Spatially confined atomic dispersion of metals in thermally reduced graphene oxide films

Incorporating homogeneously dispersed metal single atoms or nanoclusters into bulk matrix can produce functional materials for electrochemical catalysis, energy storage, and electronic devices. However, the instability of single metal atoms (or clusters) against agglomeration and thus loss of active surfaces during high-temperature treatment or reactions remains a major challenge. Here, we report the effect of spatial confinement on suppressing migration and coalescence of metal atoms/clusters in solid films made of stacked and/or overlapping (‘reduced’) graphene oxide, resulting in increased stability of dispersed metal (i.e., Cu, Co, Ni) atoms and nanoclusters at high temperature (1000 °C). We find that pressing has a significant impact on the degree of ‘reduction’ of graphene oxide and the morphology and distribution of metals in the films; the presence of metals influences the thermal ‘reduction’ and graphitization of graphene oxide. This work demonstrates the efficacy of externally applied pressure in controlling the reactivity and mobility of metal atoms/clusters in bulk solids, which can be a useful means for preparing a variety of atomic/nano-metal-based hybrid materials.