Red Phosphorus: An Up-and-Coming Photocatalyst on the Horizon for Sustainable Energy Development and Environmental Remediation

Abstract

Photocatalysis is a perennial solution that promises to resolve deep-rooted challenges related to environmental pollution and energy deficit through harvesting the inexhaustible and renewable solar energy. To date, a cornucopia of photocatalytic materials has been investigated with the research wave presently steered by the development of novel, affordable, and effective metal-free semiconductors with fascinating physicochemical and semiconducting characteristics. Coincidentally, the recently emerged red phosphorus (RP) semiconductor finds itself fitting perfectly into this category ascribed to its earth abundant, low-cost, and metal-free nature. More notably, the renowned red allotrope of the phosphorus family is spectacularly bestowed with strengthened optical absorption features, propitious electronic band configuration, and ease of functionalization and modification as well as high stability. Comprehensively detailing RP’s roles and implications in photocatalysis, this review article will first include information on different RP allotropes and their chemical structures, followed by the meticulous scrutiny of their physicochemical and semiconducting properties such as electronic band structure, optical absorption features, and charge carrier dynamics. Besides that, state-of-the-art synthesis strategies for developing various RP allotropes and RP-based photocatalytic systems will also be outlined. In addition, modification or functionalization of RP with other semiconductors for promoting effective photocatalytic applications will be discussed to assess its versatility and feasibility as a high-performing photocatalytic system. Lastly, the challenges facing RP photocatalysts and future research directions will be included to propel the feasible development of RP-based systems with considerably augmented photocatalytic efficiency. This review article aspires to facilitate the rational development of multifunctional RP-based photocatalytic systems by widening the cognizance of rational engineering as well as to fine-tune the electronic, optical, and charge carrier properties of RP.

Solution phase synthesis of the less-known Form II crystalline red phosphorus

“…27 The nanorod II was occasionally abbreviated as n2, 5 but sometimes referred to as Type II as well. 15,16,75,76 This may erroneously lead to confusion between nanorod II and crystalline Form II. 15,16,75 Thus, it is necessary to clarify that the three nanorods and Form I to III are two sets of completely different red phosphorus allotropes, in which case there is no solid evidence showing that Form I to III with limited structural information could match any of the three nanorods whose lattice parameters and atomic coordinates are well defined.…”

“…7,15 Hence, only limited structural and morphological knowledge has been acquired on Form II RP today due to the difficulty of its single crystal growth. 16 Among all the preparation strategies for crystalline red phosphorus, high-temperature vapor phase methods still vastly dominate the field. 15,[17][18][19][20] The products synthesized through sealed ampoules are usually highly crystalline, 21 uniformly deposited 22,23 and closely brought into contact with substrates.…”

“…7,15 Hence, only limited structural and morphological knowledge has been acquired on Form II RP today due to the difficulty of its single crystal growth. 16…”

Atomically Dispersed Janus Nickel Sites on Red Phosphorus for Photocatalytic Overall Water Splitting

“…Figure 7a shows the geometric structure of red phosphorous with P−Ni and P−O−Ni sites and the corresponding *H adsorption geometries. Although red phosphorous appears as an amorphous phase, it has been widely accepted that its structure is based on tubular components of five‐ or six‐membered rings with covalent bonds between the P atoms [8d] . We, therefore, selected the type IV triclinic fibrous RP (001) surface as the model for theoretical calculations.…”

Boosting charge separation in conjugated microporous polymers via fluorination for enhancing photocatalysis

“…The last decades have witnessed that photocatalytic transformations have made remarkable advancements in solving the energy crisis and environmental issues. 1–5 Small-molecule organic dyes or ruthenium-/iridium-based transition-metal semiconductors are the commonly used homogeneous photocatalysts. 6–13 However, these homogeneous photocatalysts have some inherent disadvantages such as high toxicity, high price, scarcity, photobleaching under aerobic conditions, and difficulty to be removed.…”