It is well known that hydrogen has advantages of extremely high energy density and low environmental impact. It’s significant for developing and using the cleaned energy. The processes of electrocatalytic hydrogen evolution reaction (HER, 2H⁺+ 2e^- → H₂ ) is a cathode surface reaction which play an important role in hydrogen evolution of reversible hydrogen fuel cells and other technologies , so it is considered as a kind of cleaned and renewable energy technology receiving widespread attention. Now the bottleneck of this technology is how to design and develop electrocatalysts with higher activity and lower cost. Despite the rapid development on alternative materials in recent years, Pt is still the most efficient and stalest material for various electrocatalytic reactions, but it is with high cost. Reducing the Pt usage and boosting the electrocatalytic performance are always the ultimate goals for electrocatalyst design to achieve cost-effective, high-efficiency hydrogen production. From this point of view, to lower the material cost and enhance the electrocatalytic performance is the major trend to develop Pt-based alloy materials through various synthetic methods. Recently, iChEM researcher, Prof. Yujie Xiong’s team in University of Science and Technology, reported the synthesis of PtFeCo alloy nanostructures in a TriStar shape with tunable Fe and Co contents toward the HER application with high activity and low Pt usage. The result was published in Advanced Materials (2016, 28, 2077), and highlighted in Chinese news website Materials Views China of Wiley (http://www.materialsviewschina.com/2016/03/platinum-base-alloy-nano-structure-three-pointed-star-regulating-performance-of-catalyst-for-new-thinking/).The co-first author of the paper are Ms. Nana Du, Senior Engineer, Dr. Chengming Wang and Dr. Xijun Wang.

The past research indicates that the key of enhancing the electrocatalytic activity of materials is to tune electronic and surface structures. So the big challenge of designing and preparing materials is to tune the two parameters synchronously. In recent years, Xiong’s team proposed a interface charge polarization mechanism for catalyst designing, which based of atomically controlling interface formation and tuning amounts of active sites and activity by controlling the dimension of interface (J. Am. Chem. Soc. 2014, 136, 14650; Angew. Chem. Int. Ed. 2014, 53, 12120; Angew. Chem. Int. Ed. 2015, 54, 14810). In this work, researchers generalized the atomic charge polarization mechanisms to alloy system and realized adjustable electronic structures by tuning the electron density of Pt active site. They for the first time developed a synthetic approach to tri-metallic PtFeCo alloy nanostructures with precise controllable compositions and in a unique TriStar shape, which has good HER performance. In the meantime, it provides a great platform for investigating the composition-dependent HER performance. The HER performance of these TriStar nanostructures turns out to have a strong correlation with the chemical compositions, to which interatomic charge polarization and d electron couplings may both make contributions. The collaborator Jun Jiang’s team calculates the projected density of states (PDOS) of Pt d orbitals in the three models. They suggest that the incorporation of Co into the PtFe lattice induces charge polarization between atoms and can tune electron density of atom and the d-band center of Pt atom meanwhile to enhance the activity of active sites. Based on this point, researchers establish the quantitative structure-activity relationship between alloy composition and HER performance.

Researchers synthesize a Pt₈₁Fe₂₈Co₁₀ Tristar nanostructures with current density up to 1325 mA cm^-2 at potential of −400 mV, which is 4 times than commercial Pt/C catalyst and much better than other Pt-based catalyst. Meantime, the stability of Pt₈₁Fe₂₈Co₁₀ get improvement compared with other catalyst. The PtFeCo TriStar nanostructures well combines the surface and electronic structures design with the composition engineering, and they provide fresh insights into rationally designing the alloy electrocatalysts with low-cost and high-performance.

This work was financially supported by the 973 Program, the NSFC, the Anhui Provincial Natural Science Foundation, the Recruitment Program of Global Experts, the CAS Hundred Talent Program, the Hefei Science Center (CAS) Funds for Users with Potential, and the Fundamental Research Funds for the Central Universities. (School of Chemistry and Materials Science, Hefei National Laboratory for Physical Sciences at the Microscale, iChEM, Hefei Science Center CAS (2015HSC-UP012), Research Department)

http://onlinelibrary.wiley.com/doi/10.1002/adma.201504785/abstract