Carbon-Driven Interfacial Charge Redistribution in TiO₂-Ni(OH)₂ Photoanodes for Formate Production From Plastics and...

Coupling photoelectrochemical (PEC) waste plastic reforming with CO₂ utilization to co-produce value-added chemicals offers a promising strategy to mitigate plastic pollution and carbon emissions. Yet, achieving high selectivity still requires highly active plastic-reforming photoanodes and effective integration with CO₂ reduction photocathodes. Here, an ultrathin carbon interlayer was introduced into Ni(OH)₂-TiO₂ (named Ni(OH)₂/C/TiO₂) photoanode to modulate its interfacial electronic structure, thereby converting alkaline-pretreated polyethylene terephthalate (PET) into formate. The optimized photoanode delivered a formate yield 2.7 times that of bare Ni(OH)₂/TiO₂ with a stable Faradaic efficiency (FE) of 96.2% across 0.4-1.2 V versus RHE. The enhancement mechanism of the carbon layer was elucidated by in situ characterization and theoretical calculations. The carbon layer modulated interfacial charge distribution at the photoanode, which not only facilitates charge transfer but also strengthens adsorption of PET-derived ethylene glycol and stabilizes key intermediates, achieving high selectivity for formate. Additionally, a stable PEC tandem cell was assembled that co-converted PET and CO₂ to formate without external bias, attaining a formate FE of 171.1% (FE_max = 192.2% at 0.3 V). This study provides insights into the role of carbon layers in optimizing interfacial reactions, guiding the development of an integrated PEC cell for simultaneous valorization of plastics and CO₂.