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RuO 2 -NiO Nanosheets on Conductive Nickel Foam for Reliable and Regeneratable Seawater Splitting
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Water Splits To Degrade Two-Dimensional Group-IV Monochalcogenides in Nanoseconds
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Monolithic Photoelectrochemical Device for Direct Water Splitting with 19% Efficiency
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Potential-Sensing Electrochemical AFM Shows CoPi as a Hole Collector and Oxygen Evolution Catalyst on BiVO 4 Water-Splitting Photoanodes
Oxide/(oxy)hydroxide overlayers such as cobalt (oxy)hydroxide phosphate (CoPi) enhance the performance of BiVO 4 water-spitting photoanodes, but the mechanism of this enhancement remains unclear. Iin this work, we show that if the BiVO 4 layer is thin and incompletely covers an underlying conductive glass, the performance dramatically decreases as CoPi loading is increased. This is consistent with direct contact between the CoPi and conducting glass that leads to “shunt” recombination of photogenerated holes accumulated in the CoPi. For thicker BiVO4 layers that completely cover the conducting glass, these shunt pathways are blocked. We then use a nanoelectrode atomic force microscopy probe to measure, in operando, the electrochemical potential of CoPi on thick BiVO4 films under illumination. We find that CoPi is charged to a potential necessary to drive water oxidation at a rate consistent with the measured photocurrent. CoPi acts as a hole collector and is the principal driver of water oxidation on BiVO 4 .
Unconventional Relation between Charge Transport and Photocurrent via Boosting Small Polaron Hopping for Photoelectrochemical Water Splitting
Doping in semiconductor photoelectrodes controls defect formation and carrier transport that critically determine the device performance. Here we report an unconventional carrier transport relation that is tuned by extrinsic molybdenum (Mo) doping in BiVO 4 photoanodes. Using the single-crystalline thin film approach, we identify that Mo doping significantly condenses the optimization regime between carrier transport and photon collection. For Mo-doped BiVO 4 films, an unprecedentedly thin layer (50 nm), less than one-third of the pristine BiVO 4 thickness, delivers larger photocurrents by overcoming the charge transport limitation, representing a regime not covered in conventional models. We provide direct evidence that Mo doping improves electron transport by boosting not only the donor density but also the electron mobility in the form of a small polaron, with the latter applying substantial impact on the photoelectrochemical performance. Density functional theory calculations reveal that fully ionized Mo dopants establish a strong electrostatic interaction with a small polaron, which helps reduce its hopping barrier by minimizing the local lattice expansion. Here, our results deliver mechanistic insights on the interplay between extrinsic doping and carrier transport, and provide guidance in developing advanced semiconductor photoelectrodes.
Homochiral and Heterochiral Cation Mixing in 2D Perovskites for Enhanced Structural Asymmetry and Spin Splitting
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Atomistic Defect Makes a Phase Plate for the Generation and High-Angular Splitting of Electron Vortex Beams
Topological defects in solid-state materials by breaking the translational symmetry offer emerging properties that are not present in their parental phases. For example, edge dislocations—the 2π phase-winding topological defects—in antiferromagnetic NiO crystals can exhibit ferromagnetic behaviors. We study how these defects could give rise to topological orders when they interact with a high-energy electron beam. To probe this interaction, we formed a coherent electron nanobeam in a scanning transmission electron microscope and recorded the far-field transmitted patterns as the beam steps through the edge dislocation core in [001] NiO. Surprisingly, we found the amplitude patterns of the <020> Bragg disks evolve in a similar manner to the evolution of an annular solar eclipse. Using the ptychographic technique, we recovered the missing phase information in the diffraction plane and revealed the topological phase vortices in the diffracted beams. Through atomic topological defects, the wave function of electrons can be converted from plane wave to electron vortex. Technologically, this approach provides a feasible route for the fabrication of phase plates that can generate electron vortex beams with an angular separation that is three orders of magnitude larger than what traditional nanofabrication technology can offer. This advance will enable the collection of magnetic circular dichroism spectra with high spatial resolution and high efficiency, boosting the understanding of the relationship between symmetry breaking and magnetic property of individual topological defect at the atomic scale.
Solution-Processed BiI 3 Films with 1.1 eV Quasi-Fermi Level Splitting: The Role of Water, Temperature, and Solvent during Processing
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High-Throughput Experimental Study of Wurtzite Mn 1– x Zn x O Alloys for Water Splitting Applications
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