NiCo₂S₄ Nanowire Arrays Vertically Grown on Carbon Paper by Utilizing a Ni Seed Layer for Ammonia Oxidation in High-Cost-Performance Direct Ammonia Fuel Cell

Direct ammonia fuel cell (DAFC) as a carbon-free energy conversion equipment attracts widespread attention; however, its development is limited by the sluggish kinetic rates of ammonia oxidation reaction (AOR) at room temperature and the high cost of precious metal catalysts. Thus, NiCo2S4 nanowire arrays vertically distributed on carbon paper (CP) with a Ni seed layer (Ni@NiCo2S4/CP) are successfully synthesized by cyclic voltammetry electrodeposition and hydrothermal method. Its unique physical structure not only enlarges the electrochemically active surface area to expose abundant active sites but also reduces the electron–ion transport path and enhances the electron transfer speed and the synergistic catalysis of Ni and Co of NiCo2S4, greatly improving the catalytic activity and stability of the electrode for the AOR. In addition, a low-cost membraneless DAFC with a catalyst-free CP cathode and a Ni@NiCo2S4/CP anode is constructed and delivers outstanding cell performance at room temperature. The peak power density of the fuel cell reaches 33.3 mW cm–2, 3.3 times that of the DAFC with the Ni/CP anode. The results show that the Ni@NiCo2S4/CP electrode is a potential anode for DAFC due to its low cost, high performance, and excellent stability.