Constructing Local Environment Of Electrocatalyst Active Sites And Performance Tuning

There are several remaining challenges for the hydrogen industry to go for large-scale commercial applied.First,considering the hydrogen production,the current major source of hydrogen in the world is still derived from fossil fuel reforming.But the hydrogen produced by this approach is not clean enough to be applied in the fuel cell.And further purification leads to a significant increase in costs.As an alternative,producing hydrogen by electrolysis of water is an environmentally-friendly and sustainable method.But,limited by the high value of precious metal catalysts and the unstable performance of electrolysis equipment,it is still too expensive to be commercial massively.Besides the challenges of the producing hydrogen,we need to address the severe problems in the use of fuel cells to convert hydrogen energy into electrochemical energy.The way of producing high-purity hydrogen by electrolysis of water is not suitable to be promoted in a large scale,so hydrogen in the industry is mainly supplied by reforming fossil fuels which is always containing some CO impurity.This situation leads to a big challenge in the poison tolerance of anodic catalyst in the fuel cell.How to use the hydrogen from reforming fossil fuels and avoid the poisoning of the impurity is another key issue in this field.On the other hand,the activity and stability problem of the cathodic catalyst also limits the commercialization of fuel cells.Among all the existed technology,researchers usually use precious metal as cathode catalyst.Due to the low kinetics of ORR,it required a large amount of Pt which results in a high cost for the fuel cells.To find a cheaper alternative of cathode catalyst has been a hot topic in the fuel cell's field.In brief,how to develop next-generation catalysts with high performance and high tolerance is the key to promote the development of fuel cells.In the past decades,researchers mainly focused on tuning the electronic structure and surface atomic structure of catalysts to improve the electrocatalytic performance and reaction selectivity.In this research,we attempted to develop a new approach for enhancing the activity or selectivity of electrocatalysts.Inspired by the enzyme reaction in the bio-system,precise construction of local active sites to regulate local reaction environment,modulate local hindered reaction and regulate the mass transfer process can optimize catalysts' performance and reaction selectivity.By constructing organic molecules building and strong absorbed water layer,we strengthen sterically hindered effect on precious metal catalyst surface to block poisonous species like CO and H₂S away from the catalyst' surface during the process of HOR,which significantly improves the precious metal catalysts' ability to tolerate poisonous species.Besides,by optimizing the nickel-based catalysts' ligand's electronic structure and introducing proton transfer sites to improve the proton-electron transferring process,and we improved the nickel-based catalysts' hydrogen evolution performance significantly.Last but not least,we have used a method of chemical selective modification to selectively modified different atom sites on the N-doped graphene ORR catalysts,and according to the change of catalysts' activity after blocking different sites by acetyl groups,we confirmed that the ortho-C atom of the pyridinic ring is the reactive site for ORR.This research has provided a new approach to designing electronic catalysts in the future,and new insight into how reaction environment impacts the catalysts'activity and selectivity.