Effects of Different Ni-Fe/Ni Foam Catalysts on In Situ Preparation of CNTs@Ni Foam Electrode Materials and H2 during Steam Reforming of Pyrrole

Abstract

New catalysts of Ni–Fe loading Ni foam (Ni–Fe/NF) were used in catalytic reforming of pyrrole for the co-production of H2 and CNTs@Ni foam electrode materials. Ni–Fe/NF with different Fe/Ni ratios (0.5, 1, 2, and 3) and Ni/NF and Fe/NF catalysts were tested. The Ni–Fe alloy was formed on Ni–Fe/NF and remarkably promoted pyrrole conversion and H2 yield. They showed a trend of first increasing and then decreasing with the increase of the Fe/Ni ratio, and the N1F2/NF (Fe/Ni ratio is 2) reached the maximum. The H2 yield over N1F2/NF was 20 times larger than that over Ni/NF and Fe/NF. The high amount of Fe–Ni alloy with a small crystallite size boosted the catalytic activity of Ni–Fe/NF. After the reforming reaction, large amounts of CNTs were observed on the surface of Ni foam’s skeleton network. The structures of CNTs@Ni foam were prepared and promoted by the Ni–Fe alloy. It proved that the CNTs on Ni–Fe/NF catalysts follow the tip-growth and vapor–liquid–solid (VLS) mechanisms. The Ni–Fe alloy contributed to the formation of liquid carbide and carbon intermediates, thus promoting the CNTs’ growth. Compared with the pristine Ni foam, the prepared CNTs@Ni foam materials showed excellent electrochemical performance and had promising application potential in supercapacitors. The spent N1F1/NF (Fe/Ni ratio is 1) showed the best charging and discharging capacity.