High surface area tin oxide nanocrystals prepared by a facile hydrothermal method are evaluated as electrocatalysts toward CO2 reduction to formate. At these novel nanostructured tin catalysts, CO2 reduction occurs selectively to formate at overpotentials as low as similar to 340 mV. In aqueous NaHCO3 solutions, maximum Faradaic efficiencies for formate production of > 93% have been reached with high stability and current densities of > 10 inA/cm(2) on graphene supports. The notable reactivity toward CO2 reduction achieved here may arise from a compromise between the strength of the interaction between CO2 center dot- and the nanoscale tin surface and subsequent kinetic activation toward protonation and further reduction.