Hydrogenated TiO₂ Nanorod Arrays Decorated with Carbon Quantum Dots toward Efficient Photoelectrochemical Water Splitting

Abstract

Limited light harvesting and charge collection are recognized as grand challenges for the exploration of highly efficient TiO2 photoanodes. To overcome these intrinsic shortcomings, we reported the designed photoanode based on TiO2 nanoarrays with both hydrogenation treatment and surface decoration of carbon quantum dots (CQDs) toward efficient photoelectrochemical water splitting. The results revealed that hydrogenation treatment could cause the formation of oxygen vacancies to suppress the recombination of photoinduced carriers. Meanwhile, the decorated CQDs could not only play as the electron reservoirs to trap photoinduced electrons but also remarkably enhance the solar light harvesting due to their upconversion effect. The as-fabricated photoanodes exhibited a large photocurrent density of ∼3.0 mA/cm2 at 1.23 V versus reversible hydrogen electrode under simulated sunlight, which was the highest one among hydrogenated TiO2 photoanodes ever reported and was ∼6 times that of pristine analogues.

The role of carbon dots – derived underlayer in hematite photoanodes

“…31 Moradlou et al 23 reported the use of carbon quantum dots as nano-scaffolds for α-Fe 2 O 3 growth, which led to a remarkable photoelectrochemical performance, due to the improvement in charge-transfer rate and suppression of electron-hole recombination derived from the increased hole-diffusion length in conducting nano-scaffold structure. Liang and coworkers 32 found that surface decoration of carbon quantum dots on TiO 2 photoanodes could reduce the electron-hole recombination, attributed to the electron-trapping property of carbon quantum dots. Very recently, a N-doped carbon overlayer applied on α-Fe 2 O 3 photoanodes was shown to suppress interface charge recombination by passivating surface states, thus improving the photocurrent of hematite photoanodes.…”

Deposition of a ZnO Nanolayer on TiO2 Nanorods Nanoarrays with Tailored Thickness towards Boosted Photoelectrochemical Hydrogen Production Activity

“…It is worthy to note that the diameter of arc on Nyquist plots is closely related with electron‐transfer resistance value . Typically, a smaller semicircle arc represents a smaller electron‐transfer resistance value, thereby represents a faster interfacial charge migration . It can be clearly observed that the TiO 2 @ZnO 30nm electrode possesses the smallest semicircle arc as compared to the other sample photoanodes, confirming the lowest interfacial charge transfer resistance.…”

“…It is found that all the EIS curves of the sample photoanodes display obvious semicircle arc in high‐to‐medium frequency range, resulted from the charges transfer process. It is worthy to note that the diameter of arc on Nyquist plots is closely related with electron‐transfer resistance value . Typically, a smaller semicircle arc represents a smaller electron‐transfer resistance value, thereby represents a faster interfacial charge migration .…”

Ni/Si-Codoped TiO2 Nanostructure Photoanode for Enhanced Photoelectrochemical Water Splitting

“…They reported that the loading of Au nanoparticles onto the nanotube arrays remarkably increased the photocurrent density up to 1.67 times. Liang et al [64] decorated hydrogenation-treated TiO 2 with carbon quantum dots (CQDs). The highest photocurrent density of the composite was six times higher than that of pristine TiO 2 .…”