Catalysis sans catalyst loss: The origins of prolonged stability of graphene-metal-graphene sandwich architecture for oxygen reduction reactions

Abstract

AbstractOver the past several decades, the design of highly active and cost-effective catalysts and electrocatalyst has been the subject of intense research efforts.to 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 have been proposed in literature, such as catalyst particles detachment of the substrate, metal atom dissolution, agglomeration, Ostwald ripening, or corrosion of the carbon support, but with a lack of systematic studies, the causal relations between degradation and these proposed mechanisms remain ambiguous. Here, we report a systematic study of a catalyst system comprising of small particles and single atoms of Pt sandwiched between graphene layers, GR/Pt/GR where Pt-specific catalysis occurs through “chemically transparent” outer Gr layer(s). Experimental and computational analyses unravel the degradation mechanism of the studied electrocatalyst architecture for oxygen reduction reaction in acidic medium. 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 towards 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. The proposed Gr/metal/Gr architecture is not only applicable to other electrocatalytic reactions but can have several applications in sensors and biomedical fields.