Electrochemical carbon dioxide (CO2) reduction, ideally in an aqueous medium, accounts for the sustainable storage of energy from renewable sources in the form of chemical energy in fuels or value-added chemicals. Herein, we report boron and nitrogen co-doped carbon nanosheets encapsulating iron nanocrystals (Fe/BCNNS) as a low cost, highly efficient and precious-metal-free electrocatalyst for the electrochemical reduction of carbon dioxide to formic acid. The porous architecture of the boron and nitrogen co-doped carbon nanosheets along with the active Fe–Nx, N and B sites synergistically allow better three phase contact to enhance the electrocatalytic activity of the cell. Both half-cell as well as full cell measurements have been performed with this particular catalyst. The proton exchange membrane (PEM) CO2 conversion cell is tested under a continuous flow of CO2 gas and is demonstrated to selectively produce a high yield of formic acid due to improved interaction between the catalyst and gas molecules. The maximum yield of formic acid achieved is as high as 94% after 60 min of reaction with Fe/BCNNS as both anode and cathode catalysts. It can be anticipated that such a facile synthesis strategy and excellent electrocatalytic performance of low-cost Fe/BCNNS catalyst can be easily scaled up for industrial applications in electrochemical CO2 conversion. © 2019