Advances, progress and challenges of NiCo₂O₄-based composite materials for direct methanol fuel cell applications: A critical review

Fuel cells are promising fossil fuel alternatives that are both environmentally friendly and powerful. Direct methanol fuel cells are particularly suitable for lightweight cars and portable electronics. Developing efficient, cost-effective, and eco-friendly catalysts for energy storage and conversion devices is vital for long-term energy security. Numerous studies have explored using metal oxides and modifications to mixed transition metal oxide (MTMO)-based catalysts to enhance the methanol oxidation process. Coupling transition metals (Mn, Co, Ni, Fe, Zn, etc.) in MTMOs improves redox processes and electronic conductivity, advancing electrochemical applications. Among these, nickel cobaltite (NiCo2O4) stands out due to its material stability and higher electronic conductivity compared to single-component metal oxides NiO and Co2O4. NiCo2O4 shows great potential as a composite-based material for fuel cell applications. This paper reviews studies on NiCo2O4 as composite-based materials for electrocatalysts, including various methods for synthesizing nanostructures suitable for direct methanol fuel cells. It also highlights the challenges and potential benefits of using NiCo2O4 in practical energy storage systems, offering valuable perspectives and insights for early-stage researchers focused on future research and development in composite-based materials for energy applications.