Graphitic carbon nitride nano-emitters on silicon: a photoelectrochemical heterojunction composed of earth-abundant materials for enhanced evolution of hydrogen

Abstract

Graphitic carbon nitride is a promising heterogeneous catalyst for light-induced generation of hydrogen. Here, we report the successful formation of nano-scaled carbon nitride structures on silicon, mitigating the known limitations of charge transport within bulky C-N networks. An efficient photoelectrochemical heterojunction is thereby realized, developed from earth-abundant materials only.The conversion of solar energy to chemical energy is one of the principal routes to establish a green global economy.1 Particularly, hydrogen as a product of solar water splitting may assume a decisive role upon transition from fossil to renewable energy resources.2 For realization of the solar-to-hydrogen conversion process by photoelectrochemical water splitting, suitable photoelectrodes still have to be developed and to meet important demands such as efficiency and durability. Most critical, electrode fabrication has to rely on cost-saving material consumption, and the use of earth-abundant materials appears inevitable for novel device architectures. In this respect, the combination of silicon and polymeric graphitic carbon nitride (g-C 3 N 4 ) represents a highly attractive heterostructure, integrating a state-of-the-art photoabsorber and a promising photocatalyst. Silicon-based photoelectrodes on the one hand, already reached near-record efficiencies in light-induced evolution of hydrogen but had to be activated by noble-metal catalysts.3,4 On the other hand, g-C 3 N 4 is an established candidate for photocatalytic hydrogen production since the report of Wang et al. in 2008 (ref. 5) which boosted almost instantaneously the interest in this material due to the prospect of solar fuel generation without use of noble metal catalysts. 6-10

Efficient and Stable TiO2:Pt–Cu(In,Ga)Se2 Composite Photoelectrodes for Visible Light Driven Hydrogen Evolution

“…Very recently, this is also observed for a silicon-based heterocontact (7 of 9) 1402148 wileyonlinelibrary.com photocathode device consisting of ultrathin polymeric carbon nitride nanosheets on prestructured p-type silicon. [ 31 ] Here, we found also an anodic onset potential shift of ≈0.3 V of the solar hydrogen evolution as a consequence of an internal built-in voltage.…”

Complementing Graphenes: 1D Interplanar Charge Transport in Polymeric Graphitic Carbon Nitrides

“…Transmission electron microscopy images for SG-CN are reported by Kailasam et al [ 2 ] Scanning electron microscopy images of photoelectrodes utilitzing PCN can be found in refs. [ 7,46,47 ] .…”

“…[ 13,17,20 ] Thus, while a well-founded transport model is still missing, Merschjann et al suggested a predominance of interplanar transport, [ 14 ] depicted in Figure 1 , together with Polymeric graphitic carbon nitrides (CN) have recently attracted considerable interest as crystalline all-organic wide-bandgap semiconductors. They have been used in a wide range of photocatalytic applications, especially for solar water-splitting, [1][2][3][4][5][6][7] as well as in photovoltaics, as tunable yellow phosphors and fl uorescent markers for bioimaging. [8][9][10][11][12] Despite the large variety of reported synthesis routes and substantial progress in characterization of the materials, the nature of charge transport in CN has not been unveiled to date.…”

Binary Multifunctional Ultrabroadband Self‐Powered g‐C3N4/Si Heterojunction High‐Performance Photodetector

“…Lublow et al reported two‐step hydrofluoric (HF) acid etching method first to modify the silicon surface, second to under etch the g‐C 3 N 4 deposited on the Si substrate leading to nanosheets or lamellae embedded into the Si substrate for photocatalytic applications. The fabricated hybrid structure displayed rectifying heterojunction behavior, enhancing the photogenerated electron conduction toward the g‐C 3 N 4 /Si interface …”