Encapsulated cobalt-doped Ni3C in Carbon layers as bifunctional electrocatalyst for hydrogen and oxygen evolution

• Main Author: Kang, Aldrin Min Shing
• Other Authors: Alex Yan Qingyu
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Materials::Energy materials
• Online Access: http://hdl.handle.net/10356/76805
• Institution: Nanyang Technological University

Due to depleting fossil fuels and climate changes, research efforts have been put into exploring low cost and highly efficient renewable energy such as electrocatalytic water splitting that has promising applications in metal-air batteries and fuel cells. In this project, it aims to study the effects of cobalt-doping in Ni3C as a bifunctional electrocatalyst for hydrogen and oxygen evolution reactions (HER and OER). Encapsulated nickel carbide (Ni3C) and cobalt-doped nickel carbide (Co-Ni3C) in carbon layers were prepared by subjecting Co-doped and bare nickel-based coordination polymers (NiCP) to a facile co-precipitation process follow by carburization. TEM analysis showed that the uniform Co-Ni3C and undoped Ni3C nanospheres enclosed in N-doped carbon layers of 3 nm had a size difference of about 30%, represented by a contrasting average nanoparticle diameter of 37.5 nm and 54.5 nm, respectively. When doped with Co, Co-Ni3C exhibited better HER and OER performance than bare Ni3C. Under an alkaline environment, to reach a current density of 10 mA cm-2, Co-Ni3C required a lower overpotential of 200 mV for HER and 300 mV for OER compared to Ni3C which had 245 mV for HER and 340 mV for OER. Tafel slopes of 106 mV dec-1 for HER and 76 mV dec-1 for OER were also exhibited by Co-Ni3C, which represented a better performance than Ni3C that had 126 mV dec-1 for HER and 156 mV dec-1 for OER. Therefore, this proved that Co-doping improved the surface composition and electronic properties of Co-Ni3C, providing more active sites for electrocatalysis. It had also demonstrated high stability, without noticeable degradation, based on the results of a 12 hours potentiostatic test.