We herein demonstrate the unusual effectiveness of two strategies in combination to enhance photoelectrochemical water splitting. First, the work function adjustment via molybdenum (Mo) doping significantly reduces the interfacial energy loss and increases the open-circuit photovoltage of bismuth vanadate (BiVO4) photoelectrochemical cells. Second, the creation and optimization of the heterojunction of boron (B) doping carbon nitride (C3N4) and Mo doping BiVO4 to enforce directional charge transfer, accomplished by work function adjustment via B doping for C3N4, substantially boost the charge separation of photo-generated electron-hole pairs at the B-C3N4 and Mo-BiVO4 interface. The synergy between the above efforts have significantly reduced the onset potential, and enhanced charge separation and optical properties of the BiVO4-based photoanode, culminating in achieving a record applied bias photon-to-current efficiency of 2.67% at 0.54 V vs. the reversible hydrogen electrode. This work sheds light on designing and fabricating the semiconductor structures for the next-generation photoelectrodes. While photoelectrodes represent a promising solar-to-fuel conversion technology, material challenges limit performances. Here, authors improve the onset potential and charge separation of bismuth vanadate photoanode water splitting performances by work function tuning and heterojunction engineering.

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Enhancing photoelectrochemical water splitting by combining work function tuning and heterojunction engineering.

BiOI–BiVO4 photoanodes with significantly improved solar water splitting capability: p–n junction to expand solar adsorption range and facilitate charge carrier dynamics

Water splitting technology directly stores solar energy into the chemical bonds of diatomic hydrogen to be used as a clean fuel without producing any unwanted side reactions, byproducts or environmentally polluting compounds. Semiconductor materials are needed for a photoelectrochemical (PEC) device to catalytically convert photons from sunlight into chemical energy. Materials implemented in a device for sustainable hydrogen production are required to be inexpensive, highly photo-active, chemically stable, environmentally sustainable, and have a high solar-to-hydrogen conversion efficiency. Although many semiconductor composites and nanostructures have been examined, thus far, no material satisfies all criteria of an implementable photocatalyst and many materials do not show necessary energy conversion efficiency. Materials that depicted a high efficiency often rely on the ultraviolet portion of the solar spectrum, which does not contain enough energy for the industrial utilization of PEC water splitting technologies. Focusing on the use of the visible spectrum is promising for hydrogen production. Herein, recent advancements in the activity of visible light semiconductors are presented, including both platinum and non-platinum group materials. This review touches on the latest developments in various synthesis schemes capable of achieving suitable water splitting compositions and architectures while highlighting the challenges being faced when designing visible light-active water splitting photocatalysts. Interesting advancements in the use of nanostructures for designing the next generation of catalysts will be discussed. Also, for the proper comparison of catalytic efficiencies, it is important to establish terminology that can compare data across a magnitude of experimental conditions. A notable challenge associated with the catalysis is its stability or photocorrosion, which lacks established protocols. Promising future directions for designing next generation materials are discussed.

Recent advancements in semiconductor materials for photoelectrochemical water splitting for hydrogen production using visible light

The leaf-like structure BiVO4 electrode and MFe2O4/BiVO4 (M = Ni, Co) composite photoelectrodes were prepared by electrochemical deposition, ensuing heating treatment and electrophoretic deposition technology The characterizations of SEM, XRD and DRS indicated that the BiVO4 derivatives mainly existed in small nanoparticles with monoclinic phase and exhibited stronger light absorption capability than that of pure BiVO4 Hereon, the respective photoelectrochemical (PEC) activities of BiVO4 and its derived composites were systematically studied The results suggested that the NiFe2O4/BiVO4 and CoFe2O4/BiVO4 not only showed higher photocurrent response values at 123 V vs NHE than pure BiVO4 electrode under visible light illumination, but also played a superior PEC hydrogen evolution performance, which was considered owing to their strong absorption to light, reduction combination of carriers and effective separation of electrons and holes

Yongjie Zhu

Papers

NiO decorated Mo:BiVO4 photoanode with enhanced visible-light photoelectrochemical activity

enhanced visible-light photoelectrochemical activity