A Functional Hydrogenase Mimic Chemisorbed onto Fluorine‐Doped Tin Oxide Electrodes: A Strategy towards Water Splitting Devices

Abstract

A diiron benzenedithiolate hydrogen‐evolving catalyst immobilized onto fluorine‐doped tin oxide (FTO) electrodes is prepared, characterized, and studied in the context of the development of water splitting devices based on molecular components. FTO was chosen as the preferred electrode material owing to its conductive properties and electrochemical stability. An FTO nanocrystalline layer is also used to greatly improve the surface area of commercially available FTO while preserving the properties of the material. Electrodes bearing a covalently anchored diiron catalyst are shown to be competent for electrocatalytic hydrogen evolution from acidic aqueous media at relatively low overpotential (500 mV) with a faradaic efficiency close to unity. Compared with bulk solution catalysts, the catalyst immobilized onto the electrode surface operates at roughly 160 mV lower overpotentials, yet with similar rates.

Unraveling Activity and Decomposition Pathways of [FeFe] Hydrogenase Mimics Covalently Bonded to Silicon Photoelectrodes

“…Analysis of the I 3d spectra showed the presence of Si-I bonds, also indicating incomplete surface coverage from the catalyst (Figure S9, Supporting Information). [31,44] The structure of the [FeFe] molecular catalyst changed during electrolysis, similar to a previously reported comparable diiron catalyst attached to fluorine doped tin oxide, [7] however, the detailed decomposition pathway was not expanded upon. It is notable that after 1 h electrolysis, the [FeFe] modified Si photoelectrochemical activity (Figure S10, Supporting Information) decreased in terms of onset and overpotential.…”

“…[8] However, only a handful of reports review the stability of semiconductor−molecule interfaces or their decomposition mechanisms. [7,[9][10][11] Herein, we tether organometallic catalysts onto semiconductor photoelectrodes to shed light on catalyst decomposition pathways during electrolysis. Moreover, the presence of functional molecules on the semiconductor surface can stabilize the interface by limiting growth of native oxides on unmodified surface sites.…”

“…However, investigation of the catalyst's integrity before and after electrolysis through surface analyzing techniques including X-ray photoelectron spectroscopy (XPS) revealed the absence of the active diiron hexacarbonyl center, with only a layer of 4-mercaptophenol remaining on the interface. Organometallic catalysts, especially [FeFe] hydrogenase mimics, have been widely applied in solar energy conversion [16][17][18][19][20][21][22][23] and are known to degrade, [7,17,[24][25][26] however, insights into their catalytic stability and decomposition mechanisms have received less attention. [9,27,28] This work presents an alternative surface sciencebased strategy to understand the decomposition pathways of molecular catalysts.…”

“…[3][4][5] Thus, there remains a need to develop an economically viable water splitting cell composed of a light-absorbing semiconductor for solarto-electron conversion coupled to a viable electrocatalyst for a rapid chemical conversion process.Currently, limitations of constructing an efficient semiconductor−catalyst interface include instability, insufficient light absorptivity of the semiconductor materials, and poor charge separation efficiency at the semiconductor−catalyst interface. [6,7] It is known that functionalizing semiconductor surfaces with organic compounds can tune surface properties by adjusting charge distribution, density of surface states, surface dipole, and electric fields at the semiconductor−molecule interface. [8] However, only a handful of reports review the stability of semiconductor−molecule interfaces or their decomposition mechanisms.…”

Iron(I)‐Based Carbonyl Complexes with Bridging Thiolate Ligands as Light‐Triggered CO Releasing Molecules (photoCORMs)

“…25 kcal · mol –1 for the interconversion between anti and both syn isomers . Syn‐exo isomeric forms of [{(OC) 3 Fe(μ‐SR)} 2 ] with R = aryl have only been observed in the crystalline state for the benzo‐1,2‐dithiolate and biphenyl‐2,2'‐dithiolate derivatives …”