Nickel‐Based Dye‐Sensitized Photocathode: Towards Proton Reduction Using a Molecular Nickel Catalyst and an Organic Dye

Abstract

To construct an efficient dye‐sensitized photo‐electrochemical tandem cell for hydrogen production, it is crucial to understand the working principles of both the photoanode and the photocathode. Herein, the anchoring of a proton‐reduction catalyst and an organic dye molecule on metal oxides is studied for the preparation of a photocathode. On TiO2, the Ni catalyst behaves as a good electrocatalyst (−250 μA cm−2) in acidic water (pH 2). The Ni catalyst and the organic dye were co‐immobilized on NiO to form a solely Ni‐based photocathode. The electron‐transfer steps were investigated by using various techniques (IR, UV/Vis, and fluorescence spectroscopy, and (photo)electrochemistry). Despite the observed successful single‐electron‐transfer steps between all of the components, photocatalysis did not yield any hydrogen gas. Possible bottlenecks that prevent photocatalytic proton reduction are poor electron transfer because of aggregation, charge recombination from the catalyst to the NiO, or instability of the catalyst after the first reduction.

Electro- and Solar-Driven Fuel Synthesis with First Row Transition Metal Complexes

“…A [Ni(P 2 N 2 ) 2 ] 2+ catalyst modified with hydroxamic acid groups was coimmobilized on a NiO electrode alongside a naphthalene diimide organic dye, but this system did not evolve H 2 . 968 The lack of PEC activity was attributed to dye aggregation, which would cause fast recombination between the reduced dye and holes in NiO, limiting successful charge transfer to the HEC. Examples for H 2 evolution with anchored [Ni(P 2 N 2 ) 2 ] 2+ catalysts through supramolecular assemblies (Figure 54b) are summarized in section 6.3.2.…”

Using Surface Amide Couplings to Assemble Photocathodes for Solar Fuel Production Applications

“…To increase photocathode performance, many photocathode designs have focused on changing the electrode assembly. Methods for assembly include using layer-by-layer strategies, 36,37,[39][40][41][42] adding hydrophobic layers, 43 codeposition methods, 7,23,[44][45][46] covalently linking the dye and catalyst, [47][48][49][50][51] using electron shuttling layers, 52 using supramolecular strategies, 53 changing the semiconductor material, 54 and using atomic layer deposition. 55 While these are all very important studies, the stability of the anchoring group in photocathode architectures has received rather little attention.…”

“…To the best of our knowledge, only one study has focused on changing the molecules' anchoring group to improve performance. 44 This is surprising, because it is a common strategy in photoanode assembly methods. 3,16,[56][57][58][59][60][61] In photocathodes, stability can be a major issueif the molecular components do not remain bound on the electrode, then the photocathodes will not function efficiently.…”

Using high-throughput virtual screening to explore the optoelectronic property space of organic dyes; finding diketopyrrolopyrrole dyes for dye-sensitized water splitting and solar cells

“…Similarly, the chemically related indigo molecule absorbs green to red light, reflecting back only blue light, and is the dye that colours jeans blue. 3 However, the use of organic dyes and pigments is not limited to simply providing colour, they also find application in dye-sensitized solar-cells (DSSCs) [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] dyesensitized photocatalysts [21][22][23][24][25][26] and in organic electronics, for example in organic field-effect transistors (OFETs), 2,27,28 organic photovoltaics (OPV) 29 and materials for singlet fission. [30][31][32][33] In DSSCs, the ability of a dye to absorb light of a particular range of wavelengths and inject photoexcited electrons or holes into a semiconductor that would otherwise be transparent to that light, ultimately leads to the generation of an electrical current.…”