Proton transport enabled by a field-induced metallic state in a semiconductor heterostructure
Authors: C Chen
J F Li
H B Song
L Liu
J S Kim
Y Wu
J Wei
B Zhu
M Akbar
L R Zheng
M Huang
Q Shi
Journal: Science (2020)
Discipline: Multidisciplinary
Keywords: Semiconductor tuning; Proton conductor; Proton ceramic fuel cells; Electrolyte conductivity; Na x CoO2/CeO2 heterostructure
Affiliations: Engineering Research Center of Nano-Geo Materials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, China., Engineering Research Center of Nano-Geo Materials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, China.  ., Energy Storage Joint Research Center, Southeast University School of Energy and Environment, Southeast University, Nanjing, 210096, China., Key Laboratory of Ferro and Piezoelectric Materials and Devices of Hubei Province, Faculty of Physics and Electronic Sciences, Hubei University, Wuhan, 430062, China., Huazhong University of Science and Technology, Wuhan, 430074, China., College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China., Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China., Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough LE11 3TU, UK.

Abstract:  Tuning a semiconductor to function as a fast proton conductor is an emerging strategy in the rapidly developing field of proton ceramic fuel cells (PCFCs). The key challenge for PCFC researchers is to formulate the proton-conducting electrolyte with conductivity above 0.1 siemens per centimeter at low temperatures (300 to 600°C). Here we present a methodology to design an enhanced proton conductor by means of a Na x CoO2/CeO2 semiconductor heterostructure, in which a field-induced metallic state at the interface accelerates proton transport. We developed a PCFC with an ionic conductivity of 0.30 siemens per centimeter and a power output of 1 watt per square centimeter at 520°C. Through our semiconductor heterostructure approach, our results provide insight into the proton transport mechanism, which may also improve ionic transport in other energy applications. 

Retracted: No

PubPeer comments:
 Several of the figures in the supplementary materials section of this Science paper are directly reproduced from previously published works by the same group, although they purport to be from completely different fuel cell systems. Figure S9(b) from the Science article looks to be direct duplication of Figure 8(b) from a previous 2018 Int. J. Hyd. Energy paper (International Journal of Hydrogen Energy 43 (2018) 12739-17747 in Fig. 8 (b)) on a completely different type of fuel cell. The axes scales in the two figures are slightly different, but I extracted the plots from both papers and set the white background color to transparent so I could overlay them. When I lined up the x-axis and right y-axis (power density scales) from the two figures, the I-P data perfectly overlays. Similarly, if I line up the left right axis (voltage) scale, the I-V data perfectly overlay. I attach a powerpoint file with the comparisons. You can move the top (transparent) graphic which is the IJHE figure relative to the bottom graphic which is the Science plot to see what I mean. Similarly, in comparing Figure S10 in the Science paper with Figure 8(a) from another IJHE paper by the same group (published in 2017, International Journal of Hydrogen Energy 42 (2017) 17495-17503), they again appear to be identical, although the scale bar has been changed and the labels that the describe the type of fuel cell that the EM image purportedly represents have also been changed. , 
 Brought to my attention by a reader. Figure S10 of this paper (left) appears to look very similar to Figure 8b of a previous paper with some shared authors (right), i.e. Rong Xu et al. IJ Hydrog Energy (2017), doi: 10.1016 j.ijhydene.2017.05.218. Red boxes show the areas that look similar between the two figures. Yellow markings are part of the original figures. The two photos appear to be showing a different composite. Could the authors please clarify if these two images are supposed to show the same structure? Maybe I am misinterpreting the labels. ![file] , 
 The same reader also attended me to a possible similarity between Figure S9b of this paper (shown left) and Figure 8 of another paper with shared authors (shown right), i.e. Liang Liu et al. IJ Hydrogen Energy (2018), doi: 10.1016 j.ijhydene.2018.03.184. Figure S9b of this paper shows an additional line at 430 degrees not present in the 2018 figure but otherwise the graphs look similar. From the legends, the compounds tested in either paper appear to be different. Could the authors please clarify the similarities between these two figures? Were these showing the same measurements? ![file] , 
 At first sight, the three papers mentioned in #2 and #3, although sharing a common topic (new solid electrolytes for fuel cells), are unrelated: * Science (2020): the electrolyte is a $Na_{x}CoO_{2} CeO_{2}$ composite. * IJHE (2017): the electrolyte is a composite between a Cu Fe oxide and an yttrium stabilized zirconia. * IJHE (2018): the electrolyte is a $Sm_{2}O_{3} NiO$ composite. , 
 #2 Agree with your finding. I did an illustration by superimposing a semi-transparent inverted fig 8a from the 2017 paper over the fig S10 of the 2020 paper. It appears quite clear that they are almost a perfect match after scaling down the width of the fig 8a to 95%. Additionally, I looked at their scale bars. Taking the 100um bar as a true 100, then the 500um bar is only a bit shy of 250. Does it mean that at least one of the images was not used at its actual size? Appreciate if the authors can explain. ![] , 
 Figure S9(b) from the Science article looks to be direct duplication of Figure 8(b) from a previous 2018 Int. J. Hyd. Energy paper on a completely different type of sample. The axes scales in the two figures are slightly different, but I extracted the plots from both papers and set the white background color to transparent so I could overlay them. When I lined up the x-axis and right y-axis (power density scales) from the two figures, the I-P data perfectly overlays. Similarly, if I line up the left right axis (voltage) scale, the I-V data perfectly overlay. See the figure for comparision: ![file] ![file] , 
 Via: https: retractionwatch.com 2020 10 08 science-retracts-paper-as-authors-blame-pandemic-for-image-issues Retraction Y. Wu1, L. Liu1, Q. Shi1, C. Chen2, J. Wei3, J. F. Li3, L. R. Zheng4, H. B. Song1,* Science 09 Oct 2020: Vol. 370, Issue 6513, pp. 179 DOI: 10.1126 science.abe7205 The supplementary materials (SM) for our Report u201cProton transport enabled by a field-induced metallic state in a semiconductor heterostructureu201d (1) contained mistakes. Fig. S10 was incorrect. The image had been previously saved in an experimental database. The figure should have shown a schematic illustration. This mistake occurred when computer data was transferred from one student to another. Fig. S9B also raised questions. The image appears to be a copy of figure 8B in a 2018 paper in the International Journal of Hydrogen Energy (2). The tests producing the data for these two figures were performed during the same period of time. Because of the similarity between the IV-IP measurements of SN-120 and the NaxCoO2 CeO2 (x = 0.55) measurements, these data were wrongly saved in the same folder. Therefore, the final plotted fig. S9B in Science erroneously contains data from the figure in the 2018 paper. We repeated the experiment to replicate the data and found that the new outputs of two NaxCoO2 CeO2 (x 0.6) cells are above 550 mW cmu22122 at 520u00b0C, consistent with the data in fig. S9. These mistakes were related to recent location and personnel changes. Between June and September 2019, all laboratories of the Faculty of Materials Science and Chemistry, including ours, had to move to a new campus 30 km away. During the same time, author L. Liu graduated, but the ordinary data transfer to successors was temporarily discontinued. The manuscript was finalized between mid-December 2019 and March 2020, during the unprecedented lockdown of the city of Wuhan for coronavirus disease 2019. All authors who prepared the main manuscript and SM data were isolated in different cities and countries, without access to lab computers or database resources, which led to miscommunications. We take full responsibility for the accidental mistakes in the SM. We stand by our experimental design, theoretical calculations, main data, and analysis of low-temperature proton ceramic fuel cells. However, given the mistakes in the SM, we have decided to retract the Report. All authors except for B. Zhu, M. Huang, M. Akbar, and J. S. Kim approved this Retraction. ,