Insight into the Transition‐Metal Hydroxide Cover Layer for Enhancing Photoelectrochemical Water Oxidation

Abstract

Depositing a transition‐metal hydroxide (TMH) layer on a photoanode has been demonstrated to enhance photoelectrochemical (PEC) water oxidation. However, the controversial understanding for the improvement origin remains a key challenge to unlock the PEC performance. Herein, by taking BiVO4/iron‐nickel hydroxide (BVO/FxN4−x‐H) as a prototype, we decoupled the PEC process into two processes including charge transfer and surface catalytic reaction. The kinetic information at the BVO/FxN4−x‐H and FxN4−x‐H/electrolyte interfaces was systematically evaluated by employing scanning photoelectrochemical microscopy (SPECM), intensity modulated photocurrent spectroscopy (IMPS) and oxygen evolution reaction (OER) model. It was found that FxN4−x‐H acts as a charge transporter rather than a sole electrocatalyst. PEC performance improvement is mainly ascribed to the efficient suppression of charge recombination by fast hole transfer kinetics at BVO/FxN4−x‐H interface.

Plasmon‐Enhanced Charge Separation and Surface Reactions Based on Ag‐Loaded Transition‐Metal Hydroxide for Photoelectrochemical Water Oxidation

“…Then the chemical states of Co (Co 2+ and Co 3+ ) will be changed to Co 2−x and Co 3−x , and the low‐value states of Co are inclined to rapidly migrate photogenerated holes to the Co(OH) x surface and effectively inhibits interface recombination, as evidenced by the SPECM analysis (Figure 4b and S25, Supporting Information) and previous reports. [ 44,45 ] Meanwhile, the hot holes left behind on Ag nanoparticles to serve as electron trappers to effectively capture electrons from Co(OH) x [ 20 ] , boosting the oxidation of inactive Co II/III to active Co III/IV , and finally giving rise to the O 2 evolution, as proved by the OER (Figure 5) and I–t curves (Figure S29, Supporting Information) results.…”

Boosted charge transport through Au-modified NiFe layered double hydroxide on silicon for efficient photoelectrochemical water oxidation

“…3,25,26 However, the as-deposited oxides or hydroxide lms could contain natural defect sites of vacancies or various surface trap sites, increasing the recombination and trapping of charges and lowering the stability in strong alkaline electrolytes. [27][28][29][30][31][32] Also, the open-channel architecture of LDH cannot effectively passivate Si from corrosive aqueous solutions. 25,33 Therefore, an appropriate catalytic engineering strategy for existing LDHs with Si structures is necessary to overcome their overall PEC water oxidation limits.…”