Search for: All records

CuFeO2 delafossite materials have been researched for their promising photoactivity for CO2 reduction (CO2R) due to their intrinsic p-type conductivity. However, its practical application is limited by its poor stability and low photocurrent densities. In this work, we investigated the mechanistic origin of CuFeO2 degradation under CO2R conditions. Through photoelectrochemical measurements combined with ex situ X-ray photoelectron spectroscopy and in situ surface-enhanced Raman spectroscopy, we show that CO2-saturated sodium bicarbonate electrolytes enhance photoelectrochemical corrosion by facilitating iron leaching from the catalyst. Systematic control experiments reveal that this instability is not governed solely by thermodynamic surface stability but arises from a nonequilibrium interfacial speciation of CO2, bicarbonate, and carbonate. The presence of carbonate species at the catalyst interface facilitates iron(II) complexation and degrades the CuFeO2 surface. These findings establish carbonate-driven photoelectrochemical corrosion as a key degradation pathway for CuFeO2 and underscore the importance of speciation at the interface-electrolyte in dictating the long-term performance of a catalyst for CO2R.   

Conjugated polymer nanoparticles (CPNs or Pdots) have become increasingly popular fluorophores for multimodal applications that combine imaging with phototherapeutic effects. Reports of CPNs in photodynamic therapy applications typically focus on their ability to generate singlet oxygen. Alternatively, CPN excited states can interact with oxygen to form superoxide radical anion and a CPN-based hole polaron, both of which can have deleterious effects on fluorescence properties. Here, we demonstrate that CPNs prepared from the common conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole)] (PFBT, also known as F8BT) generate superoxide upon irradiation. We use the same CPNs to detect superoxide by doping them with a superoxide-responsive hydrocyanine dye developed by Murthy and co-workers. Superoxide induces off-to-on fluorescence switching by converting quenching hydrocyanine dyes to fluorescent cyanine dyes that act as fluorescence resonance energy transfer (FRET) acceptors for PFBT chromophores. Amplified FRET from the multichromophoric CPNs yields fluorescence signal intensities that are nearly 50 times greater than when the dye is excited directly or over 100 times greater when signal readout is from the CPN channel. The dye loading level governs the maximum amount of superoxide that induces a change in fluorescence properties and also influences the rate of superoxide generation by furnishing competitive excited state deactivation pathways. These results suggest that CPNs can be used to deliver superoxide in applications in which it is desirable and provide a caution for fluorescence-based CPN applications in which superoxide can damage fluorophores.