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Metal–organic frameworks (MOFs) are increasingly being investigated as electrocatalysts for the oxygen evolution reaction (OER). Despite their promising catalytic activity, many fundamental questions concerning their structure−performance relationships—especially those regarding the roles of active species—remain to be answered. Here we show the structural transformation of a Ni 0.5 Co 0.5 -MOF-74 during the OER by operando X-ray absorption spectroscopy analysis and high-resolution transmission electron microscopy imaging. We suggest that Ni 0.5 Co 0.5 OOH 0.75 , with abundant oxygen vacancies and high oxidation states, forms in situ and is responsible for the high OER activity observed. The ratio of Ni to Co in the bimetallic centres alters the geometric and electronic structure of as-formed active species and in turn the catalytic activity. Based on our understanding of this system, we fabricate a Ni 0.9 Fe 0.1 -MOF that delivers low overpotentials of 198 mV and 231 mV at 10 mA cm −2 and 20 mA cm −2 , respectively. Metal–organic frameworks (MOFs) are increasingly being explored for electrocatalytic oxygen evolution, which is half of the water splitting reaction. Here the authors show that, under reaction conditions, mixed metal oxyhydroxides form at the nodes of bimetallic MOFs, which are highly catalytically active.

Atomic-level coordination engineering is an efficient strategy for tuning the catalytic performance of single-atom catalysts (SACs). However, their rational design has so far been plagued by the lack of a universal correlation between the coordination symmetry and catalytic properties. Herein, we synthesised planar-symmetry-broken CuN 3 (PSB-CuN 3 ) SACs through microwave heating for electrocatalytic CO 2 reduction. Remarkably, the as-prepared catalysts exhibited a selectivity of 94.3% towards formate at −0.73 V vs. RHE, surpassing the symmetrical CuN 4 catalyst (72.4% at −0.93 V vs. RHE). In a flow cell equipped with a PSB-CuN 3 electrode, over 90% formate selectivity was maintained at an average current density of 94.4 mA cm −2 during 100 h operation. By combining definitive structural identification with operando X-ray spectroscopy and theoretical calculations, we revealed that the intrinsic local symmetry breaking from planar D 4 h configuration induces an unconventional dsp hybridisation, and thus a strong correlation between the catalytic activity and microenvironment of metal centre (i.e., coordination number and distortion), with high preference for formate production in CuN 3 moiety. The finding opens an avenue for designing efficient SACs with specific local symmetries for selective electrocatalysis. Atomic-level coordination influences the properties of single-atom-catalysts but is difficult to precisely engineer. Here, authors study the role of local symmetry manipulation, finding planar-symmetry-broken CuN 3 catalysts outperform highly symmetrical CuN 4 for CO 2 electroreduction to formic acid.

The chlor-alkali process plays an essential and irreplaceable role in the modern chemical industry due to the wide-ranging applications of chlorine gas. However, the large overpotential and low selectivity of current chlorine evolution reaction (CER) electrocatalysts result in significant energy consumption during chlorine production. Herein, we report a highly active oxygen-coordinated ruthenium single-atom catalyst for the electrosynthesis of chlorine in seawater-like solutions. As a result, the as-prepared single-atom catalyst with Ru-O 4 moiety (Ru-O 4 SAM) exhibits an overpotential of only ~30 mV to achieve a current density of 10 mA cm −2 in an acidic medium (pH = 1) containing 1 M NaCl. Impressively, the flow cell equipped with Ru-O 4 SAM electrode displays excellent stability and Cl 2 selectivity over 1000 h continuous electrocatalysis at a high current density of 1000 mA cm −2 . Operando characterizations and computational analysis reveal that compared with the benchmark RuO 2 electrode, chloride ions preferentially adsorb directly onto the surface of Ru atoms on Ru-O 4 SAM, thereby leading to a reduction in Gibbs free-energy barrier and an improvement in Cl 2 selectivity during CER. This finding not only offers fundamental insights into the mechanisms of electrocatalysis but also provides a promising avenue for the electrochemical synthesis of chlorine from seawater electrocatalysis. Chlor-alkali process plays an important role in the chemical industry. However, large overpotential and low selectivity of currently used catalysts lead to high energy consumption. Here the authors report Ru-O 4 single site catalysts for chlorination evolution with 1000 h stability at 1000 mA cm −2 in a seawater-like environment.

Electrocatalysis is at the heart of many significant chemical transformation processes and advanced clean energy technologies. Traditional noble/transition metal oxides are widely used as electrocatalysts; however, they often suffer from intrinsic disadvantages, including low atom utilization, small surface area, and unfavorable tunability. Metal–organic frameworks (MOFs), as a new family of catalytic materials, are attracting extensive attention due to their unique physicochemical properties. The tremendous pristine MOF‐based materials are created using various synthetic approaches and further used for important energy conversions. Herein, a systematic overview on the unique merits and the state‐of‐the‐art design of MOF‐based electrocatalysts is offered. This review also presents recent advances in the development of various pristine MOFs and MOF‐based host–guest composite catalysts for electrocatalysis (i.e., oxygen reduction reaction, hydrogen oxidation reaction, hydrogen evolution reaction, oxygen evolution reaction, and CO2 reduction reaction) and discusses the future challenges and opportunities in this emerging field. Metal–organic frameworks (MOFs) are a new family of catalytic materials, holding great promise in many energy‐conversion processes due to their unique physicochemical properties. This review systematically outlines the distinctive superiorities and state‐of‐the‐art development of MOF‐based catalysts. A critical summary is provided on their recent advances in electrocatalysis. Future key challenges and opportunities are suggested.

Metal-free electrocatalysts represent a main branch of active materials for oxygen evolution reaction (OER), but they excessively rely on functionalized conjugated carbon materials, which substantially restricts the screening of potential efficient carbonaceous electrocatalysts. Herein, we demonstrate that a mesostructured polyacrylate hydrogel can afford an unexpected and exceptional OER activity – on par with that of benchmark IrO 2 catalyst in alkaline electrolyte, together with a high durability and good adaptability in various pH environments. Combined theoretical and electrokinetic studies reveal that the positively charged carbon atoms within the carboxylate units are intrinsically active toward OER, and spectroscopic operando characterizations also identify the fingerprint superoxide intermediate generated on the polymeric hydrogel backbone. This work expands the scope of metal-free materials for OER by providing a new class of polymeric hydrogel electrocatalysts with huge extension potentials. Hydrogels are networked hydrophilic polymers with enriched polar groups and confined water but are relatively less explored as electrocatalysts. Here, the authors demonstrate that insulative polymeric hydrogels can be an underlying catalogue of metal-free oxygen evolution electrocatalyst with huge extension potentials.

Atomically precise gold (Au) nanoclusters (NCs) as visible light photosensitizers supported on the substrate for photoredox catalysis have attracted considerable attentions. However, efficient control of their photocatalytic activity and long-term stability is still challenging. Herein, we report a coordination-assisted self-assembly strategy in combination with electrostatic interaction to sandwich Au 25 (Capt) 18 (abbreviated as Au 25 , Capt = captopril) NCs between an inner core and an outer shell made of UiO-66, denoted as UiO-66@Au 25 @UiO-66. Notably, the sandwich-like nanocomposite displays significantly enhanced catalytic activity along with an excellent stability when used in the selective photocatalytic aerobic oxidation of sulfide to sulfoxide. As comparison, Au 25 NCs simply located at the outer surface or insider matrix of UiO-66 (short as Au 25 /UiO-66 and Au 25 @UiO-66) show poor stability and low conversion, respectively. This structure regulated difference in the catalytic performances of three nanocomposites is assigned to the varied distribution of active sites (Au NCs) in metal-organic frameworks (MOFs). This work offers the opportunity for application of nanoclusters in catalysis, energy conversion and even biology.

Photoelectrochemical water splitting has long been considered an ideal approach to producing green hydrogen by utilizing solar energy. However, the limited photocurrents and large overpotentials of the anodes seriously impede large-scale application of this technology. Here, we use an interfacial engineering strategy to construct a nanostructural photoelectrochemical catalyst by incorporating a semiconductor CdS/CdSe-MoS 2 and NiFe layered double hydroxide for the oxygen evolution reaction. Impressively, the as-prepared photoelectrode requires an low potential of 1.001 V vs. reversible hydrogen electrode for a photocurrent density of 10 mA cm −2 , and this is 228 mV lower than the theoretical water splitting potential (1.229 vs. reversible hydrogen electrode). Additionally, the generated current density (15 mA cm −2 ) of the photoelectrode at a given overpotential of 0.2 V remains at 95% after long-term testing (100 h). Operando X-ray absorption spectroscopy revealed that the formation of highly oxidized Ni species under illumination provides large photocurrent gains. This finding opens an avenue for designing high-efficiency photoelectrochemical catalysts for successive water splitting. The limited photocurrents and large overpotentials impede practical application of photoelectrochemical water splitting. Here, the authors construct a CdS-CdSe/MoS2/NiFe layered double hydroxides photoanode, delivering a low potential and large photocurrent gains due to the formation of highly oxidized Ni species under illumination

The design and synthesis of efficient electrocatalysts are important for electrochemical conversion technologies. The oxygen evolution reaction (OER) is a key process in such conversions, having applications in water splitting and metal–air batteries. Here, we report ultrathin metal–organic frameworks (MOFs) as promising electrocatalysts for the OER in alkaline conditions. Our as-prepared ultrathin NiCo bimetal–organic framework nanosheets on glassy-carbon electrodes require an overpotential of 250 mV to achieve a current density of 10 mA cm −2 . When the MOF nanosheets are loaded on copper foam, this decreases to 189 mV. We propose that the surface atoms in the ultrathin MOF sheets are coordinatively unsaturated—that is, they have open sites for adsorption—as evidenced by a suite of measurements, including X-ray spectroscopy and density-functional theory calculations. The findings suggest that the coordinatively unsaturated metal atoms are the dominating active centres and the coupling effect between Ni and Co metals is crucial for tuning the electrocatalytic activity. Efficient electrocatalysts for the oxygen–evolution reaction are desired due to their importance in applications such as water splitting and metal–air batteries. Here, the authors engineer ultrathin metal–organic frameworks that require low overpotential to generate oxygen from alkaline media.

The development of stable and efficient low‐cost electrocatalysts is conducive to the industrialization of CO2. The synergy effect between the heterogeneous interface of metal/oxide can promote the conversion of CO2. In this work, Cu2O/ZnO heterostructures with partially reduced metal/oxide heterointerfaces in Zn plates (CZZ) have been synthesized for CO2 electroreduction in different cationic solutions (K+ and Cs+). Physical characterizations were used to demonstrate the heterojunction of Cu2O/ZnO and the heterointerfaces of metal/oxide; electrochemical tests were used to illustrate the enhancement of the selectivity of CO2 to CO in different cationic solutions. Faraday efficiency for CO with CZZ as catalyst reaches 70.9% in K+ solution (current density for CO −3.77 mA cm−2 and stability 24 h), and the Faraday efficiency for CO is 55.2% in Cs+ solution (−2.47 mA cm−2 and 21 h). In addition, in situ techniques are used to elucidate possible reaction mechanisms for the conversion of CO2 to CO in K+ and Cs+ solutions. Cu2O/ZnO heterostructure with partially reduced matal/oxide heterostructure in zinc plate (CZZ) is synthesized, and the effectiveness of CZZ as a CO2RR catalyst is verified, resulting in an improved catalyst performance with a CO selectivity of up to 70.9% at −0.95 V versus reversible hydrogen electrode, while maintaining a stability of 24 h.

In this study, we developed a novel confinement-synthesis approach to layered double hydroxide nanodots (LDH-NDs) anchored on carbon nanoparticles, which formed a three-dimensional (3D) interconnected network within a porous carbon support derived from pyrolysis of metal-organic frameworks (C-MOF). The resultant LDH-NDs@C-MOF nonprecious metal catalysts were demonstrated to exhibit super-high catalytic performance for oxygen evolution reaction (OER) with excellent operation stability and low overpotential (∼230 mV) at an exchange current density of 10 mAcm −2 . The observed overpotential for the LDH-NDs@C-MOF is much lower than that of large-sized LDH nanosheets (321 mV), pure carbonized MOF (411 mV), and even commercial RuO 2 (281 mV). X-ray absorption measurements and density functional theory (DFT) calculations revealed partial charge transfer from Fe 3+ through an O bridge to Ni 2+ at the edge of LDH-NDs supported by C-MOF to produce the optimal binding energies for OER intermediates. This, coupled with a large number of exposed active sides and efficient charge and electrolyte/reactant/product transports associated with the porous 3D C-MOF support, significantly boosted the OER performance of the LDH-ND catalyst with respect to its nanosheet counterpart. Apart from the fact that this is the first active side identification for LDH-ND OER catalysts, this work provides a general strategy to enhance activities of nanosheet catalysts by converting them into edge-rich nanodots to be supported by 3D porous carbon architectures.