganisms. However, its utilization results in pH gradients across the membrane that contribute to potential losses and reduce the efficiency of MEC. Several pH-controlled and noncontrolled scenarios were evaluated in this work, which evidenced that pH control is beneficial for the MEC performance. The best results were obtained if the anodic and cathodic pH were controlled at 7.5 and 2.0, respectively, to produce 0.58 m(3)  m(-3)  d(-1) of hydrogen at an applied voltage of only 0.2 V. The energy efficiency with respect to the electrical input was increased up to 883 %. Anodic pH control allowed us to maintain a stable exoelectrogenic activity with practically constant current intensity, whereas cathodic pH control at 2.0 allowed a fivefold decrease of the required electrical input, which opens new opportunities for the economy of its full-scale application.