Cobalt Hexacyanoferrate on BiVO₄ Photoanodes for Robust Water Splitting

Abstract

The efficient integration of photoactive and catalytic materials is key to promoting photoelectrochemical water splitting as a sustainable energy technology built on solar power. Here, we report highly stable water splitting photoanodes from BiVO4 photoactive cores decorated with CoFe Prussian blue-type electrocatalysts (CoFe-PB). This combination decreases the onset potential of BiVO4 by ∼0.8 V (down to 0.3 V vs reversible hydrogen electrode (RHE)) and increases the photovoltage by 0.45 V. The presence of the catalyst also leads to a remarkable 6-fold enhancement of the photocurrent at 1.23 V versus RHE, while keeping the light-harvesting ability of BiVO4. Structural and mechanistic studies indicate that CoFe-PB effectively acts as a true catalyst on BiVO4. This mechanism, stemming from the adequate alignment of the energy levels, as showed by density functional theory calculations, allows CoFe-PB to outperform all previous catalyst/BiVO4 junctions and, in addition, leads to noteworthy long-term stability. A bare 10–15% decrease in photocurrent was observed after more than 50 h of operation under light irradiation.

Rational Design and Construction of Cocatalysts for Semiconductor‐Based Photo‐Electrochemical Oxygen Evolution: A Comprehensive Review

“…Besides, Hegner et al [263] deposited CoFe prussian blue-type cocatalysts (CoFe-PB) onto BiVO 4 photoelectrode (Figure 21c), resulting in a 6 times increment of IPCE at the same wavelength and a decrease of ≈15% of stability over 50 h irradiation Adv. Sci.…”

A Noble‐Metal‐Free Heterogeneous Photosensitizer‐Relay Catalyst Triad That Catalyzes Water Oxidation under Visible Light

“…[10][11][12][13][14][15][16][17][18][19] Although the use of robust heterogeneous assemblies such as oxides could be apromising solution to improve stability,the lack of complete control on the coordination of metal ions in oxide chemistry does not allow the preparation of oxidebased dyads. [22][23][24][25][26][27][28][29][30][31] PBAs consist of earth-abundant elements,perform at relatively low overpotentials (< 500 mV for ac urrent density of 1mAcm À2 ), exhibit exceptional stabilities in awide pH range (from 1to13), and can operate even with molecular chromophores for light-driven catalysis. [21] Different perspectives of cobalt-based Prussian blue analogues (PBAs) as WOCs have recently been explored by us and other researchers.…”

Tailored Assembly of Molecular Water Oxidation Catalysts on Photoelectrodes for Artificial Photosynthesis

“…(c, d) Effect of the deposition of CoFe‐PBAs on a photoanode on its performance for solar water oxidation: (c) on BiVO 4 and (d) on Fe 2 O 3 . Part (c) is reproduced with permission from ref . Copyright 2017 American Chemical Society, and part (d) is reproduced from ref …”

“…(e) Suggested energy level diagram explaining the different effects of CoFe‐PBAs on the PEC performance of BiVO 4 and on Fe 2 O 3 . Adapted with permission from ref . Copyright 2017 American Chemical Society.…”

“…Even for the same transition metal ions, their redox state can be varied by controlling the types and number of the inserted cations (Figure b) , . Compared to conventional molecular electrocatalysts, which can be deposited in a monolayer through complex chemical modification,, , they (1) can be readily deposited on various electrodes or photoelectrodes by bottom‐up assembly of precursors, (2) allow control over the deposited amount of catalytic active sites beyond a monolayer because of their porous structure and moderate electrical conductivity, and (3) have high stability in a wide pH range, from acidic to slightly basic pHs , , , , …”