Electrochemical Engineering of Nanoporous Materials for Photocatalysis: Fundamentals, Advances, and Perspectives

Abstract

Photocatalysis comprises a variety of light-driven processes in which solar energy is converted into green chemical energy to drive reactions such as water splitting for hydrogen energy generation, degradation of environmental pollutants, CO2 reduction and NH3 production. Electrochemically engineered nanoporous materials are attractive photocatalyst platforms for a plethora of applications due to their large effective surface area, highly controllable and tuneable light-harvesting capabilities, efficient charge carrier separation and enhanced diffusion of reactive species. Such tailor-made nanoporous substrates with rational chemical and structural designs provide new exciting opportunities to develop advanced optical semiconductor structures capable of performing precise and versatile control over light–matter interactions to harness electromagnetic waves with unprecedented high efficiency and selectivity for photocatalysis. This review introduces fundamental developments and recent advances of electrochemically engineered nanoporous materials and their application as platforms for photocatalysis, with a final prospective outlook about this dynamic field.

Harnessing Slow Light in Optoelectronically Engineered Nanoporous Photonic Crystals for Visible Light-Enhanced Photocatalysis

“…As such, significant efforts have been devoted on developing advanced materials for effective electron–hole separation and increasing surface reduction–oxidation reaction sites for visible light-driven photocatalysis via approaches such as substitutional doping, , deposition of co-catalysts, , and nanostructural engineering of semiconductors. , Of all these, engineering nanostructural engineering of semiconductor materials in porous photonic crystals (PCs) enables new ways of harnessing interactions between atoms and incident electromagnetic waves for photocatalysis. These platform materials provide (i) dynamic paths to enhance the transfer of photopromoted electrons and holes, (ii) a high number of functional redox centers with a high specific surface area, and (iii) a nanoporous architecture that provides enhanced flow of reduction–oxidation species . Rational design of nanoporous semiconductor PCs also enables enhanced photon–semiconductor interactions through optical phenomena such as multiple scattering, Bragg diffraction, slow light, light recirculation, and surface plasmons. − …”

“…These platform materials provide (i) dynamic paths to enhance the transfer of photopromoted electrons and holes, (ii) a high number of functional redox centers with a high specific surface area, and (iii) a nanoporous architecture that provides enhanced flow of reduction−oxidation species. 15 Rational design of nanoporous semiconductor PCs also enables enhanced photon−semiconductor interactions through optical phenomena such as multiple scattering, Bragg diffraction, slow light, light recirculation, and surface plasmons. 16−18 Zheng et al demonstrated that titanium dioxide (TiO 2 ) inverted opal PCs featuring a photonic stop band (PSB) at 660 nm outperform benchmark P25 TiO 2 nanoparticles by ∼52% in breaking down methylene blue (MB)a model organic with the maximum optical absorption at 664 nmunder visible light irradiation.…”

Recent Advances in Opal/Inverted Opal Photonic Crystal Photocatalysts

“…In addition, to fill the targeted precursor into template voids, various methods have been adopted, including chemical vapor deposition (CVD), atomic layer deposition (ALD), electrochemical deposition (ECD), and sol–gel method. [ 101 ]…”

Engineering of Broadband Nanoporous Semiconductor Photonic Crystals for Visible-Light-Driven Photocatalysis

“…Semiconductor thin films are inefficient for photocatalysis since electronic band bending only allows one type of charge carrier, either e – or h + , to be available for reaction . In contrast, illumination of nanostructured semiconductors in the form of nanoparticulate aggregate films, nanopillars, inverted opals, , and nanoporous films stimulates the generation of excitons on the semiconductor’s surface. This then enables both reductive and oxidative pathways.…”