The Use of Redox Mediators in Electrocatalysis and Electrosynthesis

Abstract

Electrocatalysis and electrosynthesis, which convert the electrical energy and store them in the chemical forms, have been considered as promising technologies to utilize green renewable energy sources. Most of the studies focused on developing novel active molecules or advanced electrodes to improve the performance. However, the direct acquisition and electron transferring will be limited by the intrinsic characters of the electrodes. The introduce of redox media-tors, which are served as the intermediate electron carriers or reservoirs without changing the final products, provide a unique approach to accelerate the electrochemical performance of these energy conversions. This review provides an overview of the recent development of electrocatalysis and electrosynthesis by using redox mediators, and provides a comprehensive discussion toward focusing on the principles and construction of these systems.

Frontiers in Photoelectrochemical Catalysis: A Focus on Valuable Product Synthesis

“…While the use of redox mediators in electrocatalytic and PEC synthesis of valuable chemicals is still ongoing research, several key factors are sought to influence the performances. [ 21 ] First, the alignment of the thermodynamic redox potential of the mediator with respect to the energy level of the semiconductor photoelectrode is essential, since it determines the possibility of the photogenerated electrons to be directly transferred to the mediator. Apart from this, the electrolyte pH, solubility of the mediator in the given electrolyte, and the reversibility of the mediator are very crucial factors that should be considered in choosing mediators.…”

“…For further understanding of the nature and properties of common redox mediators, we direct the readers to refer to previously communicated reviews. [21] The PEC processes compiled in this review focus on the reduction or oxidation of several kinds of feedstocks involving both direct and indirect PEC processes. a) Pyridine is added to abstract proton from N-hydroxysuccinimide.…”

Vanadium-Mediated High Areal Capacity Zinc–Manganese Redox Flow Battery

“…Even with the addition of excess bromine to achieve a higher capacity (approximately 30 mA h cm –2 ), the primary capacity is still provided by bromine itself (exceeding 20 mA h cm –2 ), and the contribution of MnO 2 to the capacity is very limited. Therefore, it is critical to select a new RM in an appropriate acidic environment to achieve an efficient deposition/dissolution reaction of MnO 2 in high areal capacity. − normalM n 2 + + 2 H 2 normalO ⇌ M n O 2 + 4 H + + 2 e − E 0 = 1.228 .25em normalV .25em v s .25em S H E normalZ n 2 + + 2 e − ⇌ Z n E 0 = prefix− 0.763 .25em normalV .25em v s .25em S H E Herein, a Zn–Mn 2+ /MnO 2 RFB (ZMRFB) was constructed based on the vanadium-mediated high areal capacity of the cathode with relatively high energy efficiency. , Benefiting from the high redox potential of Mn 2+ /MnO 2 couple and the relatively low potential of Zn/Zn 2+ (−0.763 V vs SHE, eq ), the battery achieved an ideal output voltage of nearly 2.0 V. To address the challenge of “dead” MnO 2 in high areal capacity applications, VO 2+ /VO 2 + redox couple with a standard potential of 0.98 V (vs SHE) close to that of Mn 2+ /MnO 2 is introduced as RM here. During discharge, partial MnO 2 is initially reduced to Mn 2+ , followed by the reduction of VO 2 + to VO 2+ .…”

Challenges and opportunities on sustainable electrochemical transformations: application towards the synthesis of pharmaceuticals and precursors of drug-like molecules

“…7 This review shall merge all of the recent developments made in the area of electrochemical pathways to drug analogues and value-added products, and pharmaceuticals. 6–10 Interestingly, electrochemistry has significantly shortened the synthetic routes to various pharmaceuticals and drug-like molecules, as highlighted in Fig. 1.…”