Co-modification of WO3 nanoplates with β-FeOOH/carbon quantum dots combined with plasma treatment enables high-efficiency photoelectrochemical characteristics

Abstract

Dual-modification strategies of conventional WO₃ photoanodes are implemented to rationally modulate their photocatalytic activity under irradiation of stimulated sunlight. These are first accomplished by the uniform incorporation of β-FeOOH nanoclusters with WO₃ hosts as shell/core heterostructures, followed by argon plasma treatment, which provides synergistic effects for the beneficial transmission and injection of photogenerated holes, including the dramatic increase in oxygen-vacancy mediated active sites due to the in situ formation of Fe²⁺/Fe³⁺-coexisting FeOOH facets combined with oxygen-deficient WO₃ lattices, and great upward band bending at hybrid photoanode/electrolyte interfaces. Moreover, inspired by naturally existing features, such as nut/scale endowed pine-cone structures, anchoring carbon quantum dots (CQDs) on plasma-treated FeOOH/WO₃ photoanodes is artificially imitated to access the band engineering of photoanode design. These multilevel structures offer an effective hole channel that facilitates the extraction of photoexcited holes and direct photovoltaic effect on CQDs, displaying a faradaic efficiency of 88.0% for oxygen generation. In addition, remarkable surface efficiency (83.3%), a substantial decrease in the open-circuit voltage (0.425 V) and interfacial charge transfer resistance (215 Ω) over those of pristine WO₃ photoanodes (38.2%, 0.425 V and 2250 Ω) are observed.