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Anion-exchange-membrane fuel cells (AEMFCs) are a cost-effective alternative to proton-exchange-membrane fuel cells (PEMFCs). The development of high-performance and durable AEMFCs requires highly conductive and robust anion-exchange membranes (AEMs). However, AEMs generally exhibit a trade-off between conductivity and dimensional stability. Here, a fluorination strategy to create a phase-separated morphological structure in poly(aryl piperidinium) AEMs is reported. The highly hydrophobic perfluoroalkyl side chains augment phase separation to construct interconnected hydrophilic channels for anion transport. As a result, these fluorinated PAP (FPAP) AEMs simultaneously possess high conductivity (>150 mS cm(-1) at 80 degrees C) and high dimensional stability (swelling ratio 80 MPa and elongation at break >40%) and chemical stability (>2000 h in 3 m KOH at 80 degrees C). AEMFCs with a non-precious Co-Mn spinel cathode using the present FPAP AEMs achieve an outstanding peak power density of 1.31 W cm(-2). The AEMs remain stable over 500 h of fuel cell operation at a constant current density of 0.2 A cm(-2).

The reaction of carbon dioxide with hydroxide to form carbonate in near neutral or alkaline medium severely limits the energy and carbon efficiency of CO2 electroreduction. Here we show that by suppressing the otherwise predominant hydrogen evolution using alkali cations, efficient CO2 electroreduction can be conducted in acidic medium, overcoming the carbonate problem. The cation effects are general for three typical catalysts including carbon supported tin oxide, gold, and copper, leading to Faradaic efficiency of as high as 90% for formic acid and CO formation. Our analysis suggests hydrated alkali cations physisorbed on the cathode modify the distribution of electric field in the double layer, which impedes hydrogen evolution by suppress the migration of hydronium ions while at the same time promotes CO2 reduction by stabilizing key intermediates.

Compounds rich in sp(3)-hybridized carbons are desirable in drug discovery. Nickel-catalyzed hydrocarbonation of alkenes is a potentially efficient method to synthesize these compounds. By using abundant, readily available, and stable alkenes as pro-nucleophiles, these reactions can have broad scope and high functional group tolerance. However, this methodology is still in an early stage of development, as the first efficient examples were reported only in 2016. Herein, we summarize the progress of this emerging field, with an emphasis on enantioselective reactions. We highlight major developments, critically discuss a wide range of possible mechanisms, and offer our perspective of the state and challenges of the field. We hope this Perspective will stimulate future works in this area, making the methodology widely applicable in organic synthesis.

The oxygen evolution reaction (OER) is the bottleneck reaction of water splitting, which can be used to generate green hydrogen from renewable electricity. Cobalt iron oxyhydroxides (CoFeOxHy) are among the most active OER catalysts in alkaline medium. However, the active sites of these catalysts remain unclear. Here we use operando ultraviolet-visible (UV-Vis), X-ray absorption, and Raman spectroscopy to reveal oxidations of both Fe and Co ions in CoFeOxHy during the OER. By analyzing samples with different Fe contents and thickness, we find that the concentration of Fe4+ species at the surface, but not the concentration of Co4+ in the bulk, scales with the catalytic activity. These results indicate an Fe4+-containing active site in CoFeOxHy.

Intermolecular functionalization of C(sp3)-H bonds and aliphatic carboxylic acids enables the efficient synthesis of high value-added organic compounds from readily available starting materials. Although methods involving hydrogen atom transfer have been developed for such functionalization, these methods either work for only activated C(sp3)-H bonds or bring in a narrow set of functional groups. Here we describe a Cu-catalyzed process for the diverse functionalization of both unactivated C(sp3)-H bonds and aliphatic carboxylic acids. The process is enabled by the trapping of alkyl radicals generated through hydrogen atom abstraction by arylsulfonyl-based SOMO-philes, which introduces a large array of C, N, S, Se, and halide-based functional groups. The chemoselectivity can be switched from C-H functionalization to decarboxylative functionalization by matching the bond dissociation energy of the hydrogen atom transfer reagent with that of the target C-H or O-H bond.

The linear scaling relationship of the binding energies of different intermediates limits the catalyst performance in CO

Hydroxide exchange membrane fuel cell (HEMFC) is a potentially cost-effective energy conversion technology. However, current state of the art HEMFCs require a high loading of platinum-group-metal (PGM) catalysts, especially for the hydrogen oxidation reaction (HOR). Here we develop a porous nitrogen-doped carbon-supported PtRu HOR catalyst (PtRu/pN-C) that has the highest reported intrinsic and mass activity in alkaline condition. Spectroscopic and microscopic data indicate the presence of Pt single atoms (SAs) in addition to PtRu nanoparticles on pN-C. Mechanistic study suggests Ru modulates the electronic structure of Pt for an optimized hydrogen binding energy, while Pt-SAs on pN-C optimize the interfacial water structure. These synergetic interactions are responsible for the high catalytic activity of this catalyst. An HEMFC with a low loading of this catalyst and a commercial Fe-N-C oxygen reduction reaction (ORR) catalyst achieves the highest reported PGM utilization rate. The current density at 0.65 V of this HEMFC reaches 1.5 A/cm2, exceeding the US DOE 2022 target (1 A/cm2) by 50 %.

In the biosynthesis of the iron-guanylylpyridinol (FeGP) cofactor, 6-carboxymethyl-5-methyl-4-hydroxy-2-pyridinol (1) is 3-methylated to form 2, then 4-guanylylated to form 3, and converted into the full cofactor. HcgA-G proteins catalyze the biosynthetic reactions. Herein, we report the function of two radical S-adenosyl methionine enzymes, HcgA and HcgG, as uncovered by in vitro complementation experiments and the use of purified enzymes. In vitro biosynthesis using the cell extract from the Methanococcus maripaludis Delta hcgA strain was complemented with HcgA or precursors 1, 2 or 3. The results suggested that HcgA catalyzes the biosynthetic reaction that forms 1. We demonstrated the formation of 1 by HcgA using the 3 kDa cell extract filtrate as the substrate. Biosynthesis in the Delta hcgG system was recovered by HcgG but not by 3, which indicated that HcgG catalyzes the reactions after the biosynthesis of 3. The data indicated that HcgG contributes to the formation of CO and completes biosynthesis of the FeGP cofactor.

The reconstitution of [Mn]‐hydrogenases using a series of MnI complexes is described. These complexes are designed to have an internal base or pro‐base that may participate in metal–ligand cooperative catalysis or have no internal base or pro‐base. Only MnI complexes with an internal base or pro‐base are active for H2 activation; only [Mn]‐hydrogenases incorporating such complexes are active for hydrogenase reactions. These results confirm the essential role of metal–ligand cooperation for H2 activation by the MnI complexes alone and by [Mn]‐hydrogenases. Owing to the nature and position of the internal base or pro‐base, the mode of metal–ligand cooperation in two active [Mn]‐hydrogenases is different from that of the native [Fe]‐hydrogenase. One [Mn]‐hydrogenase has the highest specific activity of semi‐synthetic [Mn]‐ and [Fe]‐hydrogenases. This work demonstrates reconstitution of active artificial hydrogenases using synthetic complexes differing greatly from the native active site., A series of [Mn]‐hydrogenases were reconstituted using specifically designed MnI complexes. In two catalytically active [Mn]‐hydrogenases, the mode of metal–ligand cooperation is different from that of the native [Fe]‐hydrogenase. One such [Mn]‐hydrogenase exhibits the highest specific activity among all known semi‐synthetic [Mn]‐ and [Fe]‐hydrogenases.

Oxidative amination of alkenes via amidyl radical addition is potentially an efficient method to generate allylic amines, which are versatile synthetic intermediates to bioactive compounds and organic materials. Here by combining photochemical generation of amidyl radicals with Cu-mediated β-H elimination of alkyl radicals, we have developed an intermolecular oxidative amination of unactivated alkenes. The reaction relies on tandem photoredox and copper catalysis, and works for both terminal and internal alkenes. The radical nature of the reaction and the mild conditions lead to high functional group tolerance., Oxidative amination via amidyl radical addition of unactivated alkenes was realized by dual photoredox and copper catalysis.

Hydroxide exchange membrane fuel cell (HEMFC) is a potentially cost-effective energy conversion technology. However, current state of the art HEMFCs require a high loading of platinum-group-metal (PGM) catalysts, especially for the hydrogen oxidation reaction (HOR). Here we develop a porous nitrogen-doped carbon-supported PtRu HOR catalyst (PtRu/pN-C) that has the highest reported intrinsic and mass activity in alkaline condition. An HEMFC with a low loading of this catalyst and a commercial Fe-N-C oxygen reduction reaction (ORR) catalyst achieves the highest reported PGM utilization rate. The current density at 0.65 V of this HEMFC reaches 1.5 A/cm2, exceeding the US DOE 2022 target (1 A/cm2) by 50 %. Spectroscopic and microscopic data indicate the presence of Pt single atoms (SAs) in addition to PtRu nanoparticles on pN-C. Mechanistic study suggests Ru modulates the electronic structure of Pt for an optimized hydrogen binding energy, while Pt-SAs on pN-C optimize the interfacial water structure. These synergetic interactions are responsible for the high catalytic activity of this catalyst.

An organic photoredox catalyst, 4CzIPN, was used in combination with a copper catalyst, CuCl, to effect decarboxylative C(sp3)–N coupling. The coupling worked with both anilines and imines as nitro...

The oxygen evolution reaction (OER) is the performance-limiting half reaction of water splitting, which can be used to produce hydrogen fuel using renewable energies. Whereas a number of transition metal oxides and oxyhydroxides have been developed as promising OER catalysts in alkaline medium, the mechanisms of OER onco these catalysts are not well understood. Here we combine electrochemical and in situ spectroscopic methods, particularly operando X-ray absorption and Raman spectroscopy, to study the mechanism of OER on cobalt oxyhydroxide (CoOOH), an archetypical unary OER catalyst. We find the dominating resting state of the catalyst as a Co(IV) species CoO2. Through oxygen isotope exchange experiments, we discover a cobalt superoxide species as an active intermediate in the OER. This intermediate is formed concurrently to the oxidation of CoOOH to CoO2. Combing spectroscopic and electrokinetic data, we identify the rate-determining step of the OER as the release of dioxygen from the superoxide intermediate. The work provides important experimental fingerprints and new mechanistic perspectives for OER catalysts.

A nickel-catalyzed reductive amidation of unactivated esters was recently reported, employing readily available and low-cost nitroarenes as nitrogen sources. Here, we describe a comprehensive exper...

Convergent paired electrosynthesis is an energy-efficient approach in organic synthesis; however, it is limited by the difficulty to match the innate redox properties of reaction partners. Here we use nickel catalysis to cross-couple the two intermediates generated at the two opposite electrodes of an electrochemical cell, achieving direct arylation of benzylic C–H bonds. This method yields a diverse set of diarylmethanes, which are important structural motifs in medicinal and materials chemistry. Preliminary mechanistic study suggests oxidation of a benzylic C–H bond, Ni-catalyzed C–C coupling, and reduction of a Ni intermediate as key elements of the catalytic cycle., A direct arylation of benzylic C–H bonds is achieved by integrating Ni-catalyzed benzyl–aryl coupling into convergent paired electrolysis.

Efficient catalytic water splitting demands advanced catalysts to improve the slow kinetics of the oxygen evolution reaction (OER). Earth-abundant transition metal oxides show promising OER activity in alkaline media. However, most experimental information available is either from post-mortem studies or in-situ space-averaged X-ray techniques in the micrometer range. Therefore, the composition of the active centers under operando conditions is still under debate. In this work, we combine nanoscopic and spectroscopic measurements on the hydroxylation of molecular beam epitaxy (MBE)-prepared Ni and NiFe oxides nanoislands with operando local investigations of Ni and NiFe hydroxide electrocatalysts under OER conditions to reveal the nature of active centers of Ni and Fe-doped Ni oxides in 2D OER catalysts. Our results reveal that Fe doping increases the active surface area by island fragmentation and boosts the intrinsic activity by creating optimized active centers consisting of both Ni and Fe atoms. In addition, our findings show that operando characterization at the nanoscale is crucial to reveal the dynamic nature of the interface of 2D catalysts under reaction conditions.

The electronic modulation of atomic dispersed active sites is promising to boost the catalytic activity, which is however remains a challenge. Here we show a cooperative Ni single-atom on nanoparticle catalyst (NiSA/NP) via direct solid-state pyrolysis, where Ni nanoparticles donate electrons to Ni(i)-N-C sites via carbon nanotubes network, achieving a high CO current density of 346 mA cm-2 at -0.5 V vs RHE in an alkaline flow cell. When coupled with a NiFe-based oxygen evolution anode into a zero-gap membrane electrolyzer, it delivers an industrial-relevant CO current density of 310 mA cm-2 at a low cell voltage of -2.3 V, corresponding to an overall energy efficiency of 57%. The superior CO2 electroreduction performance is attributed to the enhanced adsorption of key intermediate COOH* on electron-rich Ni single atom, together with the dense active sites.

In the FeGP cofactor of [Fe]-hydrogenase, low-spin Fe-II is in complex with two CO ligands and a pyridinol derivative; the latter ligates the iron with a 6-acylmethyl substituent and the pyridinol nitrogen. A guanylylpyridinol derivative, 6-carboxymethyl-3,5-dimethyl-4-guanylyl-2-pyridinol (3), is produced by the decomposition of the FeGP cofactor under irradiation with UV-A/blue light and is also postulated to be a precursor of FeGP cofactor biosynthesis. HcgC and HcgB catalyze consecutive biosynthesis steps leading to 3. Here, we report an in vitro biosynthesis assay of the FeGP cofactor using the cell extract of the Delta hcgB Delta hcgC strain of Methanococcus maripaludis, which does not biosynthesize 3. We chemically synthesized pyridinol precursors 1 and 2, and detected the production of the FeGP cofactor from 1, 2 and 3. These results indicated that 1, 2 and 3 are the precursors of the FeGP cofactor, and the carboxy group of 3 is converted to the acyl ligand.

Modulating the electronic structure of atomically dispersed active sites is promising to boost catalytic activity but is challenging to achieve. Here we show a cooperative Ni single-atom-on-nanoparticle catalyst (NiSA/NP) prepared via direct solid-state pyrolysis, where Ni nanoparticles donate electrons to Ni(i)-N-C sites via a network of carbon nanotubes, achieving a high CO current density of 346 mA cm

Oxidase-type oxidation is an attractive strategy in organic synthesis due to the use of O-2 as the terminal oxidant. Organic photocatalysis can effect metal-free oxidase chemistry. Nevertheless, current methods are limited in reaction scope, possibly due to the lack of suitable photocatalysts. Here we report an isoquinoline-derived diaryl ketone-type photocatalyst, which has much enhanced absorption of blue and visible light compared to conventional diaryl ketones. This photocatalyst enables dehydrogenative cross-coupling of heteroarenes with unactivated and activated alkanes as well as aldehydes using air as the oxidant. A wide range of heterocycles with various functional groups are suitable substrates. Transient absorption and excited-state quenching experiments point to an unconventional mechanism that involves an excited state "self-quenching" process to generate the N-radical cation form of the sensitizer, which subsequently abstracts a hydrogen atom from the alkane substrate to yield a reactive alkyl radical.

Anion-exchange membrane fuel cells (AEMFCs) are a promising, next-generation fuel cell technology. AEMFCs require highly conductive and robust anion-exchange membranes (AEMs), which are challenging to develop due to the tradeoff between conductivity and water uptake. Here we report a method to prepare high-molecular-weight branched poly(aryl piperidinium) AEMs. We show that branching reduces water uptake, leading to improved dimensional stability. The optimized membrane, b-PTP-2.5, exhibits simultaneously high OH

While solar-to-fuel catalysis requires the careful transfer of electrons, there are still challenges understanding how electron spin contributes to reactivity. Here, authors employ chiral fused thiadiazole-helicenes to control spin polarization in oxygen evolution electrocatalysts., A sustainable future requires highly efficient energy conversion and storage processes, where electrocatalysis plays a crucial role. The activity of an electrocatalyst is governed by the binding energy towards the reaction intermediates, while the scaling relationships prevent the improvement of a catalytic system over its volcano-plot limits. To overcome these limitations, unconventional methods that are not fully determined by the surface binding energy can be helpful. Here, we use organic chiral molecules, i.e., hetero-helicenes such as thiadiazole-[7]helicene and bis(thiadiazole)-[8]helicene, to boost the oxygen evolution reaction (OER) by up to ca. 130 % (at the potential of 1.65 V vs. RHE) at state-of-the-art 2D Ni- and NiFe-based catalysts via a spin-polarization mechanism. Our results show that chiral molecule-functionalization is able to increase the OER activity of catalysts beyond the volcano limits. A guideline for optimizing the catalytic activity via chiral molecular functionalization of hybrid 2D electrodes is given.

Electrocatalytic CO2 to CO conversion is approaching the industrial benchmark. Currently, Au electrodes show the best performance, whereas non-precious metal catalysts exhibit inferior activity. Here we show a densely populated Ni single-atom on nanoparticle catalyst (NiSA/NP) via direct solid-sate pyrolysis, where Ni nanoparticles donate electrons to Ni(i)-N-C sites via carbon nanotubes network, achieves a high CO current of 352 mA cm− 2 at -0.55 V vs RHE in an alkaline flow cell. When coupled with a NiFe-based oxygen evolution anode into a zero-gap membrane electrolyser, it delivers an industrial-relevant CO current of 310 mA cm− 2 at a low cell voltage of -2.3 V, corresponding to an overall energy efficiency of 57%. The superior CO2 electroreduction performance is attributed to the enhanced adsorption of key intermediate COOH* on electron-rich Ni single atom, together with the dense active sites.

Polyfluoroarenes are an important class of compounds in medical and material chemistry. The synthesis of alkylated polyfluoroarenes remains challenging. Here we describe a decarboxylative coupling reaction of N‐hydroxyphthalimide esters of aliphatic carboxylic acids with polyfluoroaryl zinc reagents (Zn‐ArF) via synergetic photoredox and copper catalysis. This method readily converts primary and secondary alkyl carboxylic acids into the corresponding polyfluoroaryl compounds, which could have a wide range of F‐content (2F‐5F) and variable F‐substitution patterns on the aryl groups. Broad scope and good functional group compatibility were achieved, including on substrates derived from natural products and pharmaceuticals. Mechanistic study revealed that a [Cu‐(ArF)2] species could be responsible for the transfer of polyfluoroaryl groups to the alkyl radicals., Decarboxylative coupling of aliphatic N‐hydroxyphthalimide esters with polyfluoroaryl zinc reagents was achieved by dual photoredox and copper catalysis. This method allows the installation of alkyl groups on polyfluoroaryls with a wide range of F‐content (2F‐5F) and variable F‐substitution patterns.

Carbosilylation of alkenes can be an efficient approach to the synthesis of organosilicon compounds. However, few general methods of carbosilylation are known. Here, we introduce a strategy for arylsilylation of electron deficient terminal alkenes by combining photoredox-catalyzed silyl radical generation, innate reactivity of silyl radical with alkene, and Ni-catalyzed aryl-alkyl cross-coupling. This cooperative photoredox and nickel catalysis operates under mild conditions. It employs readily available alkenes, aryl bromides, and silane as reagents, and it produces useful synthetic building blocks in a modular manner.

Nickel hydride (NiH) catalyzed hydrocarbonation has emerged as an efficient approach to construct new C-C bonds containing at least one C(sp3 ) center. However, the regioselectivity of this reaction is by far dictated by substrates. Described here is a strategy to achieve two different regioselectivites of hydroalkylation of the same substrates by using ligand control. This strategy enables the first regiodivergent hydroalkylation of 3-pyrrolines, yielding both 2- and 3-alkylated pyrrolidines, valuable synthetic intermediates and common motifs in many bioactive molecules. This method demonstrates broad scope and high functional-group tolerance, and can be applied in late-stage functionalizations.

Nickel iron oxide is considered a benchmark nonprecious catalyst for the oxygen evolution reaction (OER). However, the nature of the active site in nickel iron oxide is heavily debated. Here we report direct spectroscopic evidence for the different active sites in Fe‐free and Fe‐containing Ni oxides. Ultrathin layered double hydroxides (LDHs) were used as defined samples of metal oxide catalysts, and18O‐labeling experiments in combination with in situ Raman spectroscopy were employed to probe the role of lattice oxygen as well as an active oxygen species, NiOO−, in the catalysts. Our data show that lattice oxygen is involved in the OER for Ni and NiCo LDHs, but not for NiFe and NiCoFe LDHs. Moreover, NiOO−is a precursor to oxygen for Ni and NiCo LDHs, but not for NiFe and NiCoFe LDHs. These data indicate that bulk Ni sites in Ni and NiCo oxides are active and evolve oxygen via a NiOO−precursor. Fe incorporation not only dramatically increases the activity, but also changes the nature of the active sites.

Ketones are an important class of molecules in synthetic and medicinal chemistry. Rapid and modular synthesis of ketones remains in high demand. Described here is a nickel-catalyzed three-component reductive carbonylation method for the synthesis of dialkyl ketones. A wide range of both symmetric and asymmetric dialkyl ketones can be accessed from alkyl halides and a safe CO source, ethyl chloroformate. The approach offers complementary substrate scope to existing carbonylation methods while avoiding the use of either toxic CO or metal carbonyl reagents.

Nature carefully selects specific metal ions for incorporation into the enzymes that catalyze the chemical reactions necessary for life. Hydrogenases, enzymes that activate molecular H2, exclusively utilize Ni and Fe in [NiFe]-, [FeFe]-, and [Fe]-hydrogeanses. However, other transition metals are known to activate or catalyze the production of hydrogen in synthetic systems. Here, we report the development of a biomimetic model complex of [Fe]-hydrogenase that incorporates a Mn, as opposed to a Fe, metal center. This Mn complex is able to heterolytically cleave H2 as well as catalyze hydrogenation reactions. Incorporation of the model into an apoenzyme of [Fe]-hydrogenase results in a [Mn]-hydrogenase with enhanced occupancy-normalized activity over an analogous semi-synthetic [Fe]-hydrogenase. These findings represent the first instance of a non-native metal hydrogenase showing catalytic functionality and demonstrate that hydrogenases based on a manganese active site are viable.

The oxygen evolution reaction (OER) is a key process that enables the storage of renewable energies in the form of chemical fuels. Here, we describe a catalyst that exhibits turnover frequencies higher than state-of-the-art catalysts that operate in alkaline solutions, including the benchmark nickel iron oxide. This new catalyst is easily prepared from readily available and industrially relevant nickel foam, and it is stable for many hours. Operando X-ray absorption spectroscopic data reveal that the catalyst is made of nanoclusters of γ-FeOOH covalently linked to a γ-NiOOH support. According to density functional theory (DFT) computations, this structure may allow a reaction path involving iron as the oxygen evolving center and a nearby terrace O site on the γ-NiOOH support oxide as a hydrogen acceptor., A catalyst composed of nanoclusters of γ-FeOOH covalently linked to a γ-NiOOH support exhibits significantly higher activity in the oxygen evolution reaction than conventional nickel iron oxides.

Single-atom catalysts are emerging as primary catalysts for many reactions due to their 100% utilization of active metal centers leading to high catalytic efficiencies. Herein, we report the use of a single-atom Co catalyst for the oxidative cleavage of the β-O-4 bonds of lignin model compounds at a low oxygen pressure. Under the optimized reaction conditions, the conversion of 2-(2-methoxyphenoxy)-1-phenylethanol up to 95% with high selectivities was achieved with a variety of substrates investigated. The reusability of the Co catalyst with a high catalytic efficiency indicates its potential application in the oxidative cleavage of C–O bonds.

Amides are ubiquitous molecules in nature and in synthetic chemistry. Here we report a convenient and efficient method to synthesize N-aryl amides via amidation of esters with nitroarenes. In the presence of manganese metal, this amidation proceeded smoothly without the need for additional catalysts or ligands. Various esters and nitroarenes are suitable substrates to afford a wide range of N-aryl amides, including bio-active molecules and intermediates to drug molecules.

Chiral alkyl amines are omnipresent as bioactive molecules and synthetic intermediates. The catalytic and enantioselective synthesis of alkyl amines from readily accessible precursors is challenging. Here we develop a nickel-catalyzed hydroalkylation method to assemble a wide range of chiral alkyl amines from enecarbamates (N-Cbz-protected enamines) and alkyl halides with high regio- and enantioselectivity. The method works for both nonactivated and activated alkyl halides and is able to produce enantiomerically enriched amines with two minimally differentiated α-alkyl substituents. The mild conditions lead to high functional group tolerance, which is demonstrated in the postproduct functionalization of many natural products and drug molecules, as well as the synthesis of chiral building blocks and key intermediates to bioactive compounds.