Zhuo Xing

Efficient enhancement of hydrogen production by Ag/Cu2O/ZnO tandem triple-junction photoelectrochemical cell

Highly efficient semiconductor photoelectrodes for solar hydrogen production through photocatalytic water splitting are a promising and challenge solution to solve the energy problems. In this work, Ag/Cu2O/ZnO tandem triple-junction photoelectrode was designed and prepared. An increase of 11 times of photocurrent is achieved in the Ag/Cu2O/ZnO photoelectrode comparing to that of the Cu2O film. The high performance of the Ag/Cu2O/ZnO film is due to the optimized design of the tandem triple-junction structure, where the localized surface Plasmon resonance of Ag and the hetero-junctions efficiently absorb solar energy, produce, and separate electron-hole pairs in the photocathode.

Efficient enhancement of solar-water-splitting by modified "Z-scheme" structural WO3- W-Si photoelectrodes

N-type WO3 and p-type Si can be assembled into a composite structure called “Z-scheme,” which is a high efficiency model for overall water splitting. However, due to the existence of Schottky barrier, its relatively low photocurrent density is still a great challenge for application. Here, a modified “Z-scheme” structure by inserting a W interlayer is presented. A great enhancement of photocurrent density over 10 times is achieved, which can be ascribed to the introduction of the ohmic contacts between W interlayer with both WO3 and Si layers and the elimination of Si-O bands at the interface.

Cathodic shift of onset potential for water oxidation of WO3 photoanode by Zr+ ions implantation

Tungsten trioxide is one of the most widely studied semiconductors for photoelectrochemical water splitting. However, its onset potential is too positive. In a photoelectrochemical system, a low onset potential and a high photocurrent for a photoanode are important for enhancing the efficiency of water splitting. It is an effective way to adjust the onset potential by changing the conduction and valence band level. Doping is a powerful way to alter the positions of the energy levels of semiconductors to improve their photoelectrochemical performance. In this paper, we present a method of ion implantation to alter the energy levels by implanting Zr+ ions into WO3. Cathodic shifts of the photocurrent onset potential for water oxidation are achieved. The systematic studies show that ion implantation followed by thermal annealing treatment can form substitutional Zr4+ in WO3. The upward shifts of the conduction band and valence band lead to the cathodic shifts of the onset potential. Two combined factors lead...

Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO 2 and TiO 2 passivation layers

Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO2/nanoporous-Si and the TiO2/nanoporous-Si by I–V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO2/nanoporous Si are lower than that of the HfO2/nanoporous Si, the former is more stable than the later.

Multifunctional Vanadium-doped Cobalt Oxide Layer on Silicon Photoanodes for Efficient and Stable Photoelectrochemical Water Oxidation

Photoelectrochemical (PEC) water splitting is an attractive method to convert solar energy into chemical fuel. However, developing highly efficient photoanodes for PEC cells to meet industrial requirements remains a challenge. Herein, we effectively alter the onset potential of a photoanode though the doping of V into Co oxide film via the low-cost method of magnetron co-sputtering deposition on a p+n junction Si cell (p+nSi/CoVO). The highest photocurrent density of p+nSi/CoVO is 29.15 mA cm−2 (at 1.23 V vs. a reversible hydrogen electrode (RHE)). Moreover, a successful decrease in the onset potential by 40 mV to 1.00 V (at 1 mA cm−2) and a 3.6-fold increase in the incident photon to current conversion efficiency (IPCE) are achieved compared to p+nSi/CoO. The p+n junction Si cell provides not only photoexcited vacancies but also a photoproduced voltage of 608 mV. We find that the doped V atoms are multifunctional: they can decrease the charge transfer resistance of the Co3O4 film, serve as a Lewis acid to increase the local pH value, and facilitate the generation of oxo-bridged CoIVO species to accelerate the kinetics of the oxygen evolution reaction (OER); therefore, they can obviously decrease the onset potential of p+nSi/CoVO in the OER. This work highlights a general approach to further improve the performance of OER catalysts via engineering active sites and the local chemical environment through element doping.