The Chinese University of Science and Technology is developing a highly active electrocatalytic oxygen reduction reaction based on the elements of the main group S zone
Electrocatalytic oxygen reduction (ORR) is an important link in energy conversion and storage. Under the guidance of catalytic d-band center theory, the design and preparation of current electrocatalysts are developing from precious metals to transition metal-based materials to reduce The cost of energy conversion. Generally, the main group metal elements are considered to be less active due to the lack of suitable half-full orbitals for multi-electron catalysis due to their own non-localized outer electrons. Therefore, the materials based on the main group s zone metals are used as ORR electrocatalysts. No report yet. Recently, Professor Chen Qianwang, a professor at the National Research Center for Microscale Physical Sciences and the School of Materials Science and Engineering, Hefei University of Science and Technology of China, has made progress in the development of highly efficient ORR reaction catalysts based on metals in the main group s zone. In the experiment, a carbon-based catalyst containing magnesium (Mg) cofactor was synthesized, and the metal Mg in the main group s zone was developed into an ORR electrocatalyst with comparable precious metals. The research results were published in Nature Communications on February 18th.
The catalytic d-band center theory holds that the transition metal d-orbit center is linearly related to the adsorption free energy of reactive species on the metal surface, and has been used to guide the design of transition metal catalysts. However, the interaction between the delocalized s band of the main group s zone metal and the reaction intermediate often leads to too strong or too weak adsorption, so it is not a good catalyst. However, in nature, coenzyme factors centered on Mg (such as DNA polymerase and hexokinase) show high activity in some biochemical reactions. This natural method of adjusting the energy band of the central atom through the feedback bond between the metal and the coordination atom provides an idea for the experimental design of the main group metal catalyst. Through theoretical calculations, changing the coordination number of nitrogen (N) atoms to adjust the energy band structure of the central metal atom, and then screening out the structure of Mg-N2 has the most suitable reaction adsorption energy, the performance is close to the precious metal platinum. The experimental design synthesized a new Mg-based MOF. After high-temperature pyrolysis, some Mg atoms were riveted on the graphene-like carbon substrate by N rivets to form a Mg-N coordination structure catalyst. Its alkaline ORR activity exceeds commercial platinum carbon, the half-wave potential reaches 910mV, and has excellent stability, no attenuation after 5000 cycles. In addition, in acidic ORR, this material also has high activity and good stability with a half-wave potential of 790mV. Through reasonable catalyst design and electronic structure control, the catalyst prepared based on the main group s zone metal can also be comparable to the transition metal catalyst, which provides a new idea for the design of the catalyst.
Liu Shuai, Ph.D. student of Hefei National Research Center for Microscale Physical Sciences, is the first author of the paper, and Chen Qianwang is the corresponding author. The research was supported by the National Natural Science Foundation of China.
Figure: Reactivity calculation and results of the metal cofactor structure model. (A) Four different N-coordinated metal (Mg, Al and Ca) cofactor models. (Bc) The linear relationship between reaction intermediate species in ORR. (D) Reactive volcano diagram of metal cofactors. (E) Comparison of the activity of selected high-activity metal cofactors with transition metal cofactors.
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