Nanowire Array Structures for Photocatalytic Energy Conversion and Utilization: A Review of Design Concepts, Assembly and Integration, and Function Enabling

Abstract

Environmental pollution and the shortage of clean and renewable energy resources are two of the grand challenges the world is facing today. [1] Photocatalysis is one active research area toward the effort of conversion and utilization of sunlight energy to solve these challenges with annual publication of more than 2000 peer-reviewed papers. [2] Photocatalysis finds its potential applications in the direct conversion of sunlight energy into electricity and fuels (hydrogen, hydrocarbons) using photoelectrochemical (PEC) solar cells (dye-sensitized/ quantum-dot-sensitized solar cells) [3][4][5] and photocatalytic waterThe increasing human demand for clean and renewable energy and a cleaner environment has stimulated various materials related research and development for efficient solar energy conversion and utilization, photocatalytic environmental remediation, and photoassisted selective conversion of organic compounds. Among the various candidate solutions to improving the efficiency of these processes, semiconductor nanowire (NW) and nanorod (NR) array structures have been offering a unique tool box combining desirable characteristics in structure, function, and applicability. Efficient photocatalytic energy conversion requires excellent light absorption, readily charge separation, transport, and collection, as well as fast kinetics of interfacial reactions and mass transport of reactants. The long axis of the NW enables adequate light absorption, while the radical axis provides short electron-hole separation distance. Additionally, the NW arrays have relatively high surface area to facilitate interfacial kinetics while their open pore structure allows good mass transport properties. This study reviews the current status of research on NW and NR array structures of some most popular semiconducting materials for photocatalytic energy conversion and utilization including photocatalytic water splitting and CO 2 reduction/fixation, dye/quantum dot sensitized solar cells, and other photoassisted reactive applications such as pollutant degradation, selective conversion of organic compounds, and biological disinfection.

Steering Photoelectrons Excited in Carbon Dots into Platinum Cluster Catalyst for Solar‐Driven Hydrogen Production

“…[3][4][5][6] Photocatalytic H 2 evolution reaction (HER) proceeds a consistent route that protons in solution are reduced by photoexcited electrons to hydrogen atoms chemisorbed on catalyst surface followed by their desorption into hydrogen gas. [7,8] Thus, the injection of thermodynamic photoelectrons and the Gibbs free energy of atomic H adsorption (ΔG H ) are two critical factors in determining the photocatalytic HER activities of catalysts. [9] Platinum (Pt) yields the most desirable ΔG H of near-zero value (−0.09 eV), [10,11] while its photochemical inertness toward sunlight restricts the potential for direct photocatalysis.…”

Metal–Organic Framework Derived Co3O4/TiO2/Si Heterostructured Nanorod Array Photoanodes for Efficient Photoelectrochemical Water Oxidation

“…photoexcitation of semiconductor photoanode; the separation and migration of photoinduced carriers; the surface water reduction on the cathode; and water oxidation on the photoanode with photoinduced electrons/holes. [20][21][22] For instance, via constructing semiconductor heterojunction with matched band position, the separation and transportation of photoinduced carrier can be effectively enhanced (such as Bi 2 MoO 6 /Si, [23] Ag/Fe 2 O 3 , [24] NiFe-LDH/C 3 N 4[25] heterojunction). [12,13] Metal oxides (MOs), such as TiO 2 , [14] α-Fe 2 O 3 , [15] and WO 3 , [16,17] have been widely investigated as the photoanode materials for PEC water splitting, for their low-cost, environmentfriendly properties.…”

“…[12,13] Metal oxides (MOs), such as TiO 2 , [14] α-Fe 2 O 3 , [15] and WO 3 , [16,17] have been widely investigated as the photoanode materials for PEC water splitting, for their low-cost, environmentfriendly properties. [20][21][22] For instance, via constructing semiconductor heterojunction with matched band position, the separation and transportation of photoinduced carrier can be effectively enhanced (such as Bi 2 MoO 6 /Si, [23] Ag/Fe 2 O 3 , [24] NiFe-LDH/C 3 N 4 [25] heterojunction). [18,19] Therefore, designing composited photoanodes with proper band-gap energy structure is considered to be a promising route to overcome these limitations induced poor PEC performance.…”

“…[18,19] Therefore, designing composited photoanodes with proper band-gap energy structure is considered to be a promising route to overcome these limitations induced poor PEC performance. [20][21][22] For instance, via constructing semiconductor heterojunction with matched band position, the separation and transportation of photoinduced carrier can be effectively enhanced (such as Bi 2 MoO 6 /Si, [23] Ag/Fe 2 O 3 , [24] NiFe-LDH/C 3 N 4 [25] heterojunction). Particularly, benefiting from the outstanding visiblelight response performance and carrier mobility within silicon, it has long been regarded as the most suitable material to build the solar energy conversion device.…”

Recycling and Elimination of Wastes obtained from Agriculture by using Nanotechnology: Nanosensors

“…As the above mechanism, one of the main uses of photocatalysts is generate ROS known, also named as highly reactive oxygen species, which already mentioned that generally present as hydroxyl radicals explained (can perform degradation of organic pollutants). Photocatalysts can provide an efficient, cost effective and promising technology not only for the degradation of organic compounds, but for possible biological disinfection, including applications in the wastewater treatment [40].…”