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Developing high‐performance, low‐loading, Ir‐based electrocatalysts for the oxygen evolution reaction (OER) in acidic media is still a great challenge. Herein, we fabricated an iridium manganese catalyst with only 5 % iridium. The influence of the manganese dioxide phase states (α‐, β‐, γ‐ and δ‐MnO2) on the OER performance of IrO2/MnO2 catalysts was investigated. α‐MnO2, as the substrate, can generate smaller iridium particles and more high‐valence‐state iridium to promote OER performance. Therefore, the 5 % IrO2/α‐MnO2 electrocatalyst exhibits excellent electrocatalytic OER performance with a high mass activity of 216.67 A/gIr and 655.33 A/gIr at 1.53 V in acidic and alkaline media, respectively, significantly outperforming commercial IrO2. [ABSTRACT FROM AUTHOR]

• Stepped cuprous oxide with abundant Cu vacancies was developed. • High C 2 H 4 partial current density and production rate are achieved. • Cu vacancies tune the electronic structure and enhance the electrochemical activity. • DFT calculations reveal that Cu vacancy facilitates the adsorption of *COH and weakens the binding of *CO and *CH 2. Electrochemical carbon dioxide (CO 2) reduction powered by renewable energy source is a promising strategy for the sustainable carbon cycle, while the selectivity toward C 2+ products is still a great challenge. Herein, a novel stepped cuprous oxide catalyst with abundant Cu vacancies (Cu v -Cu 2 O catalyst) is developed to enhance the selectivity and efficiency of CO 2 conversion toward C 2 products. This catalyst exhibits high C 2 H 4 partial current density and production rate at a low overpotential benefiting from the stepped surface and the modified electronic structure by Cu vacancies. Furthermore, density functional theory calculations demonstrate that the Cu vacancy-enriched Cu 2 O surface ensures strong adsorption to *COH but weak affinities to *CO and *CH 2 intermediates, which promotes CO 2 electroreduction to C 2 H 4 products. The enhanced selectivity of C 2 H 4 , accompanied with the Cu vacancies and Cu+ species, can remain stable during the long-term test. This study will provide guidance on designing efficient electrocatalysts for CO 2 reduction towards hydrocarbon products. [ABSTRACT FROM AUTHOR]

• Dendritic In-doped Cu@Cu 2 O catalyst is prepared by co-electrodeposition method. • Doped-In content can tailor Cu+/Cu0 ratio, charge distribution, morphology and ECSA. • Cu+/Cu0 ratio plays a vital role on enhancing FE CO and partial current density at low In doping. • 3.7% In-Cu sample shows the highest FE CO of 87.6 ± 2.2 % and j CO of 9.7 ± 1.04 mA cm -2. Element doping is an effective strategy to enhance the selectivity of electrochemical carbon dioxide reduction. In this work, a dendritic core-shell In-doped Cu@Cu 2 O catalyst is prepared by co-electrodeposition method on carbon fiber paper for selective electroreduction of CO 2 to CO. Faradaic efficiency of producing CO over this dendritic In-doped Cu@Cu 2 O reaches 87.6 ± 2.2% with total current density of 11.1 ± 0.85 mA cm−2 at −0.8 V vs RHE, which outperforms most of the reported Cu-based electrocatalysts. The excellent performance is mainly derived from charge re-distribution and the enhanced intrinsic activity due to the formation of In-doped Cu 2 O layer. Meanwhile, the Cu+/Cu0 can be adjusted by tailoring the doped-In content. The relatively high ECSA and small charge transfer resistance are also conducive to improve the selectivity and activity. The oxyphilic In metal incorporated into the copper lattice can well stabilize the intermediate *COOH through enhancing interaction with O-ends of *COOH. This work provides a facile approach and a deep insight on design and synthesis of high efficiency hybrid electrocatalysts. [ABSTRACT FROM AUTHOR]

As a new class of metal–nitrogen–carbon (M−N−C) material with 3 D microstructure, zeolitic imidazolate frameworks (ZIFs) are used to synthesize highly active electrocatalysts for the oxygen reduction reaction, as substitutes for commercial Pt/C in anion exchange membrane fuel cells. However, to form an effective catalyst layer (CL), the relationship between the microstructure of the ZIF‐derived catalyst and the fuel cell performance must be investigated. In this work, a hierarchically porous CL based on the carbon black (CB)‐controlled synthesis of a Co‐based ZIF (denoted as ZIF‐CB‐700) is constructed to optimize the triple‐phase boundary (TPB) and mass transfer. The power density at 40 °C of ZIF‐CB‐700 (95.4 mW cm−2) as cathode catalyst is about 4 times higher than that of the catalyst synthesized in the absence of CB and is comparable to that of the commercial 60 % Pt/C catalyst (112.0 mW cm−2). Both online and offline measurements suggest that the morphology and microstructure of the CL is crucial to form an active TPB region, dominating the fuel cell performance rather than only the high catalyst activity. [ABSTRACT FROM AUTHOR]

Developing efficient electrocatalysts from the earth‐abundant transition‐metal family is a great challenge for overall water splitting. Herein, we developed an approach to regulate the morphology and electronic structure of α‐Co0.9Fe0.1(OH)x nanoplates, in which FeCl2 (as a precursor) plays a significant role under reflux conditions. The resulting 2D α‐Co0.9Fe0.1(OH)x nanoplates exhibit more accessible edge active sites and more high‐valence Co species to boost its intrinsic activity. Therefore, this electrocatalyst shows outstanding oxygen evolution reaction performance (with an overpotential of 225 mV at 10 mA cm−2 and a Tafel slope of 39 mV dec−1 and good stability) and excellent activity toward the hydrogen evolution reaction (with an overpotential of 122 mV at 10 mA cm−2) in 1M KOH solution. When employed as bifunctional electrocatalysts on both the anode and cathode for overall water splitting, α‐Co0.9Fe0.1(OH)x can afford 10 mA cm−2 at 1.62 V with long‐term stability. The one‐pot synthesis of 2D Fe‐doped transition‐metal hydroxide nanoplates enriched with abundant edge sites may provide a new strategy for fabricating efficient overall water splitting catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Direct methanol fuel cells are promising renewable energy devices for automobiles and portable electronic devices. The development of high effciency, poison tolerance, long‐term stability, and noble metal‐free electrocatalysts for methanol oxidation is still a major challenge. Herein, we develop a noble metal‐free, 3D self‐supported, defect‐rich, hierarchical shell‐core structured Ni3S2 composite on Ni foam as electrocatalyst. This electrocatalyst shows a good activity, poison tolerance, and long‐term durability towards methanol oxidation in alkaline media. It shows the lowest onset potential (−340 mV vs. Hg/HgO) among all the Ni‐based catalysts reported up to date and a Pt‐level specific activity. The methanol oxidation peak current of the electrocatalyst retains more than 97.5 % even after 5,000 voltammetry cycles in 0.5 M KOH+1 M CH3OH. The morphology and composition of the electrocatalysts before and after stability test were characterized by SEM, TEM, XRD, and XPS. The high activity, poison tolerance, and stability are attributed to the binder‐free, directly grown Ni3S2 shell on the Ni foam backbone, the lattice defect sites, and the synergetic effects between the in‐situ formed active NiOx core and Ni3S2 shell during methanol oxidation. This work indicates that the self‐supported hierarchical shell‐core Ni3S2@Ni foam electrocatalyst is a viable alternative for commercial Pt‐based electrocatalyst applied in fuel cells. [ABSTRACT FROM AUTHOR]

Identification of active sites for oxygen evolution reaction (OER) plays a key role in the design and fabrication of high-performance cobalt-based electrocatalysts. Herein, we report the synthesis of two types of two-dimensional monometallic cobalt hydroxide nanoplates in aqueous solution for OER: α-Co(OH)2 with both Co2+Td and Co2+Oh sites and β-Co(OH)2 with Co2+Oh sites. Electrochemical characterization reveals that α-Co(OH)2 is more active than β-Co(OH)2 towards OER. The better activity can be attributed to the presence of Co2+Td sites in α-Co(OH)2, which are more active than Co2+Oh sites. Our finding clarifies the contribution of the two catalytic sites and helps future rational design of high-performance OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Finding cost-effective, active and durable catalyst materials for energy applications, such as electrocatalytic hydrogen production, is an intriguing challenge. Here, a facile and effective approach to the design and construction of two-dimensional MoS 2 and WS 2 interleaved nanowalls with maximum exposures of active edges on silk-derived N-doped carbon fibers (SNCF) was demonstrated. The morphological evolutions of the MoS 2 and WS 2 nanocrystals on the SNCF from crescent-like nanosheets to an interleaved nanowall network can be obtained by adjusting the concentrations of the Mo and W precursors. These robust MoS 2 /SNCF and WS 2 /SNCF electrocatalysts exhibit prominent hydrogen evolution reaction (HER) activities with onset potentials of −40 and −96 mV and Tafel slopes of 60 and 66 mV dec −1 , respectively. The overpotentials ( η ) at j = −10 mA cm −2 for MoS 2 /SNCF and WS 2 /SNCF are −102 and −157 mV, respectively. In addition, MoS 2 /SNCF and WS 2 /SNCF are both able to sustain continuous HER operation for 10 h under working conditions with only a slight degradation in current densities, implying excellent durability and a prospect for practical applications. [ABSTRACT FROM AUTHOR]

The copper-based catalyst is considered to be the only catalyst for electrochemical carbon dioxide reduction to produce a variety of hydrocarbons, but its low selectivity and low current density to C2 products restrict its development. Herein, a core-shell xZnO@yCu2O catalysts for electrochemical CO2 reduction was fabricated via a two-step route. The high selectivity of C2 products of 49.8% on ZnO@4Cu2O (ethylene 33.5%, ethanol 16.3%) with an excellent total current density of 140.1 mA cm−2 was achieved over this core-shell structure catalyst in a flow cell, in which the C2 selectivity was twice that of Cu2O. The high electrochemical activity for ECR to C2 products was attributed to the synergetic effects of the ZnO core and Cu2O shell, which not only enhanced the selectivity of the coordinating electron, improved the HER overpotential, and fastened the electron transfer, but also promoted the multielectron involved kinetics for ethylene and ethanol production. This work provides some new insights into the design of highly efficient Cu-based electrocatalysts for enhancing the selectivity of electrochemical CO2 reduction to produce high-value C2 products. [ABSTRACT FROM AUTHOR]

Abstract We report a CeO 2 incorporated cobalt oxide electrode with abundant nano-sized interfaces. The as-prepared heterostructures exhibit remarkable oxygen evolution reaction (OER) activity and excellent stability, surpassing the pristine cobalt oxide and the state-of-art RuO 2. Further DFT calculations and experimental results indicate that the improved OER performance of CoO-CeO 2 heterostructures originates from the hierarchically porous structure, large surface area and high electron density around Co sites. The armouphous phase is formed during OER test due to surface Ce leaching, which can further promoted the performance of the hybrids. This work elucidates the cooperative effects and in situ transformation of CeO 2 -incorporated cobalt oxide in water oxidation, providing a valuable guideline for designing electrocatalysts. Highlights • The CoO-CeO 2 heterostructures are prepared via a self-assembling method. • The hybrids feature abundant interfaces and hierarchically porous structure. • The hybrids show excellent OER activity and long-term stability. • The enhancement is due to large surface area and strong electronic interaction. • The in situ formed amorphous phase can further improve OER performance. [ABSTRACT FROM AUTHOR]

• A novel electrodeposition method is developed to prepare self-supported amorphous IrO x /Ti electrode. • Pre-activation plays a significant role in in-situ constructing an amorphous film. • The amorphous IrO x film exposes high contents of active IrIII species and surface hydroxides to enhance the OER performance. • Amorphous-crystalline synergy and rich interface contribute to the superior stability and activity. • A super durability for 190 h at 10 mA cm−2 and 50 mA cm−2 was achieved for amorphous IrO x -50/Ti. Developing highly active and stable electrocatalysts for acidic oxygen evolution reaction is still a great challenge. Herein, we developed a novel self-supported amorphous IrO x catalyst (IrO x /Ti) encapsulated with a small number of crystalline nanoparticles for efficient acidic OER. The resulting IrO x -50-AC/Ti electrode exhibits a superior OER performance with an overpotential of 250 mV at 10 mA cm−2 and Tafel slope of 50.4 mV dec−1 in 0.1 M HClO 4. High contents of IrIII species and surface hydroxide groups, hierarchically porous structure and high defective density contribute to boost the OER activity. Importantly, the amorphous IrO x -50-AC/Ti also demonstrates a super long-term durability for 190 h due to the strong interaction between IrO x film and Ti. The unique amorphous-crystalline structure also enhances the stability and the activity by promoting the synergy between amorphous phase and crystalline phase. This work provides some valuable insights on developing efficient Ir-based catalysts for acidic water splitting. [Display omitted] A novel self-supported amorphous IrO x catalyst (IrO x /Ti) is developed by an electrodeposition strategy for efficient acidic OER. The optimized amorphous IrO x -50-AC/Ti demonstrates a super long-term durability for 190 h and an excellent activity with an overpotential of 250 mV to obtain 10 mA cm−2 in 0.1 M HClO 4. [ABSTRACT FROM AUTHOR]

To develop robust and highly active bifunctional electrocatalysts for electrochemical water splitting in acidic media is still a great challenge for proton exchange membrane (PEM) electrolyzer. Herein, a self-assembled IrCo x nanorings (NRs) with bracelet-like architecture is fabricated as a bifunctional high-efficient overall water splitting electrocatalyst by a facile, controllable and surfactant-free strategy. The unique nanoring architecture enriches in abundant homointerface and strong synergistic electronic interaction between Ir and Co. The optimized IrCo 0.14 NRs exhibits remarkable electrocatalytic performance with a low overpotential of 16 mV for hydrogen evolution reaction (HER) and 278 mV for oxygen evolution reaction (OER) at 10 mA cm−2 in 0.1 M HClO 4 , respectively, significantly outperforming the commercial Pt/C, Ir/C and reported Ir-based catalysts. As both anode and cathode, a cell voltage of only 1.53 V to reach 10 mA cm−2 is obtained for overall water splitting and no obvious activity loses after a long-term electrolysis for 14 h. Combined with a PV cell, this catalyst also shows excellent water splitting performance with a solar-to-hydrogen conversion efficiency of 12.8%. This work provides further insights on designing promising and efficient bifunctional electrocatalysts for clean energy electrochemical conversion in the future. Image 1 • Bracelet-like IrCo x nanorings (NRs) assembled by alloy nanoparticles are fabricated. • The homointerface and alloy effects of IrCo x NRs boost the catalytic performance. • IrCo 0.14 NR catalyst exhibits superior HER and OER performance in acidic media. • IrCo 0.14 NR enables stable water splitting in acidic media for 14 h at 10 mA cm−2. • IrCo 0.14 NR also exhibits excellent solar-driven overall water splitting performance. [ABSTRACT FROM AUTHOR]