Abstract
Conjugated polymers are emerging as alternatives to inorganic semiconductors for the photoelectrochemical water splitting. Herein, semi-transparent poly(4-alkylthiazole) layers with different trialkylsilyloxymethyl (R3SiOCH2−) side chains (PTzTNB, R = n-butyl; PTzTHX, R = n-hexyl) are applied to functionalize NiO thin films to build hybrid photocathodes. The hybrid interface allows for the effective spatial separation of the photoexcited carriers. Specifically, the PTzTHX-deposited composite photocathode increases the photocurrent density 6- and 2-fold at 0 V versus the reversible hydrogen electrode in comparison to the pristine NiO and PTzTHX photocathodes, respectively. This is also reflected in the substantial anodic shift of onset potential under simulated Air Mass 1.5 Global illumination, owing to the prolonged lifetime, augmented density, and alleviated recombination of photogenerated electrons. Additionally, coupling the inorganic and organic components also enhances the photoabsorption and amends the stability of the photocathode-driven system. This work demonstrates the feasibility of poly(4-alkylthiazole)s as an effective alternative to known inorganic semiconductor materials. We highlight the interface alignment for polymer-based photoelectrodes.
Highlights
In view of the often predicted fossil fuel exhaustion and corresponding environment pollution, renewable energy sources have attracted widespread attention.[1−3] In the search for potential candidates, hydrogen produced from solar water splitting is a supposedly clean alternative, owing to its high mass energy density and ease of transportation.[4−7] Photoelectrochemical (PEC) water splitting driven by solar light is an intriguing route to directly convert solar energy into storable hydrogen energy, which is sustainable and potentially economically feasible.[8−10] PEC cells perform redox reactions actuated by charge carriers created by incident photons.[11,12]
The water reduction efficiency highly depends upon the intrinsic electronic band structure of the photocathode, because it is essentially correlated with the sunlight absorption, charge carrier separation, and photochemical stability.[13]
The electrochemical impedance spectroscopy (EIS) was documented at a direct current (DC) bias of 0.1 VRHE in the frequency range from 20 kHz to 0.2 Hz
Summary
In view of the often predicted fossil fuel exhaustion and corresponding environment pollution, renewable energy sources have attracted widespread attention.[1−3] In the search for potential candidates, hydrogen produced from solar water splitting is a supposedly clean alternative, owing to its high mass energy density and ease of transportation.[4−7] Photoelectrochemical (PEC) water splitting driven by solar light is an intriguing route to directly convert solar energy into storable hydrogen energy, which is sustainable and potentially economically feasible.[8−10] PEC cells perform redox reactions actuated by charge carriers (electrons and holes) created by incident photons.[11,12] In a photocathode-driven system, disassociated electrons reduce water and evolve hydrogen at the surface of the photocathode and the holes migrate to the counter electrode to oxidize water/hole scavengers, possibly with the assistance of a bias to accelerate the transportation.[13]. Conjugated polymers are promising to revise the behavior of conventional photoelectrodes as a result of the probability of tailoring the optical, electric, and morphological features at the molecular level.[3,24] Miyauchi et al coated with poly(3,4ethylenedioxythiophene) (PEDOT) a CdS and CdSe quantum-dot-sensitized TiO2 photoelectrode, which helped to prevent the photocorrosion and to mitigate the recombination, leading to an upgraded photocurrent of approximately 15 mA cm−2 in the absence of applied bias.[25] On the other hand, a recent work by Xu et al used polythiophene to passivate the surface states of the CuBi2O4 photocathode. The resultant substrates with a thin layer coating were subsequently washed and thermally treated at 723 K for 30 min to obtain. Fabrication of NiO/Poly(4-alkylthiazole) (PTzTNB and PTzTHX) Composite Photocathodes. Of PTzTHX with Mn = 29.6 A thin and compact PTzTNB kg or PTzTHX layer was spin-coated on as-obtained NiO electrodes at 600 rmp using corresponding poly(4-alkylthiazole) solution (5 mg mL−1 in chloroform). The EIS was documented at a direct current (DC) bias of 0.1 VRHE in the frequency range from 20 kHz to 0.2 Hz
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