Electrochemical reduction of CO2, as a promising solution to the rising atmospheric CO2 levels, can help convert CO2 into value-added chemical feedstocks in a sustainable fashion Moreover, powered by solar and other sources of renewable electricity, the electrochemical reduction of CO2 provides a strategy to store these intermittent sources of energy into high-energy chemicals using hydrogen source obtained from electrolysis of water.
Unluckily, limited from the lack of excellent electrocatalysts, this technology is still difficult to be commercialized on a large scale.
Prof. ZENG Jie's group, collaborating with Prof. YANG Jinlong from University of Science and Technology of China of Chinese Academy of Sciences, revealed the strain effect in electrochemical reduction of CO2. By using Pd octahedra and icosahedra as a well-defined platform, they demonstrated the internal correlation between surface strain and catalytic performance in the electrochemical reduction of CO2. This study was published in Angewandte Chemie International Edition.
To enhance the efficiency of energy conversion, it is important to strengthen the adsorption and activation of inert CO2. That’s why a rational design of highly active and robust electrocatalysts matters.
Among all the structure parameters in heterogeneous catalysts, surface strain is generally generated by the lattice mismatch between different kinds of compositions and some twin structures like icosahedra. Modulating the surface strain is proved to be a powerful method to regulate the catalytic properties of heterogeneous catalysts. However, a clear and systematic understanding of strain effect in electrochemical reduction of CO2 is still lacking.
Researchers designed an ideal platform based on Pd octahedra and icosahedra to explore the strain effect on the activity in CO2 electrochemical reduction. They found that the Pd icosahedra/C catalyst shows a maximum Faradaic efficiency for CO production of 91.1% at -0.8 V versus reversible hydrogen electrode (vs. RHE), which is 1.7-fold higher than the maximum Faradaic efficiency of Pd octahedra/C catalyst at -0.7 V (vs. RHE).
In short, the Pd icosahedra/C catalyst shows a much higher catalytic activity towards electrochemical reduction of CO2 with respect to the Pd octahedra/C catalyst.
They further used molecular dynamics (MD) simulations and density functional theory (DFT) calculations revealing the improvement in catalytic activity stems from the tensile strain on the surface of Pd icosahedra, which shifts up the d-band center and thus strengthens the adsorption of key intermediate COOH*.
This work not only provides an in-depth understanding of the strain effect but also offers an effective knob to tune the catalytic properties for electrochemical reduction of CO2.