Materials and Mechanisms of Photo‐Assisted Chemical Reactions under Light and Dark Conditions: Can Day–Night Photocatalysis Be Achieved?

Abstract

The photoassisted catalytic reaction, conventionally known as photocatalysis, is expanding into the field of energy and environmental applications. It is widely known that the discovery of TiO2‐assisted photochemical reactions has led to several unique applications, such as degradation of pollutants in water and air, hydrogen production through water splitting, fuel conversion, cancer treatment, antibacterial activity, self‐cleaning glasses, and concrete. These multifaceted applications of this phenomenon can be enriched and expanded further if this process is equipped with more tools and functions. The term “photoassisted” catalytic reactions clearly emphasizes that photons are required to activate the catalyst; this can be transcended even into the dark if electrons are stored in the material for the later use to continue the catalytic reactions in the absence of light. This can be achieved by equipping the photocatalyst with an electron‐storage material to overcome current limitations in photoassisted catalytic reactions. In this context, this article sheds lights on the materials and mechanisms of photocatalytic reactions under light and dark conditions. The manifestation of such systems could be an unparalleled technology in the near future that could influence all spheres of the catalytic sciences.

Insights into the TiO2-Based Photocatalytic Systems and Their Mechanisms

“…Similarly, the photo-induced electrons can be forced to migrate into the bulk from surface, where they can be delocalized in possible Ti sites. Furthermore, it is also predicted that in TiO 2 it is of more possible for bulk trapping rather than surface trapping and thereby TiO 2 shows relatively enhanced photocatalytic activities as compared to the other semiconducting oxide-based photocatalysts [38][39][40].…”

Concerted catalytic and photocatalytic degradation of organic pollutants over CuS/g-C3N4 catalysts under light and dark conditions

“…Among these methods, photocatalytic degradation has emerged as one of the most promising technologies because it is typically inexpensive and environmentally friendly, readily uses solar light, and does not generate secondary pollutants [8], [9], [10]. However, common photocatalysts, such as TiO 2 , ZnO, Fe 2 O 3 , SrTiO 3 , or other oxide-based species, show low or no catalytic activity in the absence of light, which greatly hinders their practical applicability for the continuous, around-the-clock degradation of organic pollutants [8], [9], [10], [11], [12], [13]. Therefore, developing novel photocatalysts that are highly efficient in the absence of light is a high priority, and would have great significance for achieving continuous catalytic degradation of organic pollutants.…”

Light-driven charge accumulation of a molecular Cu(I) complex for storage of photoredox equivalents

“…9, 07745 Jena, Germany. 3 Centre for Energy and Environmental Chemistry (CEEC), Friedrich Schiller University Jena, Philosophenweg 7a, 07743 Jena, Germany. 4 School of chemical Sciences, Dublin City University, Dublin, Ireland.…”

“…Dietzek 1,2,3 The diurnal day/night cycle is presently of great interest for harvesting solar energy aimed at rendering suitable energy storage schemes. To this end we present a noblemetal free system based on a Cu(I) 4H-imidazolate complex, that is efficiently photoreduced in the presence of a sacrificial donor.…”

“…Besides photoelectrochemical schemes 2 , several solid state material based approaches have been proposed to harvest light in form of excited electrons and to store these photoredox equivalents with subsequent consumption in the dark. Most examples for photoelectron storage are metal oxides 3 , such as TiO 2 -WO 3 , TiO 2 -Cu 2 O or La 2 NiO 4 as well as carbon nitrites 3,4 . Furthermore, molecular ruthenium complexes were developed for accumulation of photoredox equivalents [5][6][7][8][9] but not investigated towards lightdriven charging and dark consumption.…”