From a student to a professor: an after-the-paper story of 2D Si for CO2 catalysis

One year ago, we had the honor to tell a story of 2D Si for CO2 photocatalysis. One year later, I accepted the invitation to again share my personal story. I have been fortunate to experience the joy of learning, collaborating, and teaching, during this transition year from a student to a professor.

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The beauty of being a professor is one is a student for lifelong learning.” Said by my previous PhD supervisor Prof. Geoffrey Ozin, in a recent email replying my short narrative of my current life being a Professor (research stream) at Zhejiang University. His proverb-like comment is particularly true for me, as I am a young and new PI trying to learn how to accommodate myself to the competitive academic environment in China, and I am grateful that he is still always available whenever I want to learn from him. 2019 was the last year when I worked in the Ozin group (Figure 1) at University of Toronto, Canada, as a postdoc fellow after obtaining the PhD degree from the same university. Right before I left for China, we discovered that through tuning the chemistry of two-dimensional silicon, the location of Ni nanoparticles being either interior or exterior to the Si nanosheets could be determined, which ultimately influenced the performance of catalytic CO2 methanation reaction. This work was finalized into a publication in Nature Communications (https://www.nature.com/articles/s41467-019-10464-x), and was introduced in the Nature Research Community (https://go.nature.com/31xhdG8). The story however did not just end there.

Figure 1. A photo of the Ozin group, in which I spent the happiest time of my life, taken in 2018.

    The collaboration between the team members who contributed to the mentioned work has never stopped. Prof. Xiaoliang Yan, who co-first authored this work published in Nature Comm., one day serendipitously discovered that the Si nanosheets powder I synthesized in the Ozin lab started to literally BURN, when just put in a furnace that was still warm after someone else’s experimentLuckily the flame was confined within a small glass vial and it only lasted for seconds, so we didn’t have to report any fire case. Recall it was silicon, not powder of metal or charcoal, so the fact that it could be ignited and could turn black afterwards was mysterious. This serendipity drove us to again investigate together why the Si nanosheets could be ignited and what reactions and transformations occurred, although I already went back to China. The original team “reunited” in the online virtual space for brainstorming and allocation of tasks. One of the key authors Dr Wu Wang, who had also returned to China after graduating from Karlsruher Institut für Technologie (KIT), revealed using advanced STEM analysis that nanorods were formed from the Si nanosheets after the ignition, and Ni-containing nanoparticles were located at the head of these nanorods (Figure 2), sourced from Ni nitrate precursor for the impregnation method. This 1D/2D hybrid morphology happens to resemble the Si nanorods grown on a substrate from the well-known vapor-liquid-solid (VLS) method, a well-studied field by my current institution: the State Key Lab of Silicon Materials. However, there was no external SiH4 vapor usually required as the Si source, which differs our case to the traditional systems. Through brainstorming and further X-ray spectroscopy analyses with Prof. Ozin and Dr Paul Duschesne (now an assistant professor in Queens University, Canada), we unraveled the mysteries of the novel growth reaction pathway, and the nanorod/nanoparticle compositions, which were summarized into a recent article published in Small (https://doi.org/10.1002/smll.202001435). Every author has made invaluable contribution towards this complete story with scientific excellence, and I have truly sensed the endless power of a great team. At the time of writing this story, I am still in contact with these lovely people on daily basis working on more collaborative studies.

Figure 2. The Fast reaction process and the morphology of the resultant hybrid 1D/2D materials. a) A thermographic image of the sample vial right after vacuum drying the precursors. b) Schematic illustration of igniting the solid–solid precursors. c) Pictures of the glass vial before and after the reaction. d) Selected snapshots of the FSS reaction period. STEM image and EDX mappings of two representative areas in e) Ni/SiXNS and f) Co/SiXNS. The scale bars of STEM in (e) and (f) are 200 and 100 nm, respectively, and are 20 nm in the EDX mappings. Reproduced with permission (https://doi.org/10.1002/smll.202001435). Copyright 2020, Wiley‐VCH

    These discoveries have encouraged me to continue working on the “Nanosilicon Samurai”, and have helped me secure funding so I could support and teach my own graduate students. The valuable experience in publishing with Springer Nature and those elite journals has been one of the great things I have felt like sharing with my students. I am teaching them what I have learned during my PhD study: focusing on the innovation, being scrupulous about the results, percolating over and over the interpretations, maintaining creative and aesthetical standards in graphics, which are some vital factors towards a high-impact work. While teaching, I am still learning, both from my lifetime mentor Prof. Ozin, and from my current colleagues, who are expertised in the hardcore semiconductor physics and Si material science. Moreover, I learn from the students that I teach, who have fresh memories of the most updated knowledge from higher education. I was amazed by their solid mathematic and computer skills. I really appreciate that the leader of Silicon Research Group Prof. Deren Yang has embraced my participation of research in this group (Figure 3), and has supported me unconditionally to collaborate and learn freely during the past year.

Figure 3. A photo of the PIs and staffs in the Silicon Research Group, in which I am doing exciting collaborative works on 2D Si and nano-silicon, taken in 2020.

    The publications with Springer Nature might not be the only reason for all these exciting opportunities I have fortunately acquired in the past year, but they certainly have encouraged me to embrace the joy of learning, collaborating, and teaching, which I find particularly beneficial for my career in this transitional year. What’s next? From a nanochemistry group to a semiconductor materials group, I migrated from a fruitful land to a gold mine, and I anticipate that I could be a bridge to link these two important areas, by working on the innovative and functional nanosilicon materials. I will continue to “stay hungry and stay foolish”, as a fresh professor, but also a lifelong student.

Wei Sun

Professor, Zhejiang University

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