Invisible active sites of Ni-Co alloy to toluene pyrolysis and hydrogen production at ultra-low temperature

Abstract

Environmental problems caused by the utilization of fossil energy are becoming more and more serious, so now more attention has been paid to the use of renewable energy. Pyrolysis of biomass is a method that convert biomass energy into hydrogen, but this method is subject to the performance of the catalyst for the pyrolytic reaction. In this study, NiCo2O4 was synthesized by coprecipitation method and examined by microstructure and textual characterizations. The ability of NiCo2O4 to pyrolyze toluene and produce hydrogen was evaluated by temperature-programmed experiment and lifetime test. It was found that the sample could pyrolyze toluene at the concentration of 1500 ppm at 300 °C with a hydrogen production of 0.6%, suggesting toluene was completely pyrolyzed. In the longevity test, toluene can be completely pyrolyzed for at least 5 h at 400 °C, with a high hydrogen yield of above 80% maintained during the pyrolysis process. As the pyrolysis reaction progresses, NiCo2O4 was gradually reduced to nickel-cobalt alloy by hydrogen from the pyrolysis of toluene, indicating the actual active site of nickel-cobalt alloy. This study gives a hint for developing a good catalyst for the ultra-low temperature biomass pyrolysis to produce hydrogen.