Our research group focuses on the important electrocatalytic reactions in the field of clean energy conversion, such as ORR, OER, HER, and CO2RR. At present, the reaction mechanism of relevant electrocatalytic reactions is still not clear enough, and the evolution of active centers in the electrocatalytic process also needs to be elucidated. Based on catalyst design, our research group conducts in-depth research around reaction pathways, adsorption states, and evolution of active centers. The main research content includes：
The key issues in the study of electrocatalytic mechanisms
（1）Research on electrocatalytic reaction pathways
Electrocatalytic reactions, which often involve multiple reaction intermediates and complex proton-coupled electron transfer steps, suffer from sluggish kinetics, resulting in insufficient activity. Therefore, studying on the pathways of catalytic reactions and lowering the energy barrier of the rate-determining-step is an important idea for designing high-performance catalysts. (1) We realized the ORR dissociation path by reducing the O coverage (ΘO) on the catalyst surface, which could promote the adsorption of O2 and weaken the binding energy of oxygen intermediates, facilitate the rapid dissociation of O2 and desorption of oxygen intermediates. (2) We designed Mo-Ce oxide carriers, which can promote the in-situ conversion of Co2+-O to Co3+-O in CoSA-MoCeOx@BCT at low voltage which effectively regulates the lattice oxygen activity of the catalyst with abundant oxygen vacancies, generating a dual-metal-site LOM pathway to break the scaling relations and significantly enhancing the inherent OER activity. (3) The similar adsorption energies of multiple reaction intermediates in electrochemical CO2 reduction lead to poor catalyst selectivity and wide product distribution. Therefore, we initially screened one or more suitable metals as alloy catalysts, and rationally designed catalysts with different alloy ratios or structures in combination with theoretical calculations to explore the possible reaction paths in electrocatalytic reactions. Representative work: Nat. Catal. 2024, https://doi.org/10.1038/s41929-024-01167-8; Energy Environ. Sci., 2024,17, 3088; Appl. Catal. B: Environ. 2021, 289, 119783
(2) Research on catalytic activity based on free energy of adsorption state
During the catalytic reaction, the adsorption strength between the reaction intermediate and the substrate catalyst directly affects the catalytic activity and selectivity. According to Sabatier's principle, too strong adsorption strength is detrimental to the subsequent catalytic reaction, and too weak adsorption strength leads to lower catalytic performance. Catalysts with moderate adsorption strengths facilitate efficient catalytic reaction processes. Therefore, studying on the strength of the adsorption state of the intermediates is an important descriptor of the catalytic performance of the reaction. (1) Investigating catalyst constitutive relationships through stress modulation: We introduced stress effects by doping heterogeneous elements in intermetallic compounds, plotting volcano type curves between activity and stress-strain, And we found that catalysts located at the top of the volcano diagrams had optimal activity. It is revealed that proper regulation of the stress-strain on the catalyst surface can optimize the adsorption energy between the catalyst-intermediates and achieve efficient catalyst design. (2) Alteration of adsorption strength by catalyst structural design: Since the affinity of O-based adsorbates for Fe is higher than that for Ni, substitution with Fe on the NiOOH surface will enhance the OER activity. Upon doping S into NixFe1-xOOH, the surface S residues will significantly reduce the free energy gap for adsorption of intermediates O* and OH* on the Fe site, thus lowering the OER overpotential of the catalyst. Representative work: J. Am. Chem. Soc. 2024, 146, 2033.; Angew. Chem. Int. Ed. 2023, 62, e202302134.；Adv. Energy Mater., 2020, 10, 2000179.; Adv. Energy Mater., 2019, 9, 1803771.; Angew. Chem. Int. Ed., 2019, 58, 15471. ；Adv. Mater., 2018, 21, 1800757.
（3）Research on evolution of active centers based on in-situ characterization
Due to potential changes and special solution environments, the geometry and electronic structure of catalysts may be changed during electrocatalysis, hindering the understanding of the actual catalytic sites of catalytic reactions. Therefore, we are committed to using in-situ characterization to observe the evolution of catalysts during electrocatalysis, which helps to gain a deeper understanding of the constitutive relationships in electrocatalytic reactions as well as the corrosion mechanisms of catalysts. (1) We used in-situ synchrotron radiation to study the in-situ structural evolution of ultrathin Pd-based multimetallic nanowires catalysts during the ORR process, and the results show that the Pd-Pd bond length/strain changes dynamically with the applied potential, realizing the enhancement of the catalyst ORR activity. Meanwhile, we verified the relationship between the electronic structure of the catalyst and the high activity in combination with theoretical calculations. (2) We modulated the metal-ligand binding constants to prepare highly stable Fe-N4/C catalysts and weakly stable Fe-N2~3/C catalysts. Quasi-in-situ EXAFS showed that the Fe-N4/C catalysts were able to be able to maintain structural stability after stability testing, while the Fe-N2~3/C catalysts experienced structural collapse. (3) For the in-situ evolution of the active sites during oxygen precipitation, in-situ synchrotron radiation and in-situ Raman characterization were used to analyze the valence state and local coordination structure of the active sites, so as to derive the correlation between the in-situ transformation of the valence state and the local coordination environment of the active sites and the activity of the oxygen precipitation reaction as well as the pathway of the oxygen precipitation reaction during the oxygen precipitation process. Representative work: Nat. Catal. 2024, DOI: 10.1038/s41929-024-01167-8; Energy Environ. Sci., 2024,17, 3088; Adv. Mater. 2021, 33, 2006613.
