Thermochemical metal/metal oxide redox reactions have twice the energy density of 2,4,6-trinitrotoluene (TNT). They suffer, however, from low pressure-volume work due to low gas expansion from the reaction. This study focuses on the development of a nanocomposite that delivers a high energy density and the potential of rapid gas release. Hollow CuO spheres with nanosized building blocks are fabricated using a “droplet-to-particle” aerosol spray pyrolysis method with the introduction of gas-blowing agents in the synthesis procedure. Nanoaluminum with hollow CuO as an oxidizer ignites in a very violent manner and exhibits excellent gas-generation behavior, demonstrating a high pressurization rate of 0.745 MPa μs−1 and a transient peak pressure of 0.896 MPa with a charge density of 1 mg cm−3, as well as a rapid oxygen release. Compared with wet-chemistry methods, gas-phase processes are relatively low cost, nominally offer a higher purity product, and are usually configured as continuous production processes, with a limited number of steps. The synthesis strategy demonstrated is simple and should be extendable to the preparation of other hollow metal oxide structures.