Over the past decades, the design of active catalysts has been the subject of intense research efforts. However, there has been significantly less deliberate emphasis on rationally designing a catalyst system with a prolonged stability. A major obstacle comes from the ambiguity behind how catalyst degrades. Several degradation mechanisms are proposed in literature, but with a lack of systematic studies, the causal relations between degradation and those proposed mechanisms remain ambiguous. Here, a systematic study of a catalyst system comprising of small particles and single atoms of Pt sandwiched between graphene layers, GR/Pt/GR, is studied to unravel the degradation mechanism of the studied electrocatalyst for oxygen reduction reaction(ORR). Catalyst suffers from atomic dissolution under ORR harsh acidic and oxidizing operation voltages. Single atoms trapped in point defects within the top graphene layer on their way hopping through toward the surface of GR/Pt/GR architecture. Trapping mechanism renders individual Pt atoms as single atom catalyst sites catalyzing ORR for thousands of cycles before washed away in the electrolyte. The GR/Pt/GR catalysts also compare favorably to state‐of‐the‐art commercial Pt/C catalysts and demonstrates a rational design of a hybrid nanoarchitecture with a prolonged stability for thousands of operation cycles.
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Solvents are essential in synthesis, transfer, and device fabrication of 2D materials and their functionalized forms. Controllable tuning of the structure and properties of these materials using common solvents can pave new and exciting pathways to fabricate high‐performance devices. However, this is yet to be materialized as solvent effects on 2D materials are far from well understood. Using fluorine functionalized chemical vapor deposited graphene (FG) as an example, and in contrast to traditional “hard‐patterning” method of plasma etching, the authors demonstrate a solvent‐based “soft‐patterning” strategy to enable its selective defluorination for the fabrication of graphene‐FG lateral heterostructures with resolution down to 50 nm. In this strategy, the oxygen plasma etching process of patterning after graphene transfer is avoided and high quality surfaces are preserved through a physically continuous atomically thin sheet, which is critical for high performance photodetection, especially in the high‐speed domain. The fabricated lateral graphene heterostructures are further employed to demonstrate a high speed metal–semiconductor–metal photodetector (<10 ns response time), with a broadband response from deep‐UV (200 nm) to near‐infrared (1100 nm) range. Thanks to the high quality surface with much less defects due to the “soft‐patterning” strategy, the authors achieve a high deep‐UV region photoresponsivity as well as the ultrafast time response. The strategy offers a unique and scalable method to realize continuous 2D lateral heterostructures and underscores the significance of inspiring future designs for high speed optoelectronic devices.
