Room-temperature electrocatalytic hydrogenation of acetylene to ethylene


Recently, a research group led by Prof. DENG Dehui from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) reported a highly efficient electrocatalytic hydrogenation of acetylene to ethylene (E-HAE) under room temperature by directly using water as hydrogen source.

Ethylene, as one of the most important building blocks in chemical synthesis, is mainly produced from naphtha cracking at high temperatures of around 800 oC. Considering that our country is poor in oil but rich in coal, it is of strategic importance to develop highly efficient ethylene production route from hydrogenation of coal-based acetylene. However, thermocatalytic HAE typically requires high temperatures above 200 °C and high pressures of around 5 bar, and thus is highly energy demanding and may cause excessive hydrogenation of acetylene to ethane. Besides, large amount of H2 consumption makes the process even more costly. Therefore, it is of great significance to develop a more economical, energy-efficient, and highly selective route for the HAE process.

Figure 1. The features of the electrocatalytic HAE (E-HAE) process compared with the traditional thermocatalytic HAE process.

In this work, the researchers developed a room-temperature E-HAE process. In contrast to the thermocatalytic path, this process is advantageous in being operatable under mild conditions and is environmental-friendly in combination with renewable energy-based electricity, in which hydrogen is in-situ generated from electroreduction of water so that extra supply of H2 can be avoided. By optimizing the Cu catalyst to expose more active facets, preferential adsorption and hydrogenation of acetylene is facilitated against hydrogen adsorption and evolution. By using a microporous gas diffusion layer to promote mass transfer, a high Faradaic efficiency of 83.2% for ethylene production is achieved with a current density of 29 mA cm-2 at -0.6 V vs. RHE. In-situ spectroscopic characterizations combined with density functional theory calculations demonstrate that electron transfer from the Cu surface to adsorbed acetylene promotes the adsorption and hydrogenation of the acetylene, while suppressing the competitive hydrogen evolution reaction and facilitating ethylene desorption, thereby resulting in highly selective ethylene production via the electron-coupled proton transfer pathways. This process provides a green route for industrial production of C2H4 from C2H2 under mild conditions.

The work was published in Nature Communications on December 06 with a title of “Highly efficient ethylene production via electrocatalytic hydrogenation of acetylene under mild conditions”.

This work was supported by the National Natural Science Foundation of China, the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences, and Collaborative Innovation Center of Chemistry for Energy Materials (2011. iChEM). (Image and text by WANG Suheng and YU Liang)