Dalian Chemical Institute realizes high-purity hydrogen by electrochemical water vapor shift at room temperature

Recently, the team of Deng Dehui, a researcher at the State Key Laboratory of Catalysis Fundamentals, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, proposed and implemented for the first time a new strategy for preparing high-purity hydrogen (> 99.99%) with high energy efficiency: room temperature electrochemical water vapor shift (EWGS) . Related results are published in full text in "Nat. Commun."

Hydrogen energy is regarded as the clean energy with the most development potential in the 21st century. At present, the water vapor shift (WGS) reaction (CO + H2O → H2 + CO2) is the main method for industrial large-scale production of hydrogen. But the WGS process usually needs to be carried out under the conditions of high temperature (180 ° C-250 ° C) and high pressure (1.0-6.0MPa). In addition to the harsh reaction conditions, the hydrogen produced by the WGS reaction often contains about 1% -10% of CO residues and the reaction products CO2 and CH4, etc., and requires further separation and purification before it can be used in downstream applications. Therefore, the development of more economical and environmentally friendly methods to directly produce high-purity hydrogen under mild conditions is an urgent need for the development of hydrogen energy, but it is also extremely challenging.

After a long period of exploration, the Deng Dehui team combined the principle of electrochemical reaction to skillfully split the redox reaction of WGS into two half-reactions separated from each other. For the first time, an electrochemical method capable of directly preparing high-purity hydrogen at normal temperature and pressure was proposed. Water vapor transformation concept. In the EWGS reaction, CO oxidizes at the anode, and the generated CO2 further reacts with the electrolyte KOH to form potassium carbonate, which avoids CO2 emissions; at the same time, water is directly reduced at the cathode to generate high-purity hydrogen. The anode and cathode are separated by an anion exchange membrane, which keeps the ion balance of the solution while separating the products of the two electrodes. Therefore, in principle, the process of separating and purifying hydrogen in traditional WGS is avoided. Through the optimization of the catalyst design and electrode structure, the reaction achieves the preparation of 99.99% high-purity hydrogen under normal temperature and pressure conditions and achieves a hydrogen production faraday efficiency close to 100%. The initial anode potential of the optimized PtCu catalyst in the EWGS reaction is reduced to close to 0V, which is significantly lower than the theoretical anode potential of electrolyzed water of 1.23V; at 0.6V, the LSV current density reaches 70mA / cm2, which is higher than the commercial Pt / C catalyst The activity of the catalyst has increased by more than 12 times; the catalyst can still maintain high activity after 475 hours of stability test. On this basis, the team collaborated with Dalian Institute of Chemical Researcher Su Haiyan and others. Through theoretical calculations, it was found that the introduction of Cu weakened the adsorption of CO on Pt and effectively avoided the poisoning of the catalyst, thereby achieving the catalyst in EWGS. High activity and high stability. Compared with traditional WGS, EWGS is a completely different and efficient catalytic process that can be carried out at room temperature and atmospheric pressure, which provides a new idea for the production of high-purity hydrogen with low energy consumption.

The above research received the National Ministry of Science and Technology Key R & D Program, the National Natural Science Foundation of China, the Chinese Academy of Sciences Frontier Science Key Research Project, the Chinese Academy of Sciences Clean Energy Innovation Research Institute Cooperation Fund Project, the Ministry of Education Energy Material Chemistry Collaborative Innovation Center (2011 · iChEM) and post-doctoral innovative talents Support the program's funding.

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