Highly Enhanced Photoelectrochemical Water Oxidation Efficiency Based on Triadic Quantum Dot/Layered Double Hydroxide/BiVO₄ Photoanodes

Abstract

The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is ∼1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.

Promoting charge carrier utilization by integrating layered double hydroxide nanosheet arrays with porous BiVO4 photoanode for efficient photoelectrochemical water splitting

“…This value is higher than other OECs decorated on un-doped BiVO4 (Table S2) and some photoanodes decorated with NiFe-LDH as OECs, e.g., NiFe-LDH/Ta3N5 (1.7 mA cm −2 at 1.23 V vs. RHE) [26], TiO2/rGO/NiFe-LDH (1.74 mA cm −2 at 1.245 V vs. RHE) [5], Mn-doping Fe2O3/NiFe-LDH (ca. 2.1 mA cm −2 at 1.23 V vs. RHE) [9], quantum dot/LDH/BiVO4 (2.23 mA cm −2 at 1.23 V vs. RHE) [17]. It is even comparable to the porous BiVO4 photoanode decorated with FeOOH/NiOOH dual OECs (4.2 mA cm −2 at 1.23 V vs. RHE) [13].…”

“…Therefore, exploring the appropriate semiconductors as photon absorbers and the highly efficient LDHs as OECs to fabricate photoanodes for efficient and stable PEC water splitting becomes highly desirable. Very recently, a triadic quantum dot/LDH/BiVO4 photoanode with enhanced PEC water oxidation (2.23 mA cm −2 at 1.23 V vs. RHE) has been reported by Xiang's group [17]. Nevertheless, the LDH/BiVO4 composite photoanode without sensitization of the quantum dots shows less improvement in photocurrent density compared with the pristine BiVO4.…”

“…Among them, BiVO4 is the top performer due to its relatively small band gap, adequate conduction band edge position and moderate charge transport properties [13][14][15][16][17][18]. However, the low charge separation efficiency and slow oxygen evolution kinetics of the unmodified BiVO4 need to be improved.…”

Recent Advances in Bismuth‐Based Nanomaterials for Photoelectrochemical Water Splitting

“…[76] Although BiVO 4 has as uitable band gap, it showsl ow incident photon-to-electron conversion efficiency (IPCE) at low voltages as ar esult of an increased recombination rate. [82][83][84] In the past five years, as ignificant amount of researchh as been directed towards BiVO 4 as ah ighly efficient visible-light photoelectrocatalyst, and this is covered in various review articles. Effortsh ave been madet oa ddress these issues either by improving the fabrication method or by utilizing various morphologies.…”

Enhancing Light-Driven Production of Hydrogen Peroxide by Anchoring Au onto C3N4 Catalysts

“…The reason for this is that the positive shift of the conduction band of C 3 N 4 improved the two-electron reduction of dioxygen to H 2 O 2 . Additionally, the MMO plays the role of the water oxidation catalyst (WOC), which has been recognized to be active in oxygen-evolving reactions [27][28][29]. Furthermore, the H 2 O 2 production was increased on the carbon-modified g-C 3 N 4 , which regulates the energy levels and is more suitable for the selective two-electron reduction of oxygen by photo-generated electrons [30].…”