In this chapter, the development of natural materials including rare-earth oxide, hematite ore, CuFe oxide minerals, and bio-derived calcite for electrolyte-free fuel cell (EFFC) application is introduced. The natural materials are shaped into fuel cell electrolyte layer in a form of semiconducting-ionic composites, which are investigated by material characterization, electrochemical analysis, electrical conductivity, and fuel cell performance measurements to show their feasibilities and great potentials in EFFCs. The correlation between material compositions and fuel cell performance has been specially studied, and in some typical cases particular attention is given to the stability and working mechanism of the fuel cell devices. To sum up, the design of semiconducting-ionic composites based on these natural materials indicates a promising strategy for developing cost-effective material for high-performance EFFCs.