The desire to form supported nanoparticles with fine-tuned size and distribution motivates the application of speciation-control of precursors. We propose to use a ternary metal ion/polyelectrolyte/oxide support hybrid as the means to generate a controlled precursor species. We first modify alumina with poly(acrylic acid), followed by nickel ion sorption to generate catalyst precursors. The precursors are then converted to catalysts used in CO2 methanation. The parameters of polyelectrolyte incorporation are found to play a critical role in determining the resultant catalyst performances. The application of polyelectrolyte in assisting metal nanoparticle formation on oxide support emerges as a versatile, potentially universal, and industrially relevant approach to manufacturing heterogeneous catalysts..