CO2 emission from the processing of fossil fuels for energy generation is a major contemporary challenge to the climate change. The chemical transformation of CO2 to high-energy molecules is an avenue to alleviate this problem, and, therefore, the electrochemical reduction of CO2 has attracted wide interests. The co-electrolysis of CO2 and H2O using high temperature solid oxide electrolysis cells (SOECs) to produce syngas and hydrocarbons is a potential way to transform CO2 to valuable products [2, 3]. At the cathode of the SOEC, CO2 and H2O are reduced to CO, H2, and oxygen ions. The oxygen ions diffuse through the electrolyte to the anode to be evolved as O2. The traditional cathode material for these electrochemical systems is Ni due to good electrical conductivity, thermal compatibility with the other cell components and low cost. The challenge with Ni is the high overpotential losses induced by its limited ability to electrochemically reduce CO2. In the present work, we focus on improving the electrochemical activity of the Ni catalyst by alloying it with another metal. We have used density functional theory (DFT) calculations to calculate the energetics associated with CO2 and H2O co-electrolysis on various Ni alloys. The binding energies of intermediates and the barriers of elementary steps are determined. In addition, the rates of CO2 activation and H2O dissociation are obtained using microkinetic modeling analysis. We found a “volcano” type relationship between the calculated electrochemical rates and the binding energy of O on the different Ni alloys. The predictions from the DFT calculations are supported by experimental studies using solid oxide electrolysis cells.
1.Q. Lu, J. Rosen, Y. Zhou, G. S. Hutchings, Y. C. Kimmel, J. G. G. Chen, F. Jiao, Nat. Commun. 2014, 5, 3242
2.Z. L. Zhan, W. Kobsiriphat, J. R. Wilson, M. Pillai, I. Kim, S. A. Barnett, Energy & Fuels 2009, 23, 3089
3. K. Xie, Y. Q. Zhang, G. Y. Meng, J. T. S. Irvine, Energy Environ. Sci. 2011, 4, 2218