Photo‐Electrochemical Glycerol Conversion over a Mie Scattering Effect Enhanced Porous BiVO ₄ Photoanode

Abstract

Bismuth vanadate (BiVO 4 ), with a bandgap of ≈2.4 eV, can harvest light in the waveband below 520 nm and thus has a theoretical photocurrent density of ≈7.5 mA cm −2 under one sun illumination. However, the short hole-diffusion length (<70 nm) of BiVO 4 is an intrinsic limitation that leads to poor charge separation efficiency. Therefore, considerable efforts have been devoted to addressing this issue in recent decades. [11][12][13][14][15] To date, the porous BiVO 4 (P-BiVO 4 ) film reported by Kim and Choi, which comprises several tens or hundreds of nanometers of particles that can remarkably reduce the hole-diffusion distance, has been regarded as a promising thin-film model for PEC conversion. [16] In recent years, research on the PEC performance of the P-BiVO 4 film has undergone a spur of activity, aided by various successful strategies, including vacancy engineering [17][18][19][20][21][22] and cocatalyst loading, [23][24][25][26] which resulted in a charge separation efficiency of up to 90%. However, P-BiVO 4 films generally present poor light absorbability compared to BiVO 4 films composed of micrometer-sized particles. It is well-known that multiple optical phenomena, including reflection, scattering, and transmission, occur simultaneously when incident photons interact with the photoelectrode and together determine the light absorbability of the photoelectrode. Although a porous structure reduces the specular reflection, the scattering effect of a porous structure is The photo-electrochemical (PEC) oxidation of glycerol (GLY) to high-valueadded dihydroxyacetone (DHA) can be achieved over a BiVO 4 photoanode, while the PEC performance of most BiVO 4 photoanodes is impeded due to the upper limits of the photocurrent density. Here, an enhanced Mie scattering effect of the well-documented porous BiVO 4 photoanode is obtained with less effort by a simple annealing process, which significantly reduces the reflectivity to near zero. The great light absorbability increases the basic photocurrent density by 1.77 times. The selective oxidation of GLY over the BiVO 4 photoanode results in a photocurrent density of 6.04 mA cm −2 and a DHA production rate of 325.2 mmol m −2 h −1 that exceeds all reported values. This work addresses the poor ability of nanostructured BiVO 4 to harvest light, paving the way for further improvements in charge transport and transfer to realize highly efficient PEC conversion.

Probing and Modulation of the Electric Double Layer at the Insulating Oil–Paper Interface

“…Converter transformers insulated with oil and paper must be able to withstand complex electrical stresses, including polarity reversal, pulses of direct current (DC) superimposed on alternating current (AC) pulses, and AC superimposed on DC pulses. , Excessive charges excited by the applied voltage are hindered by the interface barrier caused by EDL due to the scattering effect , and accumulated at the oil–paper interface. Therefore, it is necessary to explore EDL regulation methods to reduce the charge accumulation at the oil–paper interface under applied voltages and avoid possible partial discharge and insulation degradation.…”

Imperfect makes perfect: defect engineering of photoelectrodes towards efficient photoelectrochemical water splitting

“…Chemical reduction is one of the most effective methods to design semiconductor surface defects by using various reducing solvents such as glycol and glycerol or reducing agents such as sodium borohydride, phosphite, hydrazine hydrate, etc. [117][118][119][120][121] For example, Ni 3 S 2 , NiS, Ni 3 S 4 and NiS 2 (from nickelrich to sulfur-rich) in the nickel sulfide system are excellent electrocatalysts due to their low band gap and electrical conductivity, and a novel bimetallic (Ni, In)(O, S) 2Àx nanosheet catalyst system was prepared by hydrazine reduction to generate active oxygen vacancies, which can enhance charge transport and separation. 122 Similarly, sulfur vacancy-enriched ZnIn 2 S 4 was fabricated through the formation of sulfur vacancies by the addition of hydrazine hydrate (Fig.…”

“…So far, many photoelectrode materials have been widely studied, such as TiO 2 , 117 ZnO, 39 α-Fe 2 O 3 , 143 WO 3 , 82 BiVO 4 , 118 SrTiO 3 , 38 g-C 3 N 4 , 121 TaON 144 and Ta 3 N 5 . 145 At the initial stage of PEC water splitting, research efforts are mainly concentrated on TiO 2 .…”

Unravelling the Superior Photoelectrochemical Water Oxidation Performance of the Al-Incorporated CoOOH Cocatalyst-Loaded BiVO4 Photoanode

“…BiVO 4 is an n-type semiconductor with a narrow band gap (∼2.4 eV) and a suitable valence band position for water oxidation. Moreover, it is able to absorb 11% of the solar spectrum, resulting in a high theoretical photocurrent density of ∼7.6 mA cm –2 yielding a solar-to-hydrogen conversion efficiency of 9.3%. − However, the energy conversion efficiency is affected by slow oxidation kinetics, indolent photoinduced charge separation, and reduced charge-carrier mobility due to the lack of connectivity of VO 4 tetrahedra. − In addition to the water oxidation kinetics, the PEC stability is another key factor for determining the performance of photoanodes in practical applications. Also, the electrode/electrolyte interface of BiVO 4 photoanodes is susceptible to both photocorrosion and film dissolution.…”