Hydrogen generation from photoelectrochemical water splitting based on nanomaterials

Abstract

Hydrogen is potentially one of the most attractive and environmentally friendly fuels for energy applications. Safe and efficient generation, storage, and utilization of hydrogen present major challenges in its widespread use. Hydrogen generation from water splitting represents a holy grail in energy science and technology, as water is the most abundant hydrogen source on the Earth. Among different methods, hydrogen generation from photoelectrochemical (PEC) water splitting using semiconductors as photoelectrodes is one of the most scalable and cost-effective approaches. Compared to bulk materials, nanostructured semiconductors offer potential advantages in PEC application due to their large surface area and size-dependent properties, such as increased absorption coefficient, increased band-gap energy, and reduced carrier-scattering rate. This article provides a brief overview of some recent research activities in the area of hydrogen generation from PEC water splitting based on nanostructured semiconductor materials, with a particular emphasis on metal oxides. Both scientific and technical issues are critically analyzed and reviewed.SEM image of ZnO nanowire array on ITO substrate (left) and linear sweep voltammograms from undoped ZnO nanowires in the dark, undoped ZnO nanowires and N-doped ZnO nanowires at 100 mW/cm 2 .

Hydrogen Production by Photoreforming of Renewable Substrates

“…In addition, the band gap energy may be in principle tuned with particle size, in order to increase light absorption in the solar spectrum [61]. However, size effects sometimes induce an upward/downward shift of the CB/VB edges, complicating the prediction of the exact band positions [62].…”

Electrodeposition of Ni oxide on TiO2 nanotube arrays for enhancing visible light photoelectrochemical water splitting

“…The electrolyte solution consisted of 0.5 wt% ammonium fluoride (NH 4 3 . Deposition experiments were performed in a three-electrode system (the TiO 2 /Ti as a working electrode, nickel plate as a counter electrode and a saturated calomel electrode as a reference electrode) desecrated with N 2 .…”

“…Since the discovery of photoelectrochemical water splitting using n-type TiO 2 for photoanodes, hydrogen generation by water photoelectrolysis has been a topic of great interest [1][2][3]. Among the semiconductor materials, titanium dioxide (TiO 2 ) has been considered one of the most promising photocatalytic materials due to its unique properties including relatively low cost, non-toxicity, chemical stability, and high photo stability [4][5][6][7].…”

Polymorphism and Structural Distortions of Mixed-Metal Oxide Photocatalysts Constructed with α-U3O8 Types of Layers

“…Photocatalysis for water splitting can be divided into four mechanistic steps: (a) absorption of photons to excite electrons from the valence band to the conduction band; (b) charge separation electrons and holes; (c) diffusion of the photoexcited electrons and holes to the surfaces as driven by the space-charge layer, and (d) surface chemical reactions between the charge carriers and the adsorbates [85][86][87][88][89]. The illustration in Figure 9 shows a photocatalyst particulate and the four basic steps, where (d) also includes the competing volume and surface recombination processes.…”