Engaging in Curriculum Reform of Chinese Chemistry Graduate

Article pubs.acs.org/jchemeduc

Engaging in Curriculum Reform of Chinese Chemistry Graduate Education: An Example from a PhotocatalysisPrinciples and Applications Course Jiahai Ma* and Rongrong Guo School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049, China S Supporting Information *

ABSTRACT: As worldwide energy shortages and environmental degradation increase, along with steady increases in population, current science and technology are confronted with many challenges to successfully sustain our society. Among the existing promising choices, photocatalysis has been widely considered as a potential solution to energy and environment problems because of its double functions of producing H2 fuel directly from water and efficiently decomposing organic pollutants. This paper reports on the teaching experience of a graduate coursePhotocatalysis: Principles and Applicationsin the 2011−2012 spring term at University of Chinese Academy of Sciences (UCAS), mainly involving the teaching materials, literature discussion, and students’ feedback. During instruction, great efforts were made to introduce state-of-the-art research activities as well as related opportunities and challenges identified in top research papers, which are well received by the students. Feedback collected from the students was analyzed and is discussed, in order to improve this course accordingly. In addition, suggestions for potential yet non-expert instructors are provided, as well as ways to adapt the course for undergraduates. KEYWORDS: Upper-Division Undergraduate, Graduate Education/Research, Environmental Chemistry, Interdisciplinary/Multidisciplinary, Inquiry-Based/Discovery Learning, Free Radicals, Photochemistry, Materials Science, Nanotechnology, Oxidation/Reduction

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INTRODUCTION In different disciplines and courses, increasing attention has been paid to energy and environment issues that threaten our future. For example, green chemistry courses are popular and now offered in the undergraduate curricula of many universities. However, courses with a focus at the molecular or atomic level are still rare yet are strongly desired, especially by those hoping to address these issues. Catalysis is one of the core branches of chemistry and has changed and shaped the world. A century ago, people faced the crisis of the replacement of natural saltpeter; it was Haber’s invention that got “bread from air”, winning the battle of feeding ever-increasing populations.1 Comparably, how does chemistry help alleviate the urgent problems of our times such as energy shortages and environmental degradation? Many have pointed to photocatalysis. As one of the existing promising choices, photocatalysis has received much attention as a potential solution to the above problems because of to its double functions of producing H2 fuel directly from water and efficiently decomposing organic pollutants by the powerful, clean, and least expensive driving force from the sun. The University of Chinese Academy of Sciences (UCAS) shoulders the responsibility of educating thousands of graduates for the Chinese Academy of Sciences (CAS) every year, sustaining its more than 100 research institutes. In 2009, the management of the UCAS launched curriculum reform efforts.2 © 2013 American Chemical Society and Division of Chemical Education, Inc.

The new curricula added one new course of Photocatalysis: Principles and Applications into the physical chemistry division. This course was officially offered at the College of Chemistry and Chemical Engineering of UCAS during the 2011−2012 spring term. As a special graduate course on energy and environment problems, it pointed out opportunities and challenges for the graduates to think about ways of addressing these problems.

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COURSE ORGANIZATION

The Photocatalysis: Principles and Applications course met for 10 weeks in the spring term with two classes per week and 100 min per class (see Table 1 for the syllabus). The course attracted 27 students from 10 research institutes within CAS, covering nine subfields of chemistry, engineering, and material sciences. It is recommended that the students taking this course will have studied physical chemistry for no less than 120 academic hours; however, the knowledge background of the students was quite different, as cross-disciplinary learning is an important characteristic in UCAS. We used the discussion of recent literature as one major approach to teaching the course in addition to common lectures, with the teacher and students exploring together the opportunities and challenges in Published: November 18, 2013 206

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Table 1. Course Syllabus Outline for Photocatalysis: Principles and Applications Sections of the Course 1. Introduction 2. Photocatalytic oxidation of organics

3. Photocatalytic reduction 4. Dye-sensitization solar cells 5. Water splitting

Content (40 academic hours, 2 credits) Environment and energy challenges; Artificial photosynthesis; Designing photocatalytic systems 2.1Semiconductor photocatalysis: Principle of TiO2 photocatalysis; Effect of O2; Preparation and characterization of TiO2; Nonmetal doped TiO2 photocatalysis; Non-TiO2 semiconductor photocatalysis; Related industry applications and reactor design 2.2Metal ions and complexes photocatalysis: Photo-Fenton reaction; Iron-based metal complexes photocatalysis; Polyoxometalates photocatalysis Photocatalytic reduction of metal ions; Photocatalytic reduction of CO2; Photocatalytic reduction of halogenated hydrocarbons Nanocrystalline semiconductor electrodes; Sensitization dyes; Electrolyte Solid catalysts; Homogeneous catalysts

Table 2. Photocatalysis Literature Topics, References, and Characterizations Topics Solar cells Doping TiO2

Literature Citation 3 4−9

Effect of O2 (and organic synthesis) Effect of crystal morphology and facets New materials

10−14

Metal complex Self-cleaning Other

25 26, 27 28, 29

15−18 19−24

Opportunities/Challenges Improving light-to-electric conversion efficiency; Designing novel sensitization dye Reveal accurate doping mechanism; Achieving excellent visible light response; Improving thermal stability; Avoiding carrier-recombination Stronger in situ, online analytical methods; Unambiguous and intricate experiments design; Demonstrate the generality of mechanism; Novel mechanism is used to efficient synthesis Note and explain well the consistence and difference of reported results; More simple synthesis method Achieving excellent visible light response; Improving quantum yield; Targeting overall water splitting; Involvement of theoretical calculation; Simple, economic, and industry-scale fabrication Ultrahigh turnover number; Revealing detailed reaction mechanism Successful applications in daily life Systematically compare the efficiency of various photocatalysts; Expanding the scope of photocatalysis applications (e.g., reduction of CO2)

and students likely made to learn by rote), the literature discussion was the most important and major part of the class in keeping with a recent editorial in this Journal emphasizing that “active methods are better than passive ones, that knowledge is built, not simply transferred”.30 Indeed, these research papers were shared with and quite appreciated by the students (see the feedback discussed below). This activity greatly enriched the students’ scientific experience by getting them actively engaged in learning and debating specific issues related to the course materials. Finally, students learned that no paper was perfect, based on their close readings and profound discussions. The students were treated as researchers, in a sense. Most of the literature sources were provided by the teacher, while some were selected by the students. Generally speaking, students preferred to choose papers closely related to their individual research project from their advisors while focusing less on the academic importance of the paper itself. Hence, in future course offerings, the teacher will select all the papers. Worthy of note, students tended to lecture on papers without involving any supporting information (SI) despite the fact the SI for any given paper was quite important; students will be required to include the SI in future course offerings.

photocatalysis found while studying and discussing the literature. Teaching Materials

Today, educators face the challenge of bridging gaps between delivering basic knowledge and truly achieving graduate education goals, namely, to cultivate qualified future researchers. Concerning this, the teaching philosophy in designing this course was to strongly increase the relevance of this course to current trends in academia, while maintaining the solid concepts for solving energy and environment problems. Teaching materials are the most important elements for a course; Table 1 indicates the content and sequence of this course. We wanted to teach the full spectrum of research skills through the route of design, synthesis, mechanism, and application of a catalyst. The course first emphasized the energy and environment challenges. We focused mainly on semiconductor photocatalysis while introducing homogeneous photocatalysis (metal complexes as catalysts). For applications, dye-sensitization solar cells were briefly introduced (Table 2; ref 3), while water splitting was heavily discussed owing to its importance, and degradation of organic pollutants and chemical synthesis were included, too. Second, for most of the content in the sections, the traditional lecture-based format was abandoned, in consideration that this was a small-scale class with relatively plentiful academic hours. Instead, recent literature works3−29 were discussed in class (Table 2) with each student taking turns to present one article to the rest of the class. Students therefore were well prepared for the class; further, they were allowed to select the literature freely. In contrast to the majority of chemistry classes in China (lecture-based and teacher-centered,

Literature Discussion

In Section 1 of the course, the energy and environmental problems people are facing and Haber’s story were introduced to emphasize the potential role of photocatalysis and inspire the students’ interest in this topic.31 Further, the Fujishima−Honda effect and the original two-page paper on it were used to begin the whole photocatalysis course journey.32 Then, the selected 27 papers3−29 were divided into four major topicsdoping TiO2, effect of O2, effect of crystal morphology and facets, and 207

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orgagocatalysis,39 as well as adding related topics and updating the literature table, as new and important papers will have been produced. As a good supplement to regular classroom education, the UCAS has a summer term that attracts many students.2 In previous summers, some prominent professors were invited to present the topics in the Environmental Catalysis series, including Jincai Zhao. Students highly admire these lectures. In the future, more photocatalysis-related lectures will be included in the summer term.

new materialsand other four minor topics. (See the Supporting Information for an expanded version of Table 2.) For the topic of doping TiO2, metal doping was no longer popular and had been greatly debated with regard to the positive and negative effects; thus, successful nonmetal doping was chosen. N-doped TiO2 had achieved great success (Table 2; ref 4) and stimulated ensuing publications. Kahn’s paper (Table 2; ref 5) was on C-doped TiO2, and it was used to familiarize students with the comments and responses from the related debates.33−35 Last but not least, B-doped TiO2 (Table 2; ref 6) was selected; even this solo paper stimulated a series of ensuing insightful studies by other research groups.36,37 Selfcleaning is yet another important application of photocatalysis; two papers from one Chinese research group were used to explore this (Table 2; refs 26 and 27). The greenest and least costly oxidant of O2 is the most significant attraction of photocatalysis; thus, the effect of O2 topic was included in the reaction mechanism study. Effect of crystal morphology and facets is the current hot topic of photocatalysis, for which four interesting studies were used (Table 2; refs 15−18) and the students were encouraged to compare these reported results and find existing consistencies and inconsistencies. The students were also presented with a series of novel photocatalysts besides TiO2-based catalysts under the topic of new materials, and most of these catalysts work efficiently under visible irradiation. For metal complexes analogous to enzymes, only one paper was selected (Table 2, ref 25); thus, the students were encouraged to find and read related papers by themselves. Generally, these selected papers were highly cited and highly visible to academic community. Some were classics and had been cited over thousands of times, while some were recently published. For recent papers,10,11,13,14,27 some were cover articles published in outstanding journals such as Angewandte Chemie International Edition and ChemistryA European Journal. Many Chinese researchers’ papers were specially selected to encourage the students, and it was noted that several papers were selected from the Jincai Zhao group (Key Laboratory of Photochemistry, Institute of Chemistry, CAS). This group is dedicated to studies on the photocatalytic degradation of organic pollutants and related oxidation reaction mechanism. From their work, we understood the status of the current photocatalysis as well as how it advances understanding of the reaction at the molecular level. More importantly, detailed experiment designs, comments, and responses pertaining to these papersusually unseen development of the text of the articlewere also presented to the students, kindly provided by Zhao’s group. The reviewers’ comments are invaluable resources for graduates to critically scrutinize the papers and learn from experts the way to examine scientific problems. In addition, from these selected papers, we could see China’s significant contributions in the field of photocatalysis; indeed, Chinese researchers published fewer than 200 papers in 1990− 1999 but more than 5000 papers in the next decade and even over 3000 in the last two years alone.38 China is becoming more competent in this field, which demonstrates that more opportunities and challenges in the field are available. (Getting students more involved in this field was another objective of the course.) For the topic of “other”, the current selected papers were on polyoxometalate (POM) (Table 2, refs 28 and 29). In future course offerings, we would like to introduce photoredox

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STUDENTS’ FEEDBACK Near the end of the course, the instructor collected feedback from 25 students in the class. A summary of that feedback is provided below. Positive Comments

Students provided some comments indicating the aspects of the course they found helpful and satisfying (the comments are aggregated by topic and translated from Chinese by the authors): The ability to benefit from literature reading was greatly improved; [students were] acquainted with the sense of scientific research. (N = 13) Open discussion engaged [students’] interest and passion for studying and developed [students’] lecture ability. (N = 7) The teaching material was closely related to real research. (N = 6) The course broadened [students’] view of the material. (N = 4) Homework and after-class reading materials were appropriately assigned. (N = 3) The lecture and exam format was novel. (N = 2) Comments on Inadequacies

Students provided some comments indicating the aspects of the course they found unsatisfactory (the comments are aggregated by topic and translated from Chinese by the authors): The basic knowledge [students had entering the course] was not enough, so it is hard to understand. (N = 1) The theoretical content was not enough. (N = 1) The course was too advanced to understand, and the range of material covered was too large. (N = 1) The course material was not broad enough. (N = 1) Summary and Further Action

The feedback opinions generally indicated that the students like to present and share original research papers in class, and that class discussion of the papers inspires the students. Further, students read and think about the material outside of class when they believe it is rewarding; in fact, the students were so ambitious that they were eager to start their own research as soon as possible. Compared with another large-scale class of organic structure analysis at the same institution,2 student participation in the class was more active and some of the students spent more time on the course material outside of class. What did the students get out of this? This course made the students “sense” the research and read literature carefully. Especially in discussions, the students read the articles prudently, reviewing the data, the experimental design, and generally the ways to see whether the energy or environmental 208

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Table 3. A “Toolbox” for Teaching Photocatalysis Teaching Content The origin of and driving force for photocatalysis Semiconductors Synthesis Characterization Reaction mechanisms Theory calculations

Knowledge Needed Energy and environmental issues Band gap; Crystal phase, facet, and size Sol−gel route; Spin coating Friction force microscopy (FFM); Atom force microscopy (AFM); Scanning electron microscope (SEM); Transmission electron microscopy (TEM); Diffuse reflectance UV−vis spectroscopy; X-ray photoelectron spectroscopy (XPS); X-ray diffraction (XRD); Scherrer formula; BET surface area; Dynamic light scattering (DLS) Capillary effect; Reactive oxygen species (ROS); Electron paramagnetic resonance (EPR); Resonance Raman; Diffuse reflectance FTIR (DRIFTS); Kinetic isotope effect (KIE) Density of states (DOS); Density functional theory (DFT)

From a general point of view, how can this course be improved in the future? First of all, the class will be subjected to dynamic adjustments for its sustainable development. Besides updating the teaching materials, interdisciplinary collaboration is also expected. Joint teaching promotes designing and implementing better courses by drawing on the combined expertise.40 Future course offerings would try to include one or two faculty members from different disciplines within the departments of materials science and environmental science to lecture two class hours to foster interdisciplinary dialogue and thinking. More broadly speaking, in addition to maintaining incremental course development (such as green chemistry) that we are currently pursuing, we will pursue interdisciplinary education collaboration of different forms at different institutions as an important part of fully realizing green technology’s transformative potential, including the important technology of photocatalysis for solving environmental and energy problems.

concerns were potentially integrated. In addition to the related chemical concepts or knowledge, the students learned: (i) why the scientists did such experiments; (ii) what implications and further questions the literature brought to them; (iii) whether the reported results could be worth further investigation and how to do it; and (iv) whether the reported mechanism was universal, and what other conclusions could be made. This course helped students understand the actual research and writing process in depth, which was one of the goals of the course. With students’ feedback in mind, future offerings of this course will provide more basic theory of catalysis and semiconductors.

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FLEXIBILITY OF THE COURSE The course syllabus (Table 1) and the literature references (Table 2) would be useful for a potential, yet non-expert, instructor to prepare related topics in physical chemistry courses or a seminar course. Further, for a more general audience of undergraduate physical chemistry instructors who are not necessarily expert in photochemistry or others in related disciplines, a readily available “toolbox” (Table 3) was developed. From the table, potential instructors could easily pick up the “tool” or “tools” of related knowledge and prepare for teaching students more effectively for better learning results. Moreover, due to its interdisciplinary nature, this course should be more flexible for other related majors, such as materials science, environmental science, and engineering. On the basis of instructors’ careful selection of topics, literature sources, and corresponding supplementary materials, the course could be adapted to an upper-level undergraduate course by focusing more on foundation materials and less on some of the discussions of the frontiers of the field.

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ASSOCIATED CONTENT

S Supporting Information *

An expanded version of Table 2 showing the affiliations and geographic distribution of the corresponding authors of the articles used in the course.3−29 This material is available via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank all the students taking the 2011−2012 class of Photocatalysis: Principles and Applications, especially those who gave valuable suggestions for the class. We also thank the reviewers for their valuable suggestions. J. Ma thanks the NSFC (Nos. 21007089 and 21377126) and the SRF for ROCS, SEM for supporting his research. Special acknowledgment is expressed to Leilei Zhang and Min Jia for their kind and valuable input on English language refinement.

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IMPLICATIONS The aim of the course was to lecture on the overarching idea of how to successfully apply photocatalysis to real-world problems, attracting more knowledgeable, prepared graduate students (future researchers) into this promising field. The course ended with the acknowledgment that “although much has been done, more efforts are needed”. Inspiring the graduate students is complex and challenging but rewarding work. Hopefully, this approach will be effective: a similar exhortation was given during a two-hour talk on photocatalysis (materials mainly collected from the first and last class of the course) for selected high school chemistry teachers (about 40) from China’s key high schools in a summer session, with encouraging and positive responses received.

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REFERENCES

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