Dual Modification of a BiVO₄ Photoanode for Enhanced Photoelectrochemical Performance

Abstract

Bismuth vanadate (BiVO ) has triggered extensive interest in photoelectrochemical (PEC) water splitting, owing to its narrow band gap and sufficiently positive valence band. However, some defects still exist to block the solar utilization efficiency and hydrogen evolution kinetics. Herein, the NiMoO semiconductor is combined with a BiVO photoanode, for the first time, and excellent PEC performance is achieved on the basis of heterojunction formation and favorable conductivity of NiMoO . In addition, it has been demonstrated that NiMoO promotes the light absorption ability, charge separation efficiency, and surface charge-transfer efficiency comprehensively. To further improve the photoconversion efficiency, cobalt phosphate, as an oxygen evolution reaction cocatalyst, is deposited on the above electrode and achieves a much enhanced utilization efficiency of 1.18 %, with a photocurrent density of 5.3 mA cm at 1.23 V versus a reversible hydrogen electrode; this exceeds most results reported to date. This rational and unique photoanode construction provides a new thread for the photoelectrode designation.

Rationally Designed Heterojunction on a CuBi2O4 Photocathode for Improved Activity and Stability during Photoelectrochemical Water Reduction

“…The ratio of hydrogen to oxygen is close to that of stoichiometry 2 : 1, and Faraday efficiency is calculated at about 90 %. In the Mott-Schottky (MÀ S) curve, the x-intercept determines the flat band potential and the linear slope determines the carrier concentration, [30] and the MÀ S curve was obtained under dark conditions at 1k Hz frequency. The slopes of the MÀ S curves of CBO, CBO/ZS and CBO/ZS/P25 are all negative ( Figure S6a, S6b and S6c), explaining that they are all p-type semiconductors.…”

The Synergetic Benefits of Passivation Layer and Catalytic Layer on Hematite for Efficient Water Splitting

“…To further prove that the charge injection efficiency of the photoanode is increased, 0.5 m H 2 O 2 was added in electrolyte, for H 2 O 2 is a well‐known hole scavenger [15c,21]. The injection efficiency in Figure b is achieved through dividing photocurrent by photocurrent . It can be seen that the charge injection efficiency of the Fe 2 O 3 /FeOOH photoanode is two times higher than that of the pristine hematite over the entire potential range.…”

“…[15c,21] The injection efficiency η surf in Figure 8b is achieved through dividing J H 2 O photocurrent by J H 2 O 2 photocurrent. [22] It can be seen that the charge injection efficiency of the Fe 2 O 3 /FeOOH photoanode is two times higher than that of the pristine hematite over the entire potential range. It proves that FeOOH is an efficient oxygen evolution catalyst.…”

Hybrid photoanodes for water oxidation combining a molecular photosensitizer with a metal oxide oxygen-evolving catalyst

“…Intense researches are devoted to the development of photoelectrodes solely based on inorganic semiconductor (SC) materials, 2,7,11,15 but they face the difficulty of having a SC that can both effectively absorb visible light and display conduction and valence bands (denoted CB and VB, respectively) with adequate energy levels to catalyze OER for photoanodes and HER for photocathodes. Some PECs using SCs based on metal oxides (WO 3 , BiVO 4 , Fe 2 O 3 and CuBi 2 O 4 ) 4,7,[20][21][22][23][24] or oxynitrides (TaON, LaTiO 2 N and SrNbO 2 N) [25][26][27][28] for the photoanodes, and on p-type chalcogenides (CdTe, CuIn 1-x Ga x Se 2 ) 29,30 or metal oxides (p-Cu 2 O) [31][32][33][34] for the photocathodes, do operate under visible light. Nevertheless their STH conversion efficiency remains below 10%, the threshold for commercial applications.…”