Performance of metal alloys as hydrogen evolution reaction catalysts in a microbial electrolysis cell

H2 can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease the energy input and increase the H2 production rate of an MEC, a catalyst is used at the cathode. Platinum is an effective catalyst, but its high costs stimulate searching for alternatives, such as non-noble metal alloys. This study demonstrates that copper sheet coated with nickel-molybdenum, nickel-iron-molybdenum or cobalt-molybdenum alloys have a higher catalytic activity for the hydrogen evolution reaction than nickel cathodes, measured near neutral pH. However, the catalytic activity cannot be fully exploited near neutral pH because of mass transport limitation. The catalytic activity is best exploited at alkaline pH where mass transport is not limiting. This was demonstrated in an MEC with a cobalt-molybdenum coated cathode and anion exchange membrane, which produced 50 m3 H2 m-3 MEC d-1 (at standard temperature and pressure) at an electricity input of 2.5 kWh m-3 H2.