With relatively little effort, copper, a low-cost and plentiful element, can be converted from a mediocre catalyst for converting CO2 to liquid fuels to a good one. Several metals can be used as electrocatalysts for converting CO2 to CO. But few of them do a good job transforming CO to fuel-worthy liquids. In an electrochemical cell, copper electrodes can mediate that conversion step, but the chemical selectivity and energy efficiency are too low for practical use. Stanford University’s Christina W. Li and Matthew W. Kanan show that copper can do a better job at CO conversion if the metal is first oxidized in air to form a Cu2O layer and then reduced either electrochemically or by treatment with hydrogen. Specifically, the team shows that compared with a nanocrystalline copper reference electrode, Cu2O-derived materials of comparable particle size produce ethanol more selectively and with lower energy input (Nature 2014, DOI: 10.1038/nature13249). The team proposes that the enhanced performance stems from unique properties of the grain boundaries (interfaces) between nanoparticles of the Cu2O-derived materials.