Reinforcement of Visible-Light Harvesting and Charge-Transfer Dynamics of BiVO₄ Photoanode via Formation of p–n Heterojunction with CuO for Efficient Photoelectrocatalytic Water Splitting

Abstract

High photoinduced charge recombination process and indolent water oxidation kinetics are major drawbacks of the bismuth vanadate (BiVO4) photoanode in photoelectrocatalytic (PEC) water splitting. To address these issues, a bismuth vanadate/copper oxide (BiVO4/CuO) p–n junction electrode was fabricated via the electrodeposition method, and its PEC performance was studied using 0.1 M potassium phosphate (KPi) as an electrolyte under AM 1.5G (100 mW cm–2) irradiation. At an optimized condition, the BiVO4/CuO p–n junction electrode showed improvement in the current density of 2.05 mA cm–2 at +1.23 VRHE, which was ∼2-fold higher than the BiVO4 electrode (0.99 mA cm–2). The applied bias photon-to-current efficiency (ABPE) of the BiVO4/CuO electrode was also ∼2.5-fold higher than the BiVO4 electrode. Loading of CuO over the BiVO4 surface improved the light absorption ability of the electrode in the entire UV–vis region, leading to generation of a greater number of photoinduced charge carriers, and it also enhanced the reactive sites for water oxidation as per the calculation of double-layer capacitance (C dl). The formation of inner electric field (IEF) at the interface between BiVO4 and CuO offered well-separated electron–hole pairs in association with improvement in the lifetime of charge carriers, and as a consequence, the BiVO4/CuO electrode showed a transient decay time of 4.45 s, which was ∼1.6-fold higher than the BiVO4 electrode (2.81 s). The formation of p–n junction between BiVO4 and CuO significantly reduced the charge transfer resistance (R ct) at the electrode/electrolyte interface (EEI), and as a result, the BiVO4 and BiVO4/CuO electrodes show R ct values of 454.4 and 201.9 Ω, respectively, under light illumination. Moreover, the Bode phase analysis confirmed quick hole consumption in the presence of the BiVO4/CuO electrode over the pristine BiVO4 electrode during water oxidation process. Overall, the formation of a p–n junction facilitated well-separated electron–hole pairs and improved the hole transfer at the EEI for an efficient PEC water oxidation process.

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

“…The BiVO 4 /Al-CoOOH electrode delivers a higher C dl (99 μF cm –2 ), which is ∼1.4-fold and ∼2.2-fold higher than those of BiVO 4 /CoOOH (69 μF cm –2 ) and BiVO 4 electrode (44.5 μF cm –2 ), respectively (Figure S10). These results show the improvement of the active surface area and enriched the active sites after the Al doping for water oxidation. ,, Overall, the results suggest that the loading of CoOOH over BiVO 4 improved the overall PEC performance by reducing the charge recombination, improving the charge transfer at the EEI, and enhancing the water oxidation kinetics, and these factors are further improved by the incorporation of Al into CoOOH. Besides, the effect of Al on CoOOH toward the OER was further studied by first-principles calculations.…”

“…These results show the improve-ment of the active surface area and enriched the active sites after the Al doping for water oxidation. 2,49,50 Overall, the results suggest that the loading of CoOOH over BiVO 8a and in Table 2. The largest free-energy barrier is considered as a rate-determining step (RDS) and the theoretical overpotential η OER for an electrocatalyst is determined from the RDS; in both cases, the conversion of *OOH → O 2 is an RDS.…”

Lead‐Free Bismuth‐Based Halide Perovskites with Excellent Stability for Visible‐light‐Driven Photoelectrochemical Water Splitting

“…Where E F is the Fermi level obtained from the Mott–Schottky analysis, E VB(XPS) is the value obtained from the XPS valence band analysis and E g is the bandgap of the material [46,47] . On the basis of the calculation, the Cs 2 AgBiCl 6 electrodes shows the VBM and CBM of 2.13 V and −0.58 V respectively.…”

Enhanced Photoelectrocatalytic Water Splitting in Bi2Mo1–xWxO6 Solid Solutions: Understanding the Atomic Level Mechanism from the Experimental and First-Principles Approach

“…The overall PEC efficiency of photoelectrodes depends on several factors such as visible light absorption, charge transfer dynamics, and the lifetime of the charge carriers. − In PEC water splitting, water oxidation is a sluggish process and is considered a rate-determining step; therefore, the development of a photoanode is a crucial part in PEC water splitting. − Mostly, TiO 2 -based photoanodes were investigated in the PEC process due to their availability, stability, and harmlessness, but their wide bandgap (∼3.2 eV) makes them inefficient for harvesting solar energy; therefore, researchers focus on the development of semiconductor materials with a narrow bandgap (<3.0 eV). Recently, bismuth-based semiconductor materials such as BiOX (X = I, Cl, Br) , and Bi x M y O z (M = V, Mo, W, Fe) have attracted a lot of attention in the field of PEC water splitting due to their narrow bandgap, in which the valence band consisting of O-2p and Bi-6s orbitals offers a well-dispersed valence band and facilitates the mobility of the photogenerated holes for water oxidation. − Compared to BiVO 4 , Bi 2 MoO 6 and Bi 2 WO 6 have a higher positive valence band edge, and hence, they can expect facile water oxidation by photogenerated holes in PEC water splitting. Moreover, Bi 2 MoO 6 (∼2.6 eV) has a similar bandgap value to BiVO 4 (∼2.4 eV).…”