Nanoparticles of indium, indium hydroxide, and indium oxide were synthesized and evaluated for their electrocatalytic abilities in the reduction of CO2 to formate. These nanoparticles were characterized with several microscopic and spectroscopic techniques in order to investigate their structure and surface features. Their electrochemical behavior was also probed through voltammetry and bulk electrolysis. faradaic efficiencies approaching 100% were achieved on these particles at potentials as positive as -1.3 V vs. Ag/AgCl, which represents a significant decrease in the overpotential compared to that observed using bulk indium electrodes. The nanostructuring of the particles and the partial surface oxidation of the indium nanoparticles to yield catalytic surface indium hydroxide species are implicated in the high efficiencies at low overpotentials. (C) The Author(s) 2016. Published by ECS. All rights reserved.