A facile photoetching approach is described that alleviates the negative effects from bulk defects by confining the oxygen vacancy (Ovac) at the surface of BiVO4 photoanode, by 10‐minute photoetching. This strategy could induce enriched Ovac at the surface of BiVO4, which avoids the formation of excessive bulk defects. A mechanism is proposed to explain the enhanced charge separation at the BiVO4 /electrolyte interface, which is supported by density functional theory (DFT) calculations. The optimized BiVO4 with enriched surface Ovac presents the highest photocurrent among undoped BiVO4 photoanodes. Upon loading FeOOH/NiOOH cocatalysts, photoetched BiVO4 photoanode reaches a considerable water oxidation photocurrent of 3.0 mA cm−2 at 0.6 V vs. reversible hydrogen electrode. An unbiased solar‐to‐hydrogen conversion efficiency of 3.5 % is realized by this BiVO4 photoanode and a Si photocathode under 1 sun illumination.
This paper describes a bifacial passivation strategy for the metal/Si interface of metal–insulator–semiconductor (MIS) photoelectrodes, achieving record high activities for water oxidation and reduction for Si-based MIS electrodes.
Terahertz radiation generation from liquid water has long been considered to be impossible due to strong absorption. A few very recent works reported terahertz generation from water, but the mechanism is not clear and the efficiency demands to be enhanced. We show experimentally that strong single-cycle terahertz radiation with field strength of 0.2 MVcm −1 is generated from a water line/column of ∼ 200µm in diameter irradiated by a mJ femtosecond laser beam. This strength is 100-fold higher than that produced from air. We attribute the mechanism to the laser-ponderomotive-force-induced current with the symmetry broken around the water-column interface. This mechanism can explain our following observations: the radiation can be generated only when the laser propagation axis deviates from the column center; the deviation determines its field strength and polarity; it is always p-polarized no matter whether the laser is p-or s-polarized.This study provides a simple and efficient scheme of table-top terahertz sources based on liquid water.
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