Solar‐to‐chemical energy conversion, or so‐called artificial photosynthesis, is a promising technology enabling sustainable production and use of various chemical compounds such as H2, CO, CH4, HCOOH, CH3OH, and NH3. For practical applications, it is necessary to improve the interfacial properties of light‐harvesting semiconductors through modification with proper electrocatalysts, by trying to overcome their intrinsic limitations such as rapid recombination, sluggish reaction kinetics, and photocorrosion. Compared to their heterogeneous counterparts, molecular electrocatalysts have a higher catalytic activity and more flexibility in their design/synthesis and integration with semiconducting materials. In this article, we review recent efforts on the tailored assembly of molecular electrocatalysts to address the above issues for artificial photosynthesis, especially those for oxygen evolution reactions on semiconductor photoelectrodes for photoelectrochemical water oxidation. One can expect that the strategies and methods developed for the tailored assembly and integration of molecular electrocatalysts on water oxidation photoanodes can provide insights for the design and fabrication of various forms of photosynthetic devices due to the similarity between their underlying principles.
Aqueous redox flow batteries (RFBs) have attracted significant attention as energy storage systems by virtue of their inexpensive nature and long‐lasting features. Although all‐vanadium RFBs exhibit long lifetimes, the cost of vanadium resources fluctuates considerably, and is generally expensive. Iron–chromium RFBs take advantage of utilizing a low‐cost and large abundance of iron and chromite ore; however, the redox chemistry of CrII/III generally involves strong Jahn–Teller effects. Herein, this work introduces a new Cr‐based negolyte coordinated with strong‐field ligands capable of mitigating strong Jahn–Teller effects, thereby facilitating low redox potential, high stability, and rapid kinetics. The balanced full‐cell configuration features a stable lifetime of 500 cycles with energy density of 14 Wh L−1. With an excessive posolyte, the full‐cell can attain a high energy density of 38.6 Wh L−1 as a single electron redox process. Consequently, the proposed system opens new avenues for the development of high‐performance RFBs.
This paper presents a compact resistor-based CMOS temperature sensor intended for dense thermal monitoring. It is based on an RC poly-phase filter (PPF), whose temperaturedependent phase shift is read out by a frequency-locked loop (FLL). The PPF's phase shift is determined by a zero-crossing detector, allowing the rest of the FLL to be realized in an areaefficient manner. Implemented in a 65-nm CMOS technology, the sensor occupies only 7000 µm 2. It can operate from supply voltages as low as 0.85 V, and consumes 68 µW. A sensor based on a PPF made from silicided p-poly resistors and MIM capacitors achieves an inaccuracy of ±0.12 • C (3σ) from-40 to 85 • C, and a resolution of 2.5 mK (rms) in a 1-ms conversion time. This corresponds to a resolution figure-of-merit of 0.43 pJ•K 2 .
Aqueous redox flow batteries (RFBs) have emerged as promising largescale energy storage devices due to their high scalability, safety, and flexibility. Manganese-based redox materials are promising sources for use in RFBs owing to their earth abundance, affordability, and variety of oxidation states. However, the instability of Mn redox couples, attributed to the unstable d-orbital configuration of Mn 3+ (d 4 ) known to involve strong Jahn−Teller effects, has hindered their practical use. Here, we discover that the [Mn(CN) 6 ] 5−/4−/3− negolyte offers advantages in terms of reversibility, stability, and reaction kinetics owing to the addition of NaCN supporting electrolyte, which inhibits ligand exchange reactions, resulting in high performance. [Mn(CN) 6 ] 5−/4−/3− negolyte possesses stable multielectron reactions from Mn(I) to Mn(III), leading to a high capacity of 133.7 mAh after 100 cycles. We provide chemical evidence obtained from in situ Raman analysis for unprecedented Mn(I) stability during electrochemical cycling, opening up new avenues for the design of low-cost Mn-based redox systems.
Aqueous redox flow batteries (RFBs) have attracted significant attention as energy storage systems by virtue of their inexpensive nature and long-lasting features. Although all-vanadium RFBs exhibit long lifetimes, the cost of vanadium resources fluctuates considerably, and is generally expensive. Iron–chromium RFBs take advantage of utilizing a low-cost and large abundance of iron and chromite ore; however, the redox chemistry of CrII/III generally involves strong Jahn–Teller effects. Herein, we introduce a new Cr-based negolyte coordinated with strong-field ligands capable of mitigating strong Jahn–Teller effects, thereby facilitating low redox potential, high stability, and rapid kinetics. Density functional theory (DFT) calculations reveal that the complex of [Cr(CN)6]4− prefers low-spin states, facilitating a stable and fast redox reaction. The prototype full-cell configuration features a high-energy density of 11.4 Wh L− 1 and a stable lifetime of 250 cycles. Consequently, our proposed system opens new avenues for the development of high-performance RFBs.
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