Photocatalytic Water‐Splitting by Organic Conjugated Polymers: Opportunities and Challenges

Abstract

The future challenges associated with the shortage of fossil fuels and their current environmental impacts intrigued the researchers to look for alternative ways of generating green energy. Solar‐driven water splitting into oxygen and hydrogen is one of those advanced strategies. Researchers have studied various semiconductor materials to achieve potential results. However, it encountered multiple challenges such as high cost, low photostability and efficiency, and required multistep modifications. The conjugated polymers (CPs) have emerged as promising alternatives for conventional inorganic semiconductors. The CPs offer low cost, sufficient light absorption efficiency, excellent photo and chemical stability, and molecular optoelectronic tunable characteristics. Furthermore, organic CPs also present higher flexibility to tune the basic framework of the backbone of the polymers, amendments in the sidechain to incorporate desired functionalities, and much‐needed porosity to serve better for photocatalytic applications. This review article summarizes the recent advancements made in visible‐light‐driven water splitting covering the aspects of synthetic strategies and experimental parameters employed for water splitting reactions with special emphasis on conjugated polymers such as linear CPs, planarized CPs, graphitic carbon nitride (g‐C3N4), conjugated microporous polymers (CMPs), covalent organic frameworks (COFs), and conjugated polymer‐based nanocomposites (CPNCs). The current challenges and future prospects have also been described briefly.

Photoreforming of Waste Polymers for Sustainable Hydrogen Fuel and Chemicals Feedstock: Waste to Energy

“…Thus, we will focus on the design of substrate-specific photocatalysts. A mature form of PR, i.e., enhanced H 2 fuel production and selective synthesis of organic fine chemicals could be fully exploited with waste polymers through a targeted development of photocatalysts based on the chemical composition of the substrate or band gap structure, photocatalyst engineering. ,, As an example, metal oxide-based photocatalysts, (WO 3 , TiO 2 , ZnO) having valence band (VB) position much higher compared to the potential of the • OH/H 2 O redox couple (+2.27), can produce highly reactive • OH radicals, whereas metal chalcogenides (CdS, MoS 2 ) or carbon nitride (C 3 N 4 ) with inadequate VB position cannot perform this redox reaction . The separation of selective products would be the ultimate step of such a mature form of PR.…”

“…A mature form of PR, i.e., enhanced H 2 fuel production and ing. 319,339,340 As an example, metal oxide-based photocatalysts, (WO 3 , TiO 2 , ZnO) having valence band (VB) position much higher compared to the potential of the 341 The separation of selective products would be the ultimate step of such a mature form of PR. Selectivity in PR could also be achieved by controlling the energetics of the charge carriers, i.e., oxidation products such as hydroxyl radicals, hole states, and superoxides.…”

Recent Trends in Sustainable Solar Energy Conversion Technologies: Mechanisms, Prospects, and Challenges

“…89,90 The sluggish kinetics of the electron (e − ) and hole (h + ) pair separation or fast charge recombination and the propensity of semiconductors to undergo oxidative decomposition limit overall water splitting under aqueous conditions. 91,92 These issues can be improved by the proper design or engineering of photocatalysts used in the PEC-based water splitting approach. A conventional PEC cell consists of photoactive electrodes (anode or cathode) as a working electrode and the dark electrode as a counter electrode usually made of a Pt disk, an external bias, and a solar light irradiation source, as shown in panels c and d of Figure 1.…”

Recent advances in high-crystalline conjugated organic polymeric materials for photocatalytic CO2conversion

“…Other organic polymers including COFs, CTFs, and CMPs are synthesized by coupling two or more different monomers, generally by coupling reactions and condensation reactions. 43,44 Now, most COFs are synthesized in solvothermal systems under harsh conditions. However, most of them possess low crystallinity or are amorphous.…”