Band Structure Engineering toward Low-Onset-Potential Photoelectrochemical Hydrogen Production

Abstract

Photoelectrochemical (PEC) hydrogen production can directly and effectively convert solar energy to clean and sustainable hydrogen energy. However, taking the photoanode as an example, the onset potential (V onset) of the photoanodic current is too positive, which is not conducive to the improvement of energy conversion efficiency and thus hinders the practical application of PEC hydrogen production. Here, we demonstrate a new quaternary alloy nanowire photoanode with low V onset and high solar conversion efficiency constructed by a narrow-bandgap semiconductor CdSeTe and a wide-bandgap semiconductor CdS, a strategy that enables the energy band modulation by adjusting the molar ratio of the two semiconductors. Through the modulation of the band structure, the negative shift in the V onset of the PEC hydrogen production can be realized, so that high photocurrent is achieved under a lower bias voltage. As a result, we cathodically shifted the V onset by 0.7 VRHE on the alloyed cadmium-based chalcogenide photoanode under 1-sun light. This strategy of using energy band modulation to achieve a lower V onset and high energy conversion efficiency will provide more possibilities for the industrial application of PEC hydrogen production.

Controlled Band Offsets in Ultrathin Hematite for Enhancing the Photoelectrochemical Water Splitting Performance of Heterostructured Photoanodes

“…36,37 Furthermore, research studies on band-gap engineering through controlling the thickness have been conducted for enhancing the water splitting performance. 38 The motivation of this work is to deepen our understanding of the effect of thickness on change in the energy band and PEC properties of the Fe 2 O 3 -based heterostructure. Here, we report the PEC performance of thin and thick Fe 2 O 3 overlayers on the BVO/WO 3 nanorod heterostructure photoanodes deposited on fluorine-doped tin oxide (FTO) glass, especially focusing on the change in the energy band diagram in the heterostructures.…”

“…For example, the BVO/WO 3 heterostructure has been frequently studied and the studies show the enhancement of light absorption, charge separation ability, and conversion efficiency. − Additionally, nanostructuring the photoanodes is beneficial due to their large active surface areas and short charge transport pathways. − Therefore, introducing a nanostructured type II heterojunction to the PEC cell would be a good strategy to improve PEC water splitting performance. In recent decades, investigation of the size effect has been of interest for the discovery of the way to develop highly efficient catalysts such as the quantum size effect that can increase the stored free energy and enhance the charge-transfer rate. , Furthermore, research studies on band-gap engineering through controlling the thickness have been conducted for enhancing the water splitting performance …”

Improvement of microporous silicoaluminophosphate properties by Fe and Ti insertion for photocatalytic hydrogen generation under visible light

“…2 H2O + 2 e -→ H2 +2 OH -E= -0.14 V (-0.16 V) vs. SCE for FAPSO4-5 (FTAPSO4-5) Moreover, we can see from the CV curves that FAPSO4-5 presents a lower onset potential Von (-0.36 V) compared with FTAPSO4-5(-0.08 V), which allows us to predict a better photocatalytic activity for FAPSO4-5 [66].…”

Phosphorus-Doped Single-Crystalline Quaternary Sulfide Nanobelts Enable Efficient Visible-Light Photocatalytic Hydrogen Evolution

“…The corresponding band-gap energy decreases from 2.23 eV (CZIS nanobelts) to 2.16 eV (CZIS-P nanobelts) after P doping. Based on previous research, the obvious red-shifted absorption has been explained as evidence of the band trailing effects corresponding to the disorder generated by dopant insertion into the CZIS lattice. ,, We further used ultraviolet photoelectron spectroscopy (UPS) to study the band structure of CZIS-P nanobelts. − The work functions are calculated to be 4.38 and 4.19 eV according to the formula Φ = hν – E onset (Figure d, where hν represents the utilized photon energy of 21.2 eV, E onset is the onset level, and Φ is the work function). Figure e shows the valance band maxima (VBM) of CZIS-P and CZIS nanobelts located at 0.44 and 0.84 eV below the Fermi level, respectively.…”