NiCo₂S₄ Nanowire Arrays VerticallyGrown on Carbon Paper by Utilizing a Ni Seed Layer for Ammonia Oxidationin 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.