Mass Activity Elucidation of Cobalt‐Based Oxygen Evolution Catalysts Utilizing Depth‐Resolved Spectroscopy in the Presence of Various Cations with ChlorideKomiya, Hiroki; Obata, Keisuke; Sekizawa, Oki; Nitta, Kiyofumi; Xu, Ke; Wada, Melody; Takanabe, Kazuhiro
doi: 10.1002/anie.202501579pmid: 39898994
The oxygen evolution reaction (OER) in water electrolysis is a kinetically sluggish reaction that requires catalysts with high electrocatalytic activity. Cobalt oxide (CoOx) is among the best performing OER catalysts and has been reported to have “bulk activity” with active sites distributed within the material. Herein, we examined the distribution of OER activity over μg cm−2 loaded CoOx deposited on anti‐corrosive Ti substrate in 1 M KOH with and without various cations with chloride (X−Cl, X=Li, Na, K). Depth‐resolved X‐ray absorption spectroscopy and depth‐profiling X‐ray photoelectron spectroscopy were employed. In a thin sample with ~20 nm thickness, uniform oxidation was observed, but a thicker sample with ~80 nm thickness had active oxidized phases close to the surface and an unexpected inactive Co0 phase concurrently occupying about three‐quarters of the CoOx layer in the depth direction, which accounted for the mass activity loss. The formation of Co0 in the bulk is attributed to the galvanic replacement reaction between CoOx and the metallic Ti substrate, which is not observed on the carbon substrate. Operando Raman spectroscopy demonstrated that the type of cations rather than Cl− impacts the OER performance likely due to their interaction with superoxo species.
Synergistic Zn and MoS2 Tailored Co−N/C Environments Enabling Bifunctional ORR/OER Electrocatalysis for Advanced Li−O2 BatteriesWang, Zhiyang; Zhang, Qi; Liu, Wenhong; Luo, Hao; Kong, Xianghua; Yang, Qingchun; Zhang, Dawei; Yu, Yan
doi: 10.1002/anie.202425502pmid: 39921426
To better adapt lithium‐oxygen batteries (LOBs) and overcome their sluggish oxygen reduction and evolution reactions (ORR/OER) kinetics, designing efficient bifunctional ORR/OER catalytic materials is essential. In this study, we successfully constructed a bifunctional ZnCo−N/C@MoS2 catalyst by tailoring the Co−N/C center with Zn incorporation and MoS2 encapsulation. Surprisingly, Zn atoms, which are typically considered to promote the Co atoms isolation, exhibit a promoting effect on the ORR performance of Co−N/C centers and enhance their stability under harsh conditions. Introducing MoS2 establishes Mo−N coupling centers, enhancing electron transfer and adjusting the charge density of Co active centers, thereby compensating OER activity limitation of ZnCo−N/C. In Li−O2 batteries, Zn and MoS2 synergistically optimize intermediate interactions and regulate LiO2 formation/decomposition, while Zn′s environmental adaptability and MoS2′s encapsulating protection jointly enhance operational stability. Results show that ZnCo−N/C@MoS2, serving as the oxygen electrode in Li−O2 batteries, achieves a low overpotential of 1.01 V, an ultra‐high specific capacity of 25,026 mAh g−1, and a long cycle life of 298 cycles. This work achieves bifunctionality in single‐atom catalysts through precise dual modulation of the catalytic environment, providing a novel strategy for the development of lithium‐oxygen batteries.
Hydrogenation of Organic Molecules via Direct MechanocatalysisMayer, Maike; Wohlgemuth, Maximilian; Salomé Straub, Anastasia; Grätz, Sven; Borchardt, Lars
doi: 10.1002/anie.202424139pmid: 39912800
Mechanochemical hydrogenation of unsaturated C−C and C−O, as well as N−O and C−X bonds is successfully achieved without the use of solvents, ligands, or catalyst powders via ball milling. A variety of catalysts are electroplated onto the walls of the milling vessel, allowing for simple recycling and reuse of the catalytic material. Hydrogen gas is directly introduced into the milling vessel, eliminating the need for hydrogen donor compounds which contribute to waste production and suboptimal atom economy. This approach enables the quantitative hydrogenation of unsaturated carbon‐carbon bonds, achieving near‐complete conversion within just 20 minutes at ambient temperature and pressures as low as 1.5 bar. Carbonyls, nitro groups, and organohalides were converted within reaction times of up to 12 hours. Mechanistic investigations suggest the reaction to be following established mechanisms for hydrogenation. Finally, chemoselective hydrogenation of various reducible functional groups was explored, demonstrating the versatility and efficiency of this solvent‐free mechanochemical approach with simple catalyst recycling for hydrogenation reactions.
Ligand‐Enabled Nondirected and Regioselective Arylation of Internal Alkenes with Simple ArenesLiu, Tianming; Deng, Xi; Gao, Yue; Li, Haofan; Du, Yu; Su, Weiping
doi: 10.1002/anie.202420443pmid: 39921548
Regioselective functionalization of internal alkenes has become a highly efficient approach for preparing stereochemically defined multi‐substituted olefins. Unlike traditional methods that require directing groups, activating groups, or active chemical bonds (e.g., halide, pseudo halide, organometallic reagent, etc.), there remains a strong demand for nondirected and selective functionalization of unactivated alkenes with simple coupling partners, both in academic research or industrial applications. Herein, we report the development of a pyridone‐oxazoline (Pyoox) type ligand that combines the features of both pyridone and pyridine‐oxazoline in assisting Pd‐catalyzed olefination. This ligand enables the activation of simple (hetero) arenes and internal alkenes within a single reaction system. A nondirected and regioselective arylation from simple raw materials has been achieved, providing a straightforward route to various trisubstituted olefins in moderate to excellent yields, with excellent regio‐/stereocontrol. Experimental and computational studies on mechanisms offer insight into the distinctive properties and performance of this ligand‐promoted catalysis. The synthetic utility of this method is further demonstrated by the simplified synthesis and late‐stage diversification of bioactive molecules.
Photo‐Patternable and Healable Polymer Semiconductor Enabled by Dynamic Covalent Disulfide BondingXue, Xiang; Li, Cheng; Yu, Xiaobo; Chenchai, Kaiyuan; Zhang, Xinyue; Zhang, Xisha; Zhang, Guanxin; Zhang, Deqing
doi: 10.1002/anie.202425172pmid: 39953764
Apart from charge transport property, polymer semiconductors with patternable and healable functions are highly demanding for the fabrication of organic circuits. Herein, by leveraging the dynamic covalent disulfide bonding of thioctic acid (TA) groups, we successfully integrate photo‐patterning and thermal‐healing capabilities into a single diketopyrrolopyrrole (DPP)‐based polymer semiconductor for the first time. The results show that the thin film of DPP‐based conjugated donor‐acceptor polymer with TA groups in the side chains exhibits excellent photo‐patterning capability under 365 nm UV light irradiation, with sensitivity (S) of 210 mJ⋅cm−2 and contrast (γ) of 1.2. Importantly, the patterning process has minimal impact on thin film morphology, interchain stacking, and charge transport mobility. Moreover, the patterned thin films, which were initially scratched, can be well healed after exposure to chloroform vapor and further thermal annealing, and simultaneously the charge mobility can be restored. In comparison, the scratched thin film of PDPP4T without TA groups in the side chains achieves only 82.6 % recovery of scratch depth and 54.5 % recovery of charge mobility under the same conditions. These results demonstrate the feasibility of constructing multifunctional polymer semiconductors by incorporating TA groups in the side chains, offering a new pathway to lithography‐compatible, self‐healing smart flexible devices.
Transient Dangling Active Sites of Fe(III)−N−C Single‐Atom Catalyst for Efficient Electrochemical CO2 Reduction ReactionQiu, Yun‐Ze; Liu, Xiao‐Meng; Li, Wenying; Li, Jun; Xiao, Hai
doi: 10.1002/anie.202424150pmid: 39900539
The Fe single‐atom catalyst (SAC) with an oxidation state of III anchored on the N‐doped carbon substrate (Fe(III)−N−C) delivers superior activity for catalyzing the electrochemical CO2 reduction reaction (eCO2RR) to produce CO, but its mechanism remains contentious and the commonly adopted FeN4‐C model is not a conformant model for Fe(III)−N−C but for Fe(II)−N−C. Herein, employing the grand‐canonical ensemble modeling with the density functional theory method benchmarked against the high‐level wavefunction theory method, we first identify the conformant model for Fe(III)−N−C to be FeN1C3‐C, and we then unveil that the Fe(III)N1C3‐C SAC generates a novel type of dangling active site transiently under working conditions, in which the Fe single‐atom leaves from the anchoring site by breaking all the Fe−C bonds but retains a stable binding to the substrate by the Fe−N bond. Thus, we further elucidate that this flexible dangling active site of Fe(III)−N−C renders a convoluted reaction network with facile CO2 activation, which delivers superior activity for eCO2RR. Our findings provide a novel understanding of the structure–activity relationship for Fe−N−C and concrete insights into the design of highly active SACs.
Spatially Separated Redox Centers in Anthraquinone‐grafted Metal‐Organic Frameworks for Efficient Piezo‐photocatalytic H2O2 ProductionChen, Cheng; Gu, Kaiye; Wang, Peifang; Liu, Zhao‐Qing; Ao, Yanhui
doi: 10.1002/anie.202425656pmid: 39910640
Piezo‐photocatalytic production of hydrogen peroxide (H2O2) from water and air is promising but its large‐scale application is still challenging as insufficient reaction active sites and low reaction efficiency. We have applied molecular engineering methods to design an anthraquinone molecularly (AQ) grafted metal–organic framework piezo‐photocatalyst (UiO‐66‐AQ) for H2O2 generation from water and air. The catalyst achieves a peak H2O2 yield of 7872.4 μM g−1 h−1 by facilitating two critical reactions: single‐electron water oxidation (WOR) and two‐electron oxygen reduction (ORR) on spatially separated redox sites. Experiments and computational simulations reveal efficient charge separation through a ligand‐to‐chain transfer mechanism. Electrons and holes are selectively transferred to AQ and UiO‐66 promoting ORR and WOR under ultrasound and visible light. The high reaction rate of ORR (rapid generation of endoperoxide) compensates for the slow kinetics of WOR (generation of OH*) and greatly increases the rate of full‐reaction of H2O2 production. Additionally, a continuous flow tubular reactor equipped with UiO‐66‐AQ catalytic membranes affords 96 % removal of organic dyes by a in situFenton process under visible light and water flow, confirming the significant potential of the catalyst for practical applications. This work deepens the understanding of directional carrier migration at piezo‐photocatalytic spatial separation sites, opening new pathways for environmentally friendly and efficient H2O2 synthesis.