"Will Any Crap We Put into Graphene Increase Its Electrocatalytic Effect?" Prof. Martin Pumera of Brno University of Technology and co-workers recently published this paper in ACS Nano, an international scientific journal on nanoscience and nanotechnology. This work demonstrated the synthesis of graphene sheet doped with N, S, and P elements using a compound in bird poop, as well as its enhanced catalytic activities toward oxygen reduction reaction and hydrogen evolution reaction compared to graphene without the dopants.
This prospective article states that the current literature on electrocatalysis of graphene has been flooded with papers having little scientific insights or reasonable justifications. "It has become almost a paradigm that the once fantastic graphene for electrocatalysis is not so fantastic anymore and that we need to add something to it (i.e., a dopant) to make it great again," the authors opened the discussion with this sentence.
Afterward, the authors presented an experiment comparing the electrocatalytic activities of graphene with and without N, S, and P elements. The authors selected guano, a compound in bird poop, as the dopant precursor, due to its low cost, large abundance, and containing a plethora of elements (N, P, S, Cl, etc.). For the catalytic reactions, the authors studied oxygen reduction reaction (ORR) in fuel cells and hydrogen evolution reaction (HER) for hydrogen fuel generation, both of which are critical components for the sustainable energy landscape. Experimental results showed that the graphene sheets treated with guano exhibited consistently larger current densities than the untreated counterparts in both ORR (Fig. 1A) and HER (Fig. 1B), evidencing its improved electrocatalytic activities. In conclusion, the authors claimed that the "fever" of doped-graphene electrocatalysis should be cooled down, "Because doping graphene with cheap bird droppings produces more electrocatalytic materials than many complex multi-elemental doping procedures, we do not see any justification for such efforts, and we believe that researchers should focus their energy on other research directions."
Figure 1. Linear sweep voltammograms of different catalysts in (A) oxygen reduction reaction and (B) hydrogen evolution reaction. The higher current densities of Ho-GO-BD and Hu-GO-BD at -0.6 V mark their higher catalytic activities than the untreated counterparts. GC: glassy carbon; Ho(Hu)-GO: untreated graphene synthesized by the Hoffmann (Hummers) method; Ho(Hu)-GO-BD: guano-treated graphene synthesized by the Hoffmann (Hummers) method. Credit: ACS Nano.
The article received immediate attention after publication. The ACS Nano website shows that this article has been viewed for more than 40k views and tweeted worldwide since its publication on Jan. 14th, 2020. A Chinese WeChat news article highlighting this article achieved 100k reads within a day.
Besides popularity, this work has also aroused heated discussions globally among materials researchers. Some readers believed that this article timely revealed the problematic situation of the graphene-based catalysis field, and urged scientists to stay focused on innovative and meaningful projects, rather than producing massive mediocre and uninspiring papers. Other readers respectfully disagree with the authors. They thought that this work did not compare the catalytic properties of the guano-treated graphene with the benchmark, platinum/carbon, or other doped graphene sheets with much higher catalytic activities than the undoped graphene. They also criticized that the paper overlooked numerous previously published works that were comprehensively designed, thoroughly performed, and reasonably discussed, which offered valuable insights into the design and catalysis of doped graphene materials. This group of scientists argued that diverting researchers away from doping graphene for electro-catalysis was illogical.
Although it is not crystal clear about what should be the superior treatments for graphene-based catalysts, this article has motivated researchers to re-evaluate and reflect with the efforts in electrocatalysis. I appreciate the authors for bringing up the issue of doped graphene, as peer discussion is necessary to propel the healthy development of any research fields.
Tianyu Liu acknowledges Dr. Aashutosh Mistry of the U.S. Argonne National Laboratory for his valuable revision suggestions.
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