Photoelectrocatalysis: principles, nanoemitter applications and routes to bio-inspired systems

Abstract

An overview on processes that are relevant in light-induced fuel generation, such as water photoelectrolysis or carbon dioxide reduction, is given. Considered processes encompass the photophysics of light absorption, excitation energy transfer to catalytically active sites and interfacial reactions at the catalyst/solution phase boundary. The two major routes envisaged for realization of photoelectrocatalytic systems, e.g. bio-inspired single photon catalysis and multiple photon inorganic or hybrid tandem cells, are outlined. For development of efficient tandem cell structures that are based on non-oxidic semiconductors, stabilization strategies are presented. Physical surface passivation is described using the recently introduced nanoemitter concept which is also applicable in photovoltaic (solid state or electrochemical) solar cells and first results with p-Si and p-InP thin films are presented. Solar-to-hydrogen efficiencies reach 12.1% for homoepitaxial InP thin films covered with Rh nanoislands. In the pursuit to develop biologically inspired systems, enzyme adsorption onto electrochemically nanostructured silicon surfaces is presented and tapping mode atomic force microscopy images of heterodimeric enzymes are shown. An outlook towards future envisaged systems is given.

Semiconductor Surface Transformations for Photoelectrochemical Energy Conversion

“…For p-type absorbers, conduction band alignment is not uncommon. 31 Indium oxides, for example, have electron affinities around 4.5eV, hence efficient excess minority transfer from most semiconductor conduction bands becomes possible. An example has been drawn in Fig.…”

“…The structure Rh/ interphase/p-InP (100):(2×4)/InP substrate was immersed into 1M HClO 4 and cycled for further optimization which resulted in a solarto-hydrogen efficiency of 14.5% if the efficiency determination from Ref. 47 is used 31 and of η = 12.4% if one takes the potential of the hydrogen redox couple as reference. The output characteristics are displayed in Fig.…”

Perspectives and Advances in Photocatalysis

“…The individual steps of this sequence comprise of absorption by the semiconductor photocatalyst, composite materials or dyes. The excitation energy transfer from the absorber to the catalyst is usually assumed to be an electronic conduction process, which, in less ordered semiconducting materials could also be due to a hopping mechanism and dispersive transport of the light-induced excess electrons in the conduction band of semiconductor to its surface (Lewerenz et al 2010). These photoprocesses together with electric energy produce synergistic effect in the degradation of chemical compounds.…”

Fundamental Aspects of Electrodeposition for the Realization of Plasmonic Nanostructures

“…In recent work, high photocurrents were obtained on a Rh nanoparticle/oxide/InP structure for light-induced hydrogen evolution. [9] We presently investigate whether the surface plasmon resonance of Rh nanoparticles of about 3-5 nm radius and their spatial arrangement influences the absorption/reflectivity of the device. In principle, both, the resonant collective electron density variation of the surface mode and the enhanced electric field strength close to the interface to a dielectric such as water can influence the actual catalytic process and the optical behaviour.…”