Synthesis of NiY zeolite and hydrogen evolution performance in cathode of a microbial electrolysis cell

NiY zeolites were synthesized in the system of Na₂O-Al₂O₃-SiO₂-H₂O with the addition of nickel nitrate by crystallization directing agent and characterized by XRD, SEM, TEM, N₂ adsorption-desorption, etc. The results show that the crystallinity and zeta potential decrease after an increase at first with the increasing of nickel added. It means that nickel nitrate can promote the formation of molecular sieve when Si/Ni(mol ratio) is greater than 5, while it has an inhibitory effect when Si/Ni(mol ratio) is less than 5. The NiY zeolites with 1.5-3 μm of size not only possess special morphology, six or four square columns with grooved structure, but also have a multiple porous structure including microporous and mesoporous. The sample test by cyclic voltammetry (CV) and polarization curve(LSV) in microbial electrolysis cell (MEC) indicates that the NiY zeolites with Si/Ni(mol ratio)=5 present the best electrochemical characteristics with an outstanding redox performance, a minimum overvoltage and the highest electrocatalytic activity. Moreover, the hydrogen production yield reaches 10.1 mL/4 mg in 12 h with the hydrogen purity of 81.69%, surpassing that with Pt electrodes by about 28%. It suggests that the NiY zeolites have a better hydrogen evolution activity and it is possible to replace Pt as a novel cathode catalyst in microbial electrolysis cell.