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Due to the robust oxidation conditions in strong acid oxygen evolution reaction (OER), developing an OER electrocatalyst with high efficiency remains challenging in polymer electrolyte membrane (PEM) water electrolyzer. Recent theoretical research suggested that reducing the coordination number of Ir−O is feasible to reduce the energy barrier of the rate‐determination step, potentially accelerating the OER. Inspired by this, we experimentally verified the Ir−O coordination number's role at model catalysts, then synthesized low‐coordinated IrOx nanoparticles toward a durable PEM water electrolyzer. We first conducted model studies on commercial rutile‐IrO2 using plasma‐based defect engineering. The combined in situ X‐ray absorption spectroscopy (XAS) analysis and computational studies clarify why the decreased coordination numbers increase catalytic activity. Next, under the model studies' guidelines, we explored a low‐coordinated Ir‐based catalyst with a lower overpotential of 231 mV@10 mA cm−2 accompanied by long durability (100 h) in an acidic OER. Finally, the assembled PEM water electrolyzer delivers a low voltage (1.72 V@1 A cm−2) as well as excellent stability exceeding 1200 h (@1 A cm−2) without obvious decay. This work provides a unique insight into the role of coordination numbers, paving the way for designing Ir‐based catalysts for PEM water electrolyzers. [ABSTRACT FROM AUTHOR]

The high cost of noble metals is one of the key factors hindering the large‐scale application of proton exchange membrane (PEM) water electrolyzer for hydrogen production. Recently, single‐atom catalysts (SACs) with a potential of maximum atom utilization efficiency enable lowering the metal amount as much as possible; unfortunately, their durability remains a challenge under PEM water electrolyzer working conditions. Herein, a highly‐stable alloyed Pt SAC is demonstrated through a plasma‐assisted alloying strategy and applies to a PEM water electrolyzer. In this catalyst, single Pt atoms are firmly anchored onto a Ru support via a robust metal–metal bonding strength, as evidenced by these complementary characterizations. This SAC is used in a PEM water electrolyzer system to achieve a cell voltage as low as 1.8 V at 1000 mA cm−2. Impressively, it can operate over 1000 h without obvious decay, and the catalyst is present in the form of individual Pt atoms. To the knowledge, this will be the first SAC attempt at a cell level toward long‐term PEM. This work paves the way for designing durable SACs employed in the actual working condition in the PEM water electrolyzer. [ABSTRACT FROM AUTHOR]

Recharging batteries operate at sub‐zero temperature is usually limited by the slow ion diffusion and uneven charge distribution at low temperature. Here, we report a strategy to regulate electric field and thermal field simultaneously, creating a fast and uniform deposition surroundings for potassium ion in potassium metal batteries (PMBs). This regulation is achieved by using a highly ordered 1D nanoarray electrode which provides a dense and flat surface for uniforming the electric field and high thermal conductivity for reducing the temperature fluctuation. Consequently, this electrode could achieve high‐areal capacity of 10 mAh cm−2. Besides, the dependence of potassium nucleation on temperature is unveiled. Furthermore, a full‐cell could steady operate with over 80 % of its room‐temperature capacity at −20 °C. Those respectable performances demonstrate that this strategy is valid, potentially providing guidelines for the rational design of advanced electrodes toward PMBs. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts (SACs) with a maximum atom utilization efficiency have received growing attention in heterogeneous catalysis. The supporting substrate that provides atomic‐dispersed anchoring sites and the local electronic environment in these catalysts is crucial to their activity and stability. Here, inspired by N‐doped graphene substrate, the role of N is explored in transition metal nitrides for anchoring single metal atoms toward single‐atom catalysis. A pore‐rich metallic vanadium nitride (VN) nanosheet is fabricated as one supporting‐substrate example, whose surface features abundant unsaturated N sites with lower binding energy than that of widely used N‐doped graphene. Impressively, it is found that this support can anchor nearly all platinum‐group single atoms (e.g., platinum, palladium, iridium, and ruthenium), and even be extendable to multiple SACs, i.e., binary (Pt/Pd) and ternary (Pt/Pd/Ir). As a proof‐of‐concept application for hydrogen production, Pt‐based SAC (Pt1‐VN) performs excellently, exhibiting a mass activity up to 22.55 A mg−1Pt at 0.05 V and a high turnover frequency value close to 0.350 H2 s−1, superior to commercial platinum/carbon catalyst. The catalyst's durability can be further improved by using binary (Pt1Pd1‐VN) SAC. This work provides inexpensive and durable nitride‐based support, giving a possible pathway for universally constructing platinum‐group SACs. [ABSTRACT FROM AUTHOR]

Carrier doping is the basis of the modern semiconductor industry. Great efforts are put into the control of carrier doping for 2D semiconductors, especially the layered transition metal dichalcogenides. Here, the direct laser patterning of WSe2 devices via light‐induced hole doping is systematically studied. By changing the laser power, scan speed, and the number of irradiation times, different levels of hole doping can be achieved in the pristine electron‐transport‐dominated WSe2, without obvious sample thinning. Scanning transmission electron microscopy characterization reveals that the oxidation of the laser‐radiated WSe2 is the origin of the carrier doping. Photocurrent mapping shows that after the same amount of laser irradiation, with increasing thickness, the laser patterned PN junction changes from the pure lateral to the vertical‐lateral hybrid structure, accompanied by the decrease in the open circuit voltage. The vertical‐lateral hybrid PN junction can be tuned to a pure lateral one by further irradiation, showing possibilities to construct complex junction profiles. Moreover, a NOR gate circuit is demonstrated by direct patterning of p‐doped channels using laser irradiation without introducing passive layers and metal electrodes with different work functions. This method simplifies device fabrication procedures and shows a promising future in large scale logic circuit applications. [ABSTRACT FROM AUTHOR]

Abstract: Low‐grade heat to electricity conversion has shown a large potential for sustainable energy supply. Recently, the low‐grade heat harvesting in the thermally regenerative electrochemical cycle (TREC) is a promising candidate with high energy conversion efficiency. In this system, the electrochemical temperature coefficient (α) plays a dominant role in efficient heat harvesting. However, the internal factors that affect α are still not clear and significant improvements are needed. Here, α of various Prussian Blue analogues (PBAs) is investigated and their lattice change during cation intercalation is monitored using the ex situ X‐ray diffraction (XRD) method. For the first time, it is found that α is highly related to the lattice parameter change. Large lattice shrinkage exhibits a large negative α, while lattice expansion is corresponding to a positive α. These are mainly attributed to the different phonon vibration entropy changes upon cation intercalation in various PBAs. Especially, purple cobalt hexacynoferrate delivers the largest α of −0.89 mV K−1 and enables highly efficient heat conversion efficiency up to 2.65% (21% of relative efficiency). The results of this study provide a fundamental understanding of temperature coefficient in electrochemical reactions and pave the way for designing high‐performance material for low‐grade heat harvesting. [ABSTRACT FROM AUTHOR]

The emergence of semiconducting transition metal dichalcogenide (TMD) atomic layers has opened up unprecedented opportunities in atomically thin electronics. Yet the scalable growth of TMD layers with large grain sizes and uniformity has remained very challenging. Here is reported a simple, scalable chemical vapor deposition approach for the growth of MoSe2 layers is reported, in which the nucleation density can be reduced from 105 to 25 nuclei cm−2, leading to millimeter-scale MoSe2 single crystals as well as continuous macrocrystalline films with millimeter size grains. The selective growth of monolayers and multilayered MoSe2 films with well-defined stacking orientation can also be controlled via tuning the growth temperature. In addition, periodic defects, such as nanoscale triangular holes, can be engineered into these layers by controlling the growth conditions. The low density of grain boundaries in the films results in high average mobilities, around ≈42 cm2 V−1 s−1, for back-gated MoSe2 transistors. This generic synthesis approach is also demonstrated for other TMD layers such as millimeter-scale WSe2 single crystals. [ABSTRACT FROM AUTHOR]