Electrodeposition of a Porous Spherical Nickel Nanocatalyst by Pulsed Electrodeposition with External Heating for Ammonia Oxidation in Direct Ammonia Fuel Cells

Nickel (Ni) as a non-precious metal catalyst is gradually emphasized in direct ammonia fuel cells (DAFCs). However, a Ni catalyst has poor electrocatalytic activity in the ammonia oxidation reaction. Herein, a Ni nanocatalyst with a spherical and porous structure is successfully prepared on a carbon paper electrode by a pulsed electrodeposition method under a thermal bath. After the pulsed electrodeposition at 55 °C, the porous spherical Ni nanoparticles are deposited on the carbon fiber surface to enlarge the electrochemically active surface area and increase reaction active sites compared to the two common electrodeposition methods of constant current and constant potential. As a benefit from the unique structure, the prepared Ni electrode demonstrates superior electrochemical performance with a low charge transfer resistance and high reaction rate of ammonia oxidation. In addition, a direct ammonia microfluidic fuel cell (DAMFC) with the prepared Ni electrode as the anode and the catalyst-free hydrophilic carbon paper as the cathode achieves prominent cell performance. The peak power density and open circuit voltage of the DAMFC are 27.67 mW cm–2 and 1.2 V, respectively. Results show that a facile preparation approach for the Ni electrode owning porous spherical nanoparticles, which improves cell performance and ensures low cost, is provided for DAFCs.