与Al Bard的对话,ACS Energy Letters

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与Al Bard的对话
ACS Energy Letters ( IF 19.3 ) Pub Date : 2017-07-13 00:00:00 , DOI: 10.1021/acsenergylett.7b00566
Prashant V. Kamat ₁

Affiliation

艾伦·巴德生于1933年12月18日在纽约市，长大后就读于该校的公立学校，包括布朗克斯科学高中（1948–1951）。他曾就读纽约市立大学城市学院（CCNY）（1955年获得学士学位）和哈佛大学（1956年文学硕士，1958年获得博士学位）。Bard博士于1958年加入德克萨斯大学奥斯汀分校（UT）的教职，并在这里度过了整个职业生涯。自1985年以来，他一直担任UT的Hackerman-Welch Regents主席。1973年，他在让·米歇尔·萨万特（Jean-MichelSavéant）在巴黎的CNRS实验室休假，并于1977年在加利福尼亚理工学院的一个学期度过，当时他是谢尔曼（Sherman）米尔斯飞兆半导体学者。1987年春季，他还是康奈尔大学的贝克讲师，并于1988年在哈佛大学担任罗伯特·伯恩斯·伍德沃德的客座教授。他曾与99位博士一起担任导师和合作者。学生，18名MS学生，200多名博士后研究员以及众多访问科学家。他发表了988篇经同行评审的研究论文，75本书章节和其他出版物，并且获得了23多项专利。他撰写了三本书：化学平衡（1966），《电化学方法-基本原理和应用》（1980年，第二版，2001年，LR Faulkner）和《集成化学系统：纳米技术的化学方法》（1994年）。他曾担任1982-2001年《美国化学会杂志》主编。他的许多奖项包括ACS Priestley奖章（2002），Welch Foundation化学奖（2004），Wolf Foundation奖（2008），2011年国家科学奖（2011）和Enrico Fermi奖（2013）。他的研究兴趣涉及将电化学方法应用于化学问题的研究，包括扫描电化学显微镜，电化学发光和光电化学的研究。现代电化学之父是德州大学奥斯汀分校化学教授Allen（Al）J. Bard经常使用的术语。在将近五十年的时间里，他在确定能源研究的关键领域方面一直具有很高的远见（图1）。从基础电化学到电化学发光，从电极上的光诱导过程到染料敏化，从半导体颗粒光催化到单晶半导体光电化学，他从1970年代就做出了开创性的贡献。他已经培养了近50年的光电化学技术，并培养了几代学生和博士后研究人员，这些人已经成为成功的能源研究人员。他的终生研究贡献已获得美国化学学会的最高荣誉普里斯特利奖章的认可。2011年，他还获得了巴拉克·奥巴马（Barak Obama）总统颁发的国家科学奖章。图1.最近一次访问德克萨斯大学奥斯汀分校的过程中，艾伦·巴德（Allen J. Bard）教授与他进行了交谈。（照片由P. Kamat提供）。随着1970年代第一次石油危机的出现，阿尔·巴德（Al Bard）教授主动从事可再生能源研究，并发表了一系列与半导体光电化学和光催化有关的论文。这些早期论文提供了将光能光电化学/光催化转化为电能或化学能的基本原理。无论是新型太阳能电池的设计还是水分解和一氧化碳的储能装置随着1970年代第一次石油危机的出现，阿尔·巴德（Al Bard）教授主动从事可再生能源研究，并发表了一系列与半导体光电化学和光催化有关的论文。这些早期论文提供了将光能光电化学/光催化转化为电能或化学能的基本原理。无论是新型太阳能电池的设计还是水分解和一氧化碳的储能装置随着1970年代第一次石油危机的出现，阿尔·巴德（Al Bard）教授主动从事可再生能源研究，并发表了一系列与半导体光电化学和光催化有关的论文。这些早期论文提供了将光能光电化学/光催化转化为电能或化学能的基本原理。无论是新型太阳能电池的设计还是水分解和一氧化碳的储能装置_归纳为2，我们发现他发表的著作在进行现代能源研究时具有很高的参考价值（图2）。以下对话提供了对艾伦·巴德教授的远见世界的一些见解。图2. Bard教授在半导体光电化学和光催化领域的重要贡献为现代能源研究提供了基础。EL（ACS能源快报）：在您职业生涯的早期，您如何对光电化学和能量转换感兴趣？ 诗人：我在威斯康星大学举办的关于电化学发光（ECL）的研讨会之后提出了一个问题，我对此首先感兴趣。它发生在1960年代中期，发问者是杰出的物理化学家Farrington Daniels，他对太阳能转换很感兴趣。ECL涉及通过电化学方式产生自由基离子中间体来产生光，丹尼尔斯说，类似的东西很容易用电产生光，但是要用光产生电（或化学物质）则更加困难。我想我已经同意了，但是我没有看到如何向后运行ECL。但是，我开始考虑这一点，并得出结论，均匀光化学不可能是转化太阳能的有效途径，因为重组太快了，我认为更早甚至当前的工作都支持这一点。直到我阅读了本田-富士岛的论文（DOI：10.1038 / 238037a0）时，我才开始考虑将半导体用于此目的。我原本计划于1973年在巴黎放假，所以我不能马上开始。但是，我还是在这里做了一部分工作，以了解该领域，尤其是Heinz Gerischer撰写的有关半导体电极电化学的出色论文。EL ：您在1970年代和1980年代进行能源研究时遇到了哪些主要挑战？您是如何克服这些挑战的？ 巴德：我很幸运有一个优秀的研究生，肯·哈迪（Ken Hardee），他对这个问题很感兴趣，我们开始着手研究。第一个挑战是几乎所有的工作都是用TiO _2完成的单晶（金红石）。单晶很适合基础研究，因为它们倾向于相对纯净，并且更易于进行理论处理。但是，它们很昂贵，无法用于我们可能想尝试的许多材料。因此，我们一开始就决定尝试可以合成然后用于制造薄膜的多晶材料。实际上，我们的第一篇论文发表于1975年（DOI：10.1149 / 1.2134312）是对TiO ₂的描述。通过化学气相沉积（CVD）沉积的。这出奇地好，我们可以以此复制本田-藤岛的实验。金红石的一个公认的问题是其大的带隙3 eV，这意味着它仅吸收约4％的太阳光谱。因此，我们开始寻找带隙较小的氧化物。肯（Ken）是第一个在赤铁矿上制作和试用PEC的人（1976，DOI：10.1149 / 1.2132984）。另一个挑战是将半导体的性能，特别是带能和表面态能量的中间能级与电化学性能相关联。水中可用的热力学电化学窗口太小，无法绘制出大多数感兴趣的太阳能转换半导体图。因此，在1975年的此类研究中，必须使用非水溶剂，例如乙腈（DOI：10）。1021 / ja00859a007）。我的优秀博士后史蒂夫·弗兰克（Steve Frank）进行了TiO的研究₂并在导带边缘以下找到约0.7 eV的电平。非质子传递溶剂的另一个优点是可以使用多种氧化还原对。这种溶剂在以后的研究中被相当频繁地使用，例如以提高半导体在辐射下的稳定性。理解控制半导体/液体界面稳定性的因素是另一个挑战。我当时是作为Fairchild学者在加州理工学院度过休假的，而马克·赖顿（Mark Wrighton）也曾独立访问麻省理工学院，在此领域取得了重要进展。1977年的一个早晨，马克（Mark）于1977年到我的办公室讨论这个问题，然后我们想到了一个相当简单的热力学证明稳定性（DOI：10.1149 / 1.2133140）。亨氏格里舍尔EL：您是在紫外线照射的TiO ₂粒子系统中建立自由基形成和化学转变的先驱。您在半导体表面研究的化学反应成为光催化的基础。是什么导致您如此早地确定光催化领域的优势？诗人：我们开始考虑扩大光电化学电池进行化学反应的可能性。实际上，似乎材料成本（例如电极和隔板）以及已知的电化学电池高昂的投资成本将使实际利用变得非常困难，特别是在当前半导体所获得的低效率的情况下。我们发现，半导体粉末有可能进行类似的光化学反应并简化规模化生产，例如在太阳池中。我们了解使用小颗粒可能遇到的困难，例如缺乏有效分离载流子的合适界面区域，但我们认为值得尝试。我们使用了P-25 TiO ₂，它相对便宜，并且由锐钛矿和金红石颗粒组成，微米级聚集在nm范围内。史蒂夫·弗兰克（Steve Frank）在1977年研究了氰化物水溶液在人工和日光照射下的行为，并证明了氰化物的有效去除（DOI：10.1021 / ja00443a081）。这些实验非常容易，因此当Bernhardt Kraeutler成为博士后时，我们决定尝试在1977年扩展这些实验。例如，可以使用相同的策略来分解乙酸盐并形成乙烷，我们称之为光-科尔比反应（在类似的电化学反应之后）（DOI：10.1021 / ja00465a065），并在1978年提出了一条新的乙酸与甲烷形成甲烷的途径（DOI：10.1021 / ja00475a049）。我们还发现，通过赋予颗粒表面微分反应性，我们可以使这些颗粒反应更有效。1978年，我们可以通过在TiO上沉积铂来实现_̀2并可以用乙酸氧化产生的电子进行光化学处理（DOI：10.1021 / ja00481a059）。该镀铂的粉末后来用于许多其他反应，并且也可以使用不同半导体的粉末（如CdS和WO _3），还可以沉积其他金属（如Cu）。实际上，各种粉末在非均相光催化中的应用范围很广。例如，Kraeutler和Harold Reiche在1979年证明可以进行自由基聚合。范富仁（Frank）Fan展示了TiO _2的光敏性酞菁在对苯二酚的氧化中的作用（DOI：10.1021 / ja00514a056）。1980年对原理和其中大部分工作进行了回顾。（1）1981年，温德尔·邓恩（Wendell Dunn）的一名学生表明，带有惰性电极触点的搅拌粉末悬浮液“浆状电极”可以用作PEC电极（DOI ：10.1149 / 1.2127378）。在我们的多相光催化实验中，最有趣的也许是提供了APEC等效的著名的Urey-Miller火花实验的实验，其中Dunn和Aikawa证明了镀铂的TiO ₂在水，甲烷和氨的混合物照射下产生氨基酸（DOI：10.1021 / ja00413a020）。均相光催化的几个概念已申请专利，这些概念已获得许可，可以进行更大规模的研究，例如从水中去除有毒化学物质。这些对我来说很有趣，因为它们展示了大规模PEC操作的可能性和问题。例如，明显的地面太阳辐射间歇性问题意味着仅约三分之一的时间使用了固定设备。因此，在需要连续处理废水的水净化实验中，最好使用人造灯并全天候工作。抽水成本显然也是不可忽略的因素。到底，EL ：光催化的当前焦点是在水分解和CO ₂还原领域。设计经济上可持续的实用设备还有很长的路要走。您是否介意光催化作为储能产品组合的一部分的潜力？诗人：这是一个难题，因为它在很大程度上取决于经济因素和可用的替代能源技术。让我回到1990年代初期，并在当时正在开展的工作中进行讨论。此时，PEC概念已经相当成熟，电化学，光化学和半导体物理的融合使人们对过程和可能性有了更好的了解。例如，在德克萨斯大学（University of Texas）成立了一个由教师，学生和博士后组成的财团，以解决由天然气研究所（GRI）资助的实际水分解的可能性。该小组的成员包括Marye Anne Fox，Tom Mallouk和Prashant Kamat。出现了许多有用的概念，例如“集成化学系统”的概念，其中涉及半导体，催化剂等的更复杂的系统。需要获得期望的结果。这项合作的结果是，在化学研究报告专门介绍了化学中的许多“圣杯”，例如太阳能产生氢。这个论述讨论了产生成功的PEC系统的因素。（2）我认为，即使经过20多年，本文中的许多想法仍然有意义。人类一直以生物质的形式依赖太阳能，并在以后的大部分时间内储存化石燃料。除非我们发现可以利用的新能源，否则各种配置的太阳能仍可能是未来的能源。EL：许多年轻的研究人员渴望从事能源研究。您能否为这些年轻的科学家提供一些成功秘诀？ 诗人：我可以尝试，但只有一些警告。首先，这取决于我们如何定义“成功”。我将其定义为表现良好的科学，即回答了一个重要而有趣的问题，或者组装并测试了一种有用的设备，最好是一种比现有技术更好的设备。其次，要理解，该建议来自与当今的科学文化截然不同的人。我的意思是说，科学家试图尽可能完整地讲述该研究的故事，引起人们对解释中所有仍未解决的问题的注意，并且对统计有效性和可重复性问题持诚实的态度。（3）恐怕当前的风格更像是二手车推销员的风格。最后，我认为我的建议并非专门针对能源研究。一般来说，我认为不应选择基于社会影响的研究，特别是在像“能源”这样庞大而复杂的领域。在这里确实无法产生社会影响。我也要避免使用“一周的潮流”，例如石墨烯，纳米粒子等。人们应该选择一个人，就像选择一个伴侣一样，即真的很喜欢这项研究，而不是做其他任何事情，来选择问题！此外，必须认识到，一个好的问题可能会遇到许多困难和“不起作用”的实验。但是，偶尔会得到一个漂亮的结果或发现，这一切都值得。可在ACS出版物网站上免费获得支持信息，网址为DOI：10.1021 / acsenergylett.7b00566。特别是在像“能源”一样庞大而复杂的领域。在这里确实无法产生社会影响。我也要避免使用“每周的潮流”，例如石墨烯，纳米粒子等。人们应该选择一个人，就像选择一个伴侣一样，即是真的很喜欢这项研究，而不是其他任何事情，而选择了这个问题！此外，必须认识到，一个好的问题可能会遇到许多困难和“不起作用”的实验。但是，偶尔会得到一个漂亮的结果或发现，这一切都值得。可在ACS出版物网站上免费获得支持信息，网址为DOI：10.1021 / acsenergylett.7b00566。特别是在像“能源”一样庞大而复杂的领域。在这里确实无法产生社会影响。我也要避免使用“每周的潮流”，例如石墨烯，纳米粒子等。人们应该选择一个人，就像选择一个伴侣一样，即是真的很喜欢这项研究，而不是其他任何事情，而选择了这个问题！此外，必须认识到，一个好的问题可能会遇到许多困难和“不起作用”的实验。但是，偶尔会得到一个漂亮的结果或发现，这一切都值得。可在ACS出版物网站上免费获得支持信息，网址为DOI：10.1021 / acsenergylett.7b00566。一个人应该选择一个人，就像选择一个伴侣一样选择问题，也就是说，他真的很喜欢这项研究，而不是几乎所有其他事情都做到了！此外，必须认识到，一个好的问题可能会遇到许多困难和“不起作用”的实验。但是，偶尔会得到一个漂亮的结果或发现，这一切都值得。可在ACS出版物网站上免费获得支持信息，网址为DOI：10.1021 / acsenergylett.7b00566。一个人应该选择一个人，就像选择一个伴侣一样选择问题，也就是说，他真的很喜欢这项研究，而不是几乎所有其他事情都做到了！此外，必须认识到，一个好的问题可能会遇到许多困难和“不起作用”的实验。但是，偶尔会得到一个漂亮的结果或发现，这一切都值得。可在ACS出版物网站上免费获得支持信息，网址为DOI：10.1021 / acsenergylett.7b00566。

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A Conversation with Al Bard

Allen J. Bard was born in New York City on December 18, 1933 and grew up and attended public schools there, including the Bronx High School of Science (1948–1951). He attended The City College of the College of the City of New York (CCNY) (B.S., 1955) and Harvard University (M.A., 1956, Ph.D., 1958). Dr. Bard joined the faculty at The University of Texas at Austin (UT) in 1958 and has spent his entire career there. He has been the Hackerman-Welch Regents Chair in Chemistry at UT since 1985. He spent a sabbatical in the CNRS lab of Jean-Michel Savéant in Paris in 1973 and a semester in 1977 at the California Institute of Technology, where he was a Sherman Mills Fairchild Scholar. He was also a Baker lecturer at Cornell University in the spring of 1987 and the Robert Burns Woodward visiting professor at Harvard University in 1988. He has worked as mentor and collaborator with 99 Ph.D. students, 18 M.S. students, over 200 postdoctoral associates, and numerous visiting scientists. He has published 988 peer-reviewed research papers, 75 book chapters, and other publications, and he has received over 23 patents. He has authored three books: Chemical Equilibrium (1966), Electrochemical Methods—Fundamentals and Applications (1980, 2nd Ed., 2001, with L. R. Faulkner), and Integrated Chemical Systems: A Chemical Approach to Nanotechnology (1994). He served as Editor-in-Chief of the Journal of the American Chemical Society 1982–2001. His many awards include the ACS Priestley Medal (2002), the Welch Foundation Award in Chemistry (2004), the Wolf Foundation Prize (2008), the 2011 National Medal of Science (2011), and The Enrico Fermi Award (2013). His research interests involve the application of electrochemical methods to the study of chemical problems and include investigations in scanning electrochemical microscopy, electrogenerated chemiluminescence, and photoelectrochemistry. Father of Modern Electrochemistry is a term often applied to Allen (Al) J. Bard, Professor of Chemistry, University of Texas at Austin. For nearly five decades he has remained a great visionary in identifying key areas in energy research (Figure 1). From fundamental electrochemistry to electrochemiluminescence, from photoinduced processes at electrodes to dye sensitization, from semiconductor particle photocatalysis to single-crystal semiconductor photoelectrochemistry, he has made seminal contributions since the 1970s. He has nurtured photoelectrochemistry for nearly five decades and trained several generations of students and postdoctoral researchers who have become successful energy researchers. His lifelong research contributions have been recognized through the Priestley Medal, the American Chemical Society’s highest honor. In 2011 he was also awarded the National Medal of Science by President Barak Obama. Figure 1. With Prof. Allen J. Bard during a recent visit to University of Texas at Austin. (Photo courtesy of P. Kamat). As the first oil crisis appeared in the 1970s, Prof. Al Bard took the initiative to engage in renewable energy research and publish a series of papers related to semiconductor photoelectrochemistry and photocatalysis. These early papers provided fundamental principles of photoelectrochemical/photocatalytic conversion of light energy into electrical energy or chemical energy. Be it a design of a new solar cell or an energy storage device of water-splitting and CO₂ reduction, we find his published work highly informative when carrying out modern-day energy research (Figure 2). The following conversation provides some insights into the visionary world of Prof. Allen Bard. Figure 2. Pivotal contributions of Prof. Bard in the area of semiconductor photoelectrochemistry and photocatalysis provide the basis for modern-day energy research. EL (ACS Energy Letters): How did you become interested in photoelectrochemistry and energy conversion during the early years of your career? Bard: I first became interested in this as a result of a question after a seminar on electrogenerated chemiluminescence (ECL) I was giving at the University of Wisconsin. It took place in the middle 1960s, and the questioner was the distinguished physical chemist Farrington Daniels, who had long been interested in solar energy conversion. ECL involves the production of light through the electrochemical generation of radical ion intermediates, and Daniels said something like it is easy to produce light from electricity, but much more difficult to produce electricity (or chemicals) from light. I think I answered that I agreed, but I did not see how one could run ECL backward. However, I started to think about this and concluded that homogeneous photochemistry was unlikely to be an efficient route for the conversion of solar energy, because recombination would be too fast, and I think earlier and even current work supports this. It was only when I read the Honda–Fujishima paper (DOI: 10.1038/238037a0) that I started to think about the use of semiconductors for this purpose. I was scheduled to go on a sabbatical in Paris in 1973, so I could not get started on it right away. I did partly, however, use my time there to learn about the field, especially the excellent papers on electrochemistry at semiconductor electrodes by Heinz Gerischer. EL: What were some of the major challenges that you encountered in carrying out energy research in the 1970s and 1980s? How did you overcome these challenges? Bard: I was fortunate to have an excellent graduate student, Ken Hardee, who was interested in this problem, and we started to work on it. A first challenge was that almost all work had been done with TiO₂ single crystal (rutile). Single crystals were good for fundamental studies because they tended to be relatively pure and more amenable to theoretical treatment; however, they were expensive and not available for many materials that we might want to try. So early on we decided to try polycrystalline materials that we could synthesize and then use to fabricate thin films. In fact, our first paper published in 1975 (DOI: 10.1149/1.2134312) was a description of TiO₂ that was deposited by chemical vapor deposition (CVD). This worked surprisingly well, and we could replicate the Honda–Fujishima experiments with this. A well-recognized problem with rutile was its large band gap, 3 eV, which meant it absorbed only about 4% of the solar spectrum. Thus, we began looking for oxides with smaller band gaps; Ken was the first one to make and try out the PEC on hematite (1976, DOI: 10.1149/1.2132984). Another challenge was relating the properties of semiconductors, especially the band energies and intermediate levels of surface state energies, to the electrochemical properties. The thermodynamic electrochemical window available in water is too small to map most semiconductors of interest in solar energy conversion; so, one must use nonaqueous solvents, e.g. acetonitrile, for such studies in 1975 (DOI: 10.1021/ja00859a007). An excellent postdoc of mine, Steve Frank, undertook the study of TiO₂ and found a level about 0.7 eV below the conduction band edge. An additional advantage of the aprotic solvent was the availability of a wide range of redox couples that could be employed. Such solvents were used fairly frequently in later studies, for example to improve the stability of the semiconductor under the radiation. Understanding the factors that control the stability of the semiconductor/liquid interface was another challenge. I was spending a sabbatical at Caltech as a Fairchild scholar at the same time that Mark Wrighton, who had independently been making important advances in this field at MIT, was also visiting. One morning, Mark came to my office in 1977 to discuss this problem, and we came up with a fairly simple thermodynamic justification of the stability (DOI: 10.1149/1.2133140). Heinz Gerischer, a leader in research in this field for many years, came up with a similar proposal at about the same time. EL: You were the pioneer in establishing the radical formation and chemical transformations in UV-irradiated TiO₂ particle systems. The chemical reactions you studied at semiconductor surfaces became the basis of photocatalysis. What led you to identify the strength of the photocatalysis field so early? Bard: We began to think about the possibility of scaling up the photoelectrochemical cells to do chemistry. It really seemed that the cost of materials, e.g. electrodes and separators, as well as the known high capital costs of electrochemical cells, would make practical utilization pretty difficult, especially at the low efficiencies that were being obtained with the current semiconductors. It occurred to us that it might be possible for powders of semiconductors to carry out similar photochemical reactions and simplify scale-up, for example in solar ponds. We understood the possible difficulties with using small particles, such as the lack of suitable interfacial fields for efficient separation of carriers, but we thought it was worth a try. We used P-25 TiO₂, which is relatively inexpensive and which consists of anatase and rutile particles in the range of nm in μm aggregates. Steve Frank in 1977 looked at the behavior of aqueous cyanide solutions under artificial and solar irradiation and demonstrated quite efficient removal of cyanide (DOI: 10.1021/ja00443a081). These experiments were quite easy, and so when Bernhardt Kraeutler came as a postdoc we decided to try to extend these experiments in 1977. For example, one could use the same strategy to decompose acetate and form ethane and what we called the photo-Kolbe reaction (after a similar electrochemical reaction) (DOI: 10.1021/ja00465a065), and in 1978 a new pathway with acetic acid to form methane (DOI: 10.1021/ja00475a049). It also occurred to us that we could make these particle reactions more efficient by giving the surface of the particle differential reactivity. In 1978 we could do this by depositing platinum on the TiO_̀2 and could carry this out photochemically with the electrons that resulted from acetic acid oxidation (DOI: 10.1021/ja00481a059). This platinized powder was later used for many other reactions, and powders of different semiconductors, like CdS and WO₃, also worked, and other metals, like Cu, could also be deposited. The scope of application of various powders in heterogeneous photocatalysis was wide indeed. For example, Kraeutler and Harold Reiche in 1979 showed that radical polymerization could be carried out. Fu-Ren (Frank) Fan demonstrated photosensitization of TiO₂ by phthalocyanine in the oxidation of hydroquinone (DOI: 10.1021/ja00514a056). A review of the principles and much of this work appeared in 1980.(1) A student, Wendell Dunn, in 1981 showed that the stirred powder suspensions, “slurry electrodes”, with an inert electrode contact, could serve as PEC electrodes (DOI: 10.1149/1.2127378). Perhaps the most interesting of our heterogeneous photocatalysis experiments was one that provided APEC equivalent of the famous Urey–Miller spark experiment, where Dunn and Aikawa showed that platinized TiO₂ produces amino acids under irradiation of a mixture of water, methane, and ammonia (DOI: 10.1021/ja00413a020). Several of the concepts of homogeneous photocatalysis were patented, and these were licensed to allow larger scale studies, for example in removing toxic chemicals from water; these were interesting to me because they demonstrated the possibilities and problems of larger-scale PEC operations. For example, the obvious problem of the intermittency of terrestrial solar irradiation meant that capital equipment was used only about one-third of the time. Thus, in the water purification experiments, where it was desirable to continuously treat a waste stream, it was better to employ artificial lamps and operate around the clock. The cost of pumping was also clearly a non-negligible factor. In the end, the demonstration project was a success in terms of decomposing toxic waste but did not compete economically with alternative processes, e.g. simple adsorption on activated carbon. EL: The current focus of photocatalysis is in the area of water splitting and CO₂ reduction. We still have a long way to go to design economically sustainable, practical devices. Would you mind commenting on the potential of photocatalysis as part of the energy storage portfolio? Bard: This is a difficult question, because it depends importantly on economic factors and available alternative energy technologies. Let me go back to the early 1990s and discuss this in the context of work being done then. At this time, PEC concepts had matured considerably, and the melding of electrochemistry, photochemistry, and semiconductor physics resulted in a better understanding of the processes and possibilities; for example, at the University of Texas a consortium of faculty, students, and postdocs formed to address the possibility of practical water splitting, funded by the Gas Research Institute (GRI). Among the members of this group were Marye Anne Fox, Tom Mallouk, and Prashant Kamat. Many useful concepts emerged, e.g. that of “integrated chemical systems”, in which a more complex system involving semiconductor, catalyst, etc. was needed to obtain desired results. One result of this collaboration was the publication of an account in a special issue of Accounts of Chemical Research devoted to a number of “Holy Grails” in chemistry, like solar energy to produce hydrogen. This account discussed factors in producing a successful PEC system.(2) I think many of the ideas in this paper, even after more than 20 years, are still relevant. Humans have relied on solar energy in the form of biomass and later stored fossil fuels for most of their existence. Unless we discover new forms of energy that can be tapped, solar energy in a variety of configurations is still probably the energy of the future. EL: Many young researchers aspire to engage in energy research. Could you please provide some tips to these young scientists on how to be successful? Bard: I can try, but only with a few caveats. For one, it depends how we define “successful”. I would define it as having performed good science, i.e. answered an important and interesting question or having assembled and tested a useful device, preferably one that is better than the existing state-of-the-art. Second, with an understanding that this advice comes from someone who grew up in a very different science culture than that which currently exists. By this I mean that a scientist tries to tell as complete a story about the research as possible, calling attention to any still unsolved problems in the interpretation, and is honest in questions of statistical validity and reproducibility.(3) I’m afraid the current style is more like that of a used-car salesman. Finally, I do not think my advice is specific for energy research. In general, I do not think one should choose research based on societal impact, especially in a field as large and complex as “energy”. Really having a societal impact here is quite improbable. I would also avoid the “fad of the week”, e.g., graphene, nanoparticles, etc. One should select the problem the same way one selects a mate, i.e. really love the research and rather be doing that than almost anything else! Moreover, one must recognize that a good problem may be plagued with lots of difficulties and experiments that “do not work”. However, one gets a beautiful result or discovery once in a while, and that makes it all worth it. The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsenergylett.7b00566.

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Complete citation information for articles cited in the text (PDF) Views expressed in this Energy Focus are those of the author and not necessarily the views of the ACS. The author declares no competing financial interest. This article references 3 other publications.

更新日期：2017-07-13

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