Understanding Structure-Activity Relationship in Pt-loaded g-C 3 N 4 for Efficient Solar- Photoreforming of Polyethylene Terephthalate Plastic and Hydrogen Production.

Coupling the hydrogen evolution reaction with plastic waste photoreforming provides a synergistic path for simultaneous production of green hydrogen and recycling of post-consumer products, two major enablers for establishment of a circular economy. Graphitic carbon nitride (g-C 3 N 4 ) is a promising photocatalyst due to its suitable optoelectronic and physicochemical properties, and inexpensive fabrication. Herein, a mechanistic investigation of the structure-activity relationship of g-C 3 N 4 for poly(ethylene terephthalate) (PET) photoreforming is reported by carefully controlling its fabrication from a subset of earth-abundant precursors, such as dicyandiamide, melamine, urea, and thiourea. These findings reveal that melamine-derived g-C 3 N 4 with 3 wt.% Pt has significantly higher performance than alternative derivations, achieving a maximum hydrogen evolution rate of 7.33 mmol H2  g cat -1  h -1 , and simultaneously photoconverting PET into valuable organic products including formate, glyoxal, and acetate, with excellent stability for over 30 h of continuous production. This is attributed to the higher crystallinity and associated chemical resistance of melamine-derived g-C 3 N 4 , playing a major role in stabilization of its morphology and surface properties. These new insights on the role of precursors and structural properties in dictating the photoactivity of g-C 3 N 4 set the foundation for the further development of photocatalytic processes for combined green hydrogen production and plastic waste reforming.