A Robust, Precious‐Metal‐Free Dye‐Sensitized Photoanode for Water Oxidation: A Nanosecond‐Long Excited‐State Lifetime through a Prussian Blue Analogue

Abstract

Herein, we establish a simple synthetic strategy affording a heterogeneous, precious metal‐free, dye‐sensitized photoelectrode for water oxidation, which incorporates a Prussian blue (PB) structure for the sensitization of TiO2 and water oxidation catalysis. Our approach involves the use of a Fe(CN)5 bridging group not only as a cyanide precursor for the formation of a PB‐type structure but also as an electron shuttle between an organic chromophore and the catalytic center. The resulting hetero‐functional PB‐modified TiO2 electrode demonstrates a low‐cost and easy‐to‐construct photoanode, which exhibits favorable electron transfers with a remarkable excited state lifetime on the order of nanoseconds and an extended light absorption capacity of up to 500 nm. Our approach paves the way for a new family of precious metal‐free robust dye‐sensitized photoelectrodes for water oxidation, in which a variety of common organic chromophores can be employed in conjunction with CoFe PB structures.

Precious Metal‐Free Photocatalytic Water Oxidation by a Layered Double Hydroxide‐Prussian Blue Analogue Hybrid Assembly

“…A comparison of XPS profiles before and after mixing indicates that the binding energies of Zn 2p and Cr 2p exhibit slightly positive shifts after mixing [20] . Cobalt retains its +2 and +3 oxidation states, [35,43,44] whereas the amount of Fe 2+ ions in the mixed‐valent iron sites increases upon mixing suggesting an electron transfer from LDH to PBA structures (Figures 3 and S8), [27] which is in agreement with FTIR profile of LDH‐PB‐1 sample.…”

“…Since they exhibit poor photocurrent efficiencies, the general strategy is to couple CoFe‐PBAs with suitable photosensitizers and semiconductors to utilize them for the light‐driven water oxidation process [27,32] . Herein, we prepare SC‐WOC hybrid assembly by coupling a CoFe‐PBA with a ZnCr‐LDH since i) they are precious metal free, ii) they can be prepared by straightforward solution chemistry, and iii) CoFe‐PBAs are projected to have a suitable band energy alignment that can facilitate charge transfer from the valence band of ZnCr‐LDH for the water oxidation reaction [33–36] …”

“…[27,32] Herein, we prepare SC-WOC hybrid assembly by coupling a CoFe-PBA with a ZnCr-LDH since i) they are precious metal free, ii) they can be prepared by straightforward solution chemistry, and iii) CoFe-PBAs are projected to have a suitable band energy alignment that can facilitate charge transfer from the valence band of ZnCr-LDH for the water oxidation reaction. [33][34][35][36]…”

Strong Light–Matter Interactions in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting

“…To expedite the electron dynamics in the photoanode/electrolyte interface, a WOC could be employed. Recently, many groups have explored the integration of a Prussian blue assembly with semiconductor and molecular chromophores . Overall, it was demonstrated that the addition of CoFe‐PBA as a WOC can significantly improve the carrier dynamics of the electrode, by mediating the water oxidation reaction.…”

“…In recent studies, we developed a facial route based on oblique angle deposition to synthesize plasmonic nanostructures on a large scale. Moreover, we demonstrated that as a result of the cyanide chemistry, so‐called CoFe‐Prussian blue analog (PBA) is a strong and robust water oxidation catalyst (WOC), when connected to an organic chromophore . Inspired by these studies, herein, we adopt an extendable platform for the realization of a catalyst‐plasmonic architecture to improve the performance of semiconductor photoanodes with a facial and large‐scale compatible design in PEC‐WS.…”