CO₂ reduction with Re(i)–NHC compounds: driving selective catalysis with a silicon nanowire photoelectrode

Abstract

The CO-reduction activity of two Re(i)-NHC complexes is investigated employing a silicon nanowire photoelectrode to drive catalysis. Photovoltages greater than 440 mV are observed along with excellent selectivity towards CO over H formation. The observed selectivity towards CO production correlates with strong adsorption of the catalysts on the photoelectrode surface.

Hybrid Photocathodes for Carbon Dioxide Reduction: Interfaces for Charge Separation and Selective Catalysis

“…[57] For example, in a recent study of ReÀ Nheterocyclic carbene complexes (16 and 17) with a p-Si photocathode, addition of 5 % water to an acetonitrile electrolyte was found to be sufficient to prevent one of the two catalysts studied adsorbing onto the photocathode. [86] Finally, (4) under conditions where the photoelectron flux is relatively low, it is also feasible that diffusion of partially reduced species away from the electrode surface may occur prior to completion of the catalytic cycle.…”

“…The approach of using the catalyst in solution does have several disadvantages: (1) the high concentration of catalyst in solution can cause parasitic light absorption, (2) large portions of the catalyst are not in contact with the semiconductor surface at any one‐time decreasing the probability of charge transfer, [83,84] (3) the nature/orientation of the catalyst‐electrode interaction is hard to control and highly dependent on the electrolyte, [54] light intensity and the applied potential [70,85] and some molecular catalysts maybe be decomposed during long illumination periods [57] . For example, in a recent study of Re−N‐heterocyclic carbene complexes ( 16 and 17 ) with a p ‐Si photocathode, addition of 5 % water to an acetonitrile electrolyte was found to be sufficient to prevent one of the two catalysts studied adsorbing onto the photocathode [86] . Finally, (4) under conditions where the photoelectron flux is relatively low, it is also feasible that diffusion of partially reduced species away from the electrode surface may occur prior to completion of the catalytic cycle.…”

Properties and prospects for rhenium(i) tricarbonyl N-heterocyclic carbene complexes

“…The use of catalysts can increase this rate and promote multi-electron reduction while at the same time afford some product selectivity. Re(I) complexes of the type Re(CO) 3 (bpy)Cl have long been known to act as effective catalysts in the electro-and photocatalytic reduction of CO 2 , 39 but only very recently have isoelectronic Re(CO) 3 (NHC)X complexes, where NHC is a bidentate carbene ligand that binds the metal through the carbenic carbon and an imine type N-donor, been explored in this context. Advantageously, more facile modification of the steric and electronic parameters of the NHC ligand compared to the bipyridine-based system can lead to more selective and efficient catalysts in the former case.…”

Efficient photoelectrocatalytic CO2 reduction by cobalt complexes at silicon electrode

“…Integrating molecular elecrocatalysts with semiconductor photoabsorbers is an attractive approach to obtain efficient photoelectrochemical (PEC) systems for CO2 conversion. Over the past three decades, molecular electrocatalysts based on precious metals have been commonly investigated because of their high selectivity and efficiency [3][4][5][6][7][8][9][10][11]. Only a few earth-abundant metal-based molecular electrocatalysts, such as iron, cobalt (Co), nickel, and manganese (Mn) complexes, have been investigated [12][13][14][15][16][17][18][19].…”

“…Only a few earth-abundant metal-based molecular electrocatalysts, such as iron, cobalt (Co), nickel, and manganese (Mn) complexes, have been investigated [12][13][14][15][16][17][18][19]. Semiconductor materials based on metal oxides, chalcogenides, and silicon (Si) are able to efficiently separate photogenerated charges, thus enhancing photoelectric conversion efficiency and reaction kinetics [3,7,11,16,17,20]. Incorporation of noble metal electrocatalysts into semiconductor PEC systems has been mostly investigated for homogeneous and heterogeneous CO2 catalytic reduction systems [3,5,7,11].…”