Iron-substituted CoOOH porous nanosheet arrays grown on carbon fiber cloth (denoted as Fe Co OOH PNSAs/CFC, 0≤x≤0.33) with 3D hierarchical structures are synthesized by in situ anodic oxidation of α-Co(OH) NSAs/CFC in solution of 0.01 m (NH ) Fe(SO ) . X-ray absorption fine spectra (XAFS) demonstrate that CoO octahedral structure in CoOOH can be partially substituted by FeO octahedrons during the transformation from α-Co(OH) to Fe Co OOH, and this is confirmed for the first time in this study. The content of Fe in Fe Co OOH, no more than 1/3 of Co, can be controlled by adjusting the in situ anodic oxidation time. Fe Co OOH PNSAs/CFC shows superior OER electrocatalytic performance, with a low overpotential of 266 mV at 10 mA cm , small Tafel slope of 30 mV dec , and high durability.

The study of cost-efficient and high-performance electrocatalysts for oxygen evolution reaction (OER) has attracted much attention. Here, porous microrod arrays constructed by carbon-confined NiCo@NiCoO core@shell nanoparticles (NiCo@NiCoO /C PMRAs) are fabricated by the reductive carbonization of bimetallic (Ni, Co) metal-organic framework microrod arrays (denoted as NiCo-MOF MRAs) and subsequent controlled oxidative calcination. They successfully combine the desired merits including large specific surface areas, high conductivity, and multiple electrocatalytic active sites for OER. In addition, the oxygen vacancies in NiCo@NiCoO /C PMRAs significantly improve the conductivity of NiCoO and accelerate the kinetics of OER. The above advantages obviously enhance the electrocatalytic performance of NiCo@NiCoO /C PMRAs. The experimental results demonstrate that the NiCo@NiCoO /C PMRAs as electrocatalysts exhibit high catalytic activity, low overpotential, and high stability for OER in alkaline media. The strategy reported will open up a new route for the fabrication of porous bimetallic composite electrocatalysts derived from MOFs with controllable morphology for electrochemical energy conversion devices.

Electrocatalytic water splitting is considered as a promising route to use renewable energy for hydrogen production; however, its industrial application is limited by the anodic reaction, oxygen evolution reaction (OER). The key solution to unleash this constrain is to find an electrocatalyst that reduces the overpotential (η) of OER. Among the various electrocatalysts, perovskites have attracted intense attention recently for their high OER performance and low cost. To realize the commercial potential of perovskites, understanding its surface chemistry, including leaching, reconstruction, and lattice oxygen participated OER, is crucial to develop the nextgeneration perovskite catalysts,. In this Review, the perovskite surface stability is emphasized to be closely related to the chemical component of perovskite surface, which can be well controlled by surface engineering and further improves its OER performance. A new descriptor (stability level) is proposed to highlight the relationship between OER performance and surface stability of perovskite. This descriptor will provide potential strategies to optimize OER catalytic performance by tuning surface structure of perovskite.

In the process of oxygen evolution reaction (OER) on perovskite, it is of great significance to accelerate the hindered lattice oxygen oxidation process to promote the slow kinetics of water oxidation. In this paper, a facile surface modification strategy of nanometer-scale iron oxyhydroxide (FeOOH) clusters depositing on the surface of LaNiO3 (LNO) perovskite is reported, and it can obviously promote hydroxyl adsorption and weaken Ni-O bond of LNO. The above relevant evidences are well demonstrated by the experimental results and DFT calculations. The excellent hydroxyl adsorption ability of FeOOH-LaNiO3 (Fe-LNO) can obviously optimize OH- filling barriers to promote lattice oxygen-participated OER (LOER), and the weakened Ni-O bond of LNO perovskite can obviously reduce the reaction barrier of the lattice oxygen participation mechanism (LOM). Based on the above synergistic catalysis effect, the Fe-LNO catalyst exhibits a maximum factor of 5 catalytic activity increases for OER relative to the pristine perovskite and demonstrates the fast reaction kinetics (low Tafel slope of 42 mV dec-1) and superior intrinsic activity (TOFs of ~40 O2 S-1 at 1.60 V vs. RHE).

The instinct activity of NiFe layer double hydroxides (LDHs) for oxygen evolution reaction (OER) suffers from its predominately exposed basal plane (003), which was thought to be poor-activity. Herein, we...

High-entropy alloy (HEA) nanoparticles are promising catalyst candidates for the acidic oxygen evolution reaction (OER). Herein, we report the synthesis of IrFeCoNiCu-HEA nanoparticles on a carbon paper substrate via a microwaveassisted shock synthesis method. Under OER conditions in 0.1 M HClO 4 , the HEA nanoparticles exhibit excellent activity with an overpotential of ∼302 mV measured at 10 mA cm −2 and improved stability over 12 h of operation compared to the monometallic Ir counterpart. Importantly, an active Ir-rich shell layer with nanodomain features was observed to form on the surface of IrFeCoNiCu-HEA nanoparticles immediately after undergoing electrochemical activation, mainly due to the dissolution of the constituent 3d metals. The core of the particles was able to preserve the characteristic homogeneous single-phase HEA structure without significant phase separation or elemental segregation. This work illustrates that under acidic operating conditions, the near-surface structure of HEA nanoparticles is susceptible to a certain degree of structural dynamics.

Hydrogen-derived power is one of the most promising components of a fossil fuel-independent future when deployed with green and renewable primary energy sources. Energy from the sun, wind, waves/tidal, and other emissions-free sources can power water electrolyzers (WEs), devices that can produce green hydrogen without carbon emissions. According to recent International Renewable Energy Agency reports, most WEs employed in the industry are currently alkaline water electrolyzers and proton-exchange membrane water electrolyzers (PEMWEs), with ∼200 and ∼70 years of commercialization history, respectively. The former suffers from inherently limited current densities due to inevitable gas crossover, operates using corrosive (7 M) alkaline solutions, and requires large installation footprints, while the latter requires expensive and scarce precious metal-based electrocatalysts. An emerging technology, the anion-exchange membrane water electrolyzer (AEMWE), seeks to combine the benefits of both into one device while overcoming the limitations of each. AEMWEs afford higher operating current densities and pressures, similar Faradaic efficiencies when compared to PEMWEs (>90%), rapid ramping/load-following responsiveness, and the use of non-noble metal catalysts and pure water feed. While recent reports show promising device performance, close to 3 A/cm 2 for AEMWEs with 1 M KOH or pure water feed, a deeper understanding of the mechanisms that govern device performance and stability is required for the technology to compete and flourish. Herein, we briefly discuss the fundamentals of AEMWEs in terms of device components, catalysts, membranes, and long-term stability/durability. We provide our perspective on where the field is going and offer our opinion on how specific performance and stability tests should be performed to facilitate the development of the field.

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