Highly selective electrochemical reduction of CO2 to HCOOH on a gallium oxide cathode

We report on the high-selectivity electrochemical reduction of CO2 to formic acid (HCOOH) using conductive single-crystal Ga2O3. Single-crystalline Sn- or Si-doped Ga2O3 was manufactured using an edge-defined film-fed growth method. The stability of Ga2O3 was confirmed over fifty cyclic voltammetry cycles. In our electrolysis experiments, a Ga2O3 cathode selectively produced HCOOH with a Faradaic efficiency of over 80% by electrochemical reduction of CO2. A possible intermediate state is simulated based on density function theory. Our calculations show the so-called formate on Ga2O3 to be a possible intermediate state in the reaction from CO2 to HCOOH. (C) 2014 Elsevier B.V. All rights reserved.