Abstract
The increasing interest and applications of photocatalysis, namely hydrogen production, artificial photosynthesis, and water remediation and disinfection, still face several drawbacks that prevent this technology from being fully implemented at the industrial level. The need to improve the performance of photocatalytic processes and extend their potential working under visible light has boosted the synthesis of new and more efficient semiconductor materials. Thus far, semiconductor–semiconductor heterojunction is the most remarkable alternative. Not only are the characteristics of the new materials relevant to the process performance, but also a deep understanding of the charge transfer mechanisms and the relationship with the process variables and nature of the semiconductors. However, there are several different charge transfer mechanisms responsible for the activity of the composites regardless the synthesis materials. In fact, different mechanisms can be carried out for the same junction. Focusing primarily on the photocatalytic generation of hydrogen, the objective of this review is to unravel the charge transfer mechanisms after the in-depth analyses of already reported literature and establish the guidelines for future research.
Highlights
Semiconductor-based photocatalysis has attracted great attention in recent decades because of its potential to contribute to solve worldwide environmental and energy issues
A more efficient catalyst with widened light absorption spectrum is obtained. This topic has been addressed in several review works such as Wang et al [28], Moniz et al [29], Yang et al [30], and Fajrina et al [31], who reported the synthesis and properties of different semiconductor–semiconductor heterojunctions
The promising results obtained so far with semiconductor–semiconductor heterojunctions motivate discerning the charge transfer mechanisms responsible for the enhanced performance in order to drive the design of more efficient processes for photocatalytic hydrogen generation
Summary
Semiconductor-based photocatalysis has attracted great attention in recent decades because of its potential to contribute to solve worldwide environmental and energy issues. A more efficient catalyst with widened light absorption spectrum is obtained This topic has been addressed in several review works such as Wang et al [28], Moniz et al [29], Yang et al [30], and Fajrina et al [31], who reported the synthesis and properties of different semiconductor–semiconductor heterojunctions. Kandi et al [32] and Rao et al [33] gathered several references about the exceptional properties of using quantum dots to boost photocatalytic activity where the authors highlighted the quantum confinement effect of emitting multiple electrons, size-adjustable properties such as light absorption, and the benefits of quantum dot-semiconductor heterojunctions, especially in hydrogen production [34]. The promising results obtained so far with semiconductor–semiconductor heterojunctions motivate discerning the charge transfer mechanisms responsible for the enhanced performance in order to drive the design of more efficient processes for photocatalytic hydrogen generation. This work is mainly focused on photocatalytic hydrogen generation, when necessary, other motivated applications have been considered
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