General and Robust Photothermal‐Heating‐Enabled High‐Efficiency Photoelectrochemical Water Splitting

Abstract

However, its STH efficiency is greatly plagued by its limited light absorption, poor charge transport, and sluggish water oxidation kinetics. [2] In this context, recent research has focused on overcoming these intrinsic issues, including N 2 or H 2 treatment for improved light harvesting, [3] heteroatom doping for increasing charge carrier densities and thus charge transport, [4] and oxygen evolution cocatalyst (OEC) loading for facilitating the reaction kinetics. [5] Despite the effectiveness of the above methods, a simple route to synchronously improve the three processes for enhanced PEC photoanode performance of photoanode is highly desirable. This has yet to be largely explored.The operation temperature has been proven to be exert a profound influence on the bandgap of semiconductors, hole diffusion length of photoanodes and electrocatalytic properties of OECs. [6] For example, the absorption band of semiconductor quantum dots was found to exhibit a red shift with increasing temperature. [7] Minority carrier hopping was activated within BVO photoanodes via a moderate temperature elevation of the electrolyte, resulting in efficient bulk charge separation. [8] Furthermore, the electrocatalytic performance of OECs could be greatly enhanced by magnetic heating in an external high-frequency alternating magnetic field. [9] Inspired by the above intriguing results, it The ability of photoanodes to simultaneously tailor light absorption, charge separation, and water oxidation processes represents an important endeavor toward highly efficient photoelectrochemical (PEC) water splitting. Here, a robust strategy is reported to render markedly improved PEC water splitting via sandwiching a photothermal Co 3 O 4 layer between a BiVO 4 photoanode film and an FeOOH/NiOOH electrocatalyst sheet. The deposited Co 3 O 4 layer manifests compelling photothermal effect upon near-infrared irradiation and raises the temperature of the photoanodes in situ, leading to extended light absorption, enhanced charge transfer, and accelerated water oxidation kinetics simultaneously. The judiciously designed NiOOH/ FeOOH/Co 3 O 4 /BiVO 4 photoanode renders a superior photocurrent density of 6.34 mA cm -2 at 1.23 V versus a reversible reference electrode (V RHE ) with outstanding applied bias photon-to-current efficiency of 2.72% at 0.6 V RHE . In addition to the metal oxide, a wide variety of metal sulfides, nitrides, and phosphides (e.g., CoS, CoN, and CoP) can be exploited as the heaters to yield high-performance BiVO 4 -based photoanodes. Apart from BiVO 4 , other metal oxides (e.g., Fe 2 O 3 and TiO 2 ) can also be covered by photothermal materials to impart significantly promoted water splitting. This simple yet general strategy provides a unique platform to capitalize on their photothermal characteristics to engineer high-performing energy conversion and storage materials and devices.

Pt‐Induced Defects Curing on BiVO4 Photoanodes for Near‐Threshold Charge Separation

“…The ratio of κ trans /(κ trans + κ rec ), which can evaluate the charge transfer efficiency, could be shown by comparing the instantaneous photocurrent and steady‐state photocurrent. [ 17,41 ] From Figure 2f, the higher κ trans values are attained for the BiVO 4 samples after photoactivation from 6 to 20 h compared to that of the as‐prepared BiVO 4 sample, along with the lower κ rec values (Figure 2g). The BVO with 6 h photoactivation shows the highest κ trans value and the lowest κ rec value with the highest charge transfer efficiency, implying that the surface recombination is significantly reduced by the surface passivation of the oxygen vacancies.…”

Polypyrrole Serving as Multifunctional Surface Modifier for Photoanode Enables Efficient Photoelectrochemical Water Oxidation

“…Furthermore, the applied bias photon-to-current efficiency (ABPE) values of CIS, CIS/ Ni, CIS/PPy, and CIS/Ni-PPy photoanodes in Figure S14 (Supporting Information) are calculated to further clarify the role of NIR light in the PEC water splitting system. [21] Apparently, the photothermal effect promotes the ABPE, and the CIS/Ni-PPy photoanode achieves the highest ABPE value of 1.98% at 0.70 V RHE under AM 1.5G + NIR illumination. The photothermal effect shifts the maximum ABPE of the photoanode to a lower bias than that of the photoanode in the absence of NIR irradiation, indicating the photothermal effect mainly plays a role in the low bias region.…”

“…The influence of photothermal effect on L p is evaluated by following formulation based on the Gärtner model. [21,39,40] ln 1…”

“…Moreover, when heating, electrolyte would evaporate and affect the stability of the entire PEC system. [21] Thus, it is urgent to introduce a strategy that can heat the photoanode targetedly to elevate its temperature while makes no difference to the electrolyte. Liu and coworkers designed a composite NiOOH/ FeOOH/Co 3 O 4 /BiVO 4 photoanode to utilize the photothermal effect in PEC water splitting.…”

“…Liu and coworkers designed a composite NiOOH/ FeOOH/Co 3 O 4 /BiVO 4 photoanode to utilize the photothermal effect in PEC water splitting. [21] Photothermal Co 3 O 4 layer raises the temperature of BiVO 4 photoanode, resulting in simultaneous improvement of light absorption, charge transfer, and water oxidation reaction kinetics. However, this modification strategy still relies on multiple processing, and the surface photocatalytic activity depends on the subsequent coverage of the OER cocatalyst NiOOH/FeOOH, which may lead to additional reaction barriers.…”