Functional Integration of Catalysts with Si Nanowire Photocathodes for Efficient Utilization of Photogenerated Charge Carriers

Abstract

Low-cost catalysts with high activity and durability are necessary to achieve efficient large-scale energy conversion in photoelectrochemical cell (PEC) systems. An additional factor that governs the construction of photoelectrodes for PECs is the spatial control of the catalysts for efficient utilization of photogenerated charge carriers. Here, we demonstrate spatial decoupling of the light-absorbing and catalytic components in hierarchically structured Si-based photocathodes for the hydrogen evolution reaction (HER). By simply modifying a well-known metal-assisted chemical etching procedure, we fabricated a Si nanowire (NW) array-based photocathode with Ag–Pt catalysts at the base and small amounts of the Pt catalyst at the NW tips. This approach simultaneously mitigates the parasitic light absorption by the catalytic layers and recombination of charge carriers owing to the long transport distance, resulting in improved photoelectrochemical HER performance under simulated AM 1.5G illumination.

Heterojunctions Comprised of Graphitic Carbon Nitride Nanosheets and SnO2 Nanoparticles with Exposed {221} Crystal Facets for Photocatalytic Hydrogen Evolution

“…Therefore, it is particularly paramount to explore a photocatalyst that has high photocatalytic activity under visible light and is environmentally friendly. − Graphitic carbon nitride (g-C 3 N 4 ), a metal-free organic polymer with a π–π-conjugated structure, has an adjustable band structure and reliable chemical stability. − Besides, the energy band structure accords with the requirements of photocatalytic water splitting for H 2 production; that is, the conduction band (CB) potential is more negative than that of H + /H 2 (0 eV vs NHE) . Despite the above two advantages, g-C 3 N 4 has a narrow visible-light response, high recombination rate of charge carriers, , and relatively low catalytic activity. Due to these shortcomings, the photocatalytic efficiency is very poor .…”

“…15−17 Besides, the energy band structure accords with the requirements of photocatalytic water splitting for H 2 production; that is, the conduction band (CB) potential is more negative than that of H + /H 2 (0 eV vs NHE). 18 Despite the above two advantages, g-C 3 N 4 has a narrow visible-light response, high recombination rate of charge carriers, 19,20 and relatively low catalytic activity. Due to these shortcomings, the photocatalytic efficiency is very poor.…”

NiCo2S4 cocatalyst supported Si nanowire heterostructure for improved solar-driven water reduction: experimental and theoretical insights

“…[12][13][14] However, ineffective charge-transfer kinetics at Si/electrolyte, and limited hydrogen evolution reaction (HER) active sites remain difficult and challenging to fabricate highly efficient p-Si photocathodes. 6,[10][11][12][13][14][15][16] Therefore, researchers are devoting more time and effort to the design and development of efficient lowdimension nanostructures of Si as photocathodes using various surface modication strategies. [16][17][18][19] Among them, the formation of photoelectrode heterostructures with various non-precious HER co-catalysts is an effective tool for attaining the desired properties for the solar-driven water splitting process.…”

Photo-assisted decoration of Ag-Pt nanoparticles on Si photocathodes for reducing overpotential toward enhanced photoelectrochemical water splitting

“…They observed that the Si photocathode with an ultralow loading of Pt catalyst exhibited a comparable PEC performance relative to the counterpart with a thick Pt layer. Although Pt is considered the most active element in HER and the bulk Pt has excellent stability, the long-term stability of Pt NPs is much worse than that of the bulk Pt in acidic environments [24][25][26][27]. To obtain Pt-based catalysts with long-term stability, high catalytic efficiency, and low consumption, the catalysts of Pt-based alloys have received increased attention.…”