Tuning Interfacial Electron Transfer by Anchoring NiFe-LDH on In-situ Grown Cu2O for Enhancing Oxygen Evolution

Modulating Intrinsic Sulfate Ions in FeOOH Nanorods for Enhanced Energy Storage and Catalytic Oxygen Evolution

Designing efficient low-cost earth-abundant metal electrodes for enhanced energy storage and sluggish oxygen evolution reactions (OERs) poses significant challenges in electrochemistry. Herein an innovative approach to boost the activity of FeOOH nanorods for energy storage and catalytic OER by initiating intrinsic sulfate ion (SO4 2-) modulation is proposed. Through a one-step hydrothermal synthesis using a polymeric ferric sulfate precursor, it is successfully cultivated sulfated iron oxyhydroxide (S-FeOOH) nanorods. Remarkably, the presence of sulfate ions effectively prevented the transformation of FeOOH into less active Fe2O3, even under elevated temperature. Annealing induced the leaching of sulfate ions, leading to structural rearrangements with shorter Fe-O bond lengths and the formation of sulfate-textured FeOOH (ST-FeOOH) with additional active sites, consequently increasing the material's surface area. Importantly, compared with reported non-noble metal catalysts, the ST-FeOOH nanorods exhibited significantly enhanced energy storage capabilities (3684 mF cm-2) and catalytic performance in the OER. With a low overpotential of 173 mV to achieve a current density of 10 mA cm-2, fast OER kinetics (39 mV dec-1), and exceptional stability exceeding 80 h, these nanorods demonstrate their potential as efficient OER catalysts. This work demonstrates sulfate ion modulation's role in tailoring FeOOH nanorods for advanced cost-effective electrodes and OER electrocatalysts.

Recent Progress in the Design and Application of Strong Metal-Support Interactions in Electrocatalysis

The strong metal-support interaction (SMSI) in supported metal catalysts represents a crucial factor in the design of highly efficient heterogeneous catalysts. This interaction can modify the surface adsorption state, electronic structure, and coordination environment of the supported metal, altering the interface structure of the catalyst. These changes serve to enhance the catalyst's activity, stability, and reaction selectivity. In recent years, a multitude of researchers have uncovered a range of novel SMSI types and induction methods including oxidized SMSI (O-SMSI), adsorbent-mediated SMSI (A-SMSI), and wet chemically induced SMSI (Wc-SMSI). Consequently, a systematic and critical review is highly desirable to illuminate the latest advancements in SMSI and to deliberate its application within heterogeneous catalysts. This article provides a review of the characteristics of various SMSI types and the most recent induction methods. It is concluded that SMSI significantly contributes to enhancing catalyst stability, altering reaction selectivity, and increasing catalytic activity. Furthermore, this paper offers a comprehensive review of the extensive application of SMSI in the electrocatalysis of hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and carbon dioxide reduction reaction (CO2RR). Finally, the opportunities and challenges that SMSI faces in the future are discussed.

Electrocatalytic Upcycling of Nitrate Wastewater into an Ammonia Fertilizer via an Electrified Membrane

Electrochemically upcycling wastewater nitrogen such as nitrate (NO₃^-) and nitrite (NO₂^-) into an ammonia fertilizer is a promising yet challenging research topic in resource recovery and wastewater treatment. This study presents an electrified membrane made of a CuO@Cu foam and a polytetrafluoroethylene (PTFE) membrane for reducing NO₃^- to ammonia (NH₃) and upcycling NH₃ into (NH₄)₂SO₄, a liquid fertilizer for ready-use. A paired electrolysis process without external acid/base consumption was achieved under a partial current density of 63.8 ± 4.4 mA·cm^-2 on the cathodic membrane, which removed 99.9% NO₃^- in the feed (150 mM NO₃^-) after a 5 h operation with an NH₃ recovery rate of 99.5%. A recovery rate and energy consumption of 3100 ± 91 g-(NH₄)₂SO₄·m^-2·d^-1 and 21.8 ± 3.8 kWh·kg^-1-(NH₄)₂SO₄, respectively, almost outcompete the industrial ammonia production cost in the Haber-Bosch process. Density functional theory (DFT) calculations unraveled that the in situ electrochemical conversion of Cu²⁺ into Cu¹⁺ provides highly dynamic active species for NO₃^- reduction to NH₃. This electrified membrane process was demonstrated to achieve synergistic nitrate decontamination and nutrient recovery with durable catalytic activity and stability.

NiFeMn-Layered Double Hydroxides Linked by Graphene as High-Performance Electrocatalysts for Oxygen Evolution Reaction

Currently, precious metal group materials are known as the efficient and widely used oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts. The exorbitant prices and scarcity of the precious metals have stimulated scale exploration of alternative non-precious metal catalysts with low-cost and high performance. Layered double hydroxides (LDHs) are a promising precursor to prepare cost-effective and high-performance catalysts because they possess abundant micropores and nitrogen self-doping after pyrolysis, which can accelerate the electron transfer and serve as active sites for efficient OER. Herein, we developed a new highly active NiFeMn-layered double hydroxide (NFM LDH) based electrocatalyst for OER. Through building NFM hydroxide/oxyhydroxide heterojunction and incorporation of conductive graphene, the prepared NFM LDH-based electrocatalyst delivers a low overpotential of 338 mV at current density of 10 mA cm⁻² with a small Tafel slope of 67 mV dec⁻¹, which are superior to those of commercial RuO₂ catalyst for OER. The LDH/OOH heterojunction involves strong interfacial coupling, which modulates the local electronic environment and boosts the kinetics of charge transfer. In addition, the high valence Fe³⁺ and Mn³⁺ species formed after NaOH treatment provide more active sites and promote the Ni²⁺ to higher oxidation states during the O₂ evolution. Moreover, graphene contributes a lot to the reduction of charge transfer resistance. The combining effects have greatly enhanced the catalytic ability for OER, demonstrating that the synthesized NFM LDH/OOH heterojunction with graphene linkage can be practically applied as a high-performance electrocatalyst for oxygen production via water splitting.

Introducing Oxygen Vacancies to NiFe LDH through Electrochemistry Reduction to Promote Oxygen Evolution Reaction

The transition metal hydroxide NiFe LDH is a promising oxygen evolution reaction (OER) catalyst. Surface engineering, such as the introduction of oxygen vacancies into NiFe LDH, has been reported to...