Understanding the impact of sintering temperature on the physical and chemical properties of Ni-BaCe_0.54Zr_0.36Y_0.1O_3-δ (Ni-BCZY) composite anode is worthy of being investigated as this anode is the potential for protonic ceramic fuel cell (PCFC) application. Initially, NiO–BCZY composite powder with 50 wt% of NiO and 50 wt% of BCZY is prepared by the sol–gel method using citric acid as the chelating agent. Thermogravimetric analysis indicates that the optimum calcination temperature of the synthesised powder is 1100 °C. XRD result shows that the calcined powder exists as a single cubic phase without any secondary phase with the lattice parameter (a) of 4.332 Å. FESEM analysis confirms that the powder is homogeneous and uniform, with an average particle size of 51 ± 16 nm. The specific surface area of the calcined powder measured by the Brunauer–Emmett–Teller (BET) technique is 6.25 m²/g. The thickness, porosity, electrical conductivity and electrochemical performance of the screen-printed anode are measured as a function of sintering temperature (1200–1400 °C). The thickness of the sintered anodes after the reduction process decreases from 28.95 μm to 26.18 μm and their porosity also decreases from 33.98% to 26.93% when the sintering temperature increases from 1200 °C to 1400 °C. The electrical conductivities of the anodes sintered at 1200 °C, 1300 °C and 1400 °C are 443 S/cm, 633 S/cm and 1124 S/cm at 800 °C, respectively. Electrochemical studies showed that the anode sintered at 1400 °C shows the lowest area specific resistance (ASR) of 1.165 Ω cm² under a humidified (3% H₂O) gas mixture of H₂ (10%) and N₂ (90%) at 800 °C. Further improvement of the anode’s performance can be achieved by considering the properties of the screen-printing ink used for its preparation.

Solid oxide fuel cells (SOFCs) can efficiently convert chemical fuels into electricity, but stable anode operation with hydrocarbon and ammonia fuels remains challenging. Conventional nickel (Ni)-based anodes are prone to carbon deposition, sulfur poisoning, and redox instability, which has stimulated the development of nickel-free (Ni-free) alternatives. This review summarizes the electrochemical conversion pathways of hydrocarbon and ammonia fuels and the limitations of Ni-based anodes under these conditions. Ni-free anode materials are then evaluated against a common set of criteria: surface and defect chemistry, fuel activation, electrochemical performance, carbon tolerance, and structural stability. Within this framework, hydrocarbon activation, carbon formation and removal, and degradation under carbon-based fuels are discussed with particular attention. Among the Ni-free materials, perovskite and double-perovskite oxides provide compositional flexibility with good redox activity, whereas ceria-based fluorite oxides offer favorable oxygen storage and transport properties. Beyond these oxide families, exsolution-derived oxides and oxide composites can generate active interfaces that promote fuel conversion and carbon removal. However, no single material family currently combines high activity, carbon tolerance, and long-term stability under all operating conditions. Therefore, future work should focus on anode operation under realistic fuel conditions, long-term durability and interfacial stability during thermal cycling, and scalable manufacturing routes.