Tuning Metal Elements in Open Frameworks for Efficient Oxygen Evolution and Oxygen Reduction Reaction Catalysts

Eccentric Corrosion-Induced Formation of γ-NiFeOOH and γ-NiCoOOH on NiFeCo Alloy for Enhanced OER

An indirect, swift, and easy method of enhancing the oxygen evolution reaction (OER) performance of an economically viable Fe-rich NiFeCo (NFC) alloy has been developed. This approach leverages the anodic potential sweeps applied indirectly to the counter electrode (CE) when one does cathodic hydrogen evolution reaction (HER) on by potential sweeping at the working electrode (WE). In this method, NFC was intentionally corroded indirectly by using it as a CE for the potential sweeping HER experiment done with a Pt WE. The indirectly corroded NFC (NFC_IC) featuring mostly γ-NiFeOOH and γ-NiCoOOH entities on the surface was able to begin the OER at an onset overpotential of 250 mV and reach the benchmark of 10 mA cm-2 at 290 mV, which is 60 and 55 mV lesser than that of the bare NFC and RuO2, respectively, all with exceptionally faster kinetics, as evidenced by a relatively smaller Tafel slope of 30 mV dec-1. These insights into designing a trimetallic alloy-based OER electrocatalyst have opened a previously unknown avenue in the development of advanced self-supported OER electrodes for better and efficient H2 production via water electrolysis.

Distinct Promotion of PEC Water Oxidation of Ta2O5/α-Fe2O3/Co-Ni PBA via Coupling Ni 3d with O 2p

The development of robust and effective photoanodes is crucial for photoelectrochemical hydrogen production via total water splitting. Herein, the Ta2O5/α-Fe2O3/Co-Ni PBA (TFPB-1) photoanode was constructed by the compositing n-type Ta2O5 and n-type α-Fe2O3 followed by the deposition of p-type Co-Ni PBA. The IPCE of TFPB-1 was increased to 35.4% compared to 13.9% for Ta2O5 owing to the significantly improved light absorption efficiency, carrier separation efficiency and injection efficiency. The TFPB-1 achieved a current density of 2.78 mA cm-2 at 1.23 V (vs RHE), which was around 18.5 times that of Ta2O5. The OER overpotential over TFPB-1 was reduced to 0.59 V compared to 1.13 V for Ta2O5, resulting in a substantial reduction in the free energy of PEC water oxidation over TFPB-1. As a result, TFPB-1 exhibited remarkably enhanced photoelectrocatalytic activity for oxygen evolution through water oxidation.

Perfect Is Perfect: Nickel Prussian Blue Analogue as A High-Efficiency Electrocatalyst for Hydrogen Peroxide Production

Prussian blue analogues (PBA) are a large family of functional materials with diverse applications such as in electrochemical fields. However, their use in the emerging two-electron oxygen reduction reaction for clean production of hydrogen peroxide (H2O2) is lagging. Herein, a general solvent exchange induced reconstruction strategy is demonstrated, through which an abnormal NiNi-PBA superstructure is synthesized as a high-performance electrocatalyst for H2O2 generation. The resultant NiNi-PBA superstructure has a stoichiometric composition with saturated lattice water, and a leaf-like morphology composed of interconnected small-size nanosheets with identical orientation and predominate {210} side surface exposure. Our studies show that the Ni-N centers on {210} facets are the active sites, and the saturated lattice H2O favors a six-coordinated environment that results in high selectivity. The "perfect" structure including stoichiometric composition and ideal facet exposure leads to a high selectivity of ~100 % and H2O2 yield of 5.7 mol g-1 h-1, superior to the reported MOF-based electrocatalysts and most other electrocatalysts.

Rational Design of Earth-Abundant Catalysts toward Sustainability

Catalysis is crucial for clean energy, green chemistry, and environmental remediation, but traditional methods rely on expensive and scarce precious metals. This review addresses this challenge by highlighting the promise of earth-abundant catalysts and the recent advancements in their rational design. Innovative strategies such as physics-inspired descriptors, high-throughput computational techniques, and artificial intelligence (AI)-assisted design with machine learning (ML) are explored, moving beyond time-consuming trial-and-error approaches. Additionally, biomimicry, inspired by efficient enzymes in nature, offers valuable insights. This review systematically analyses these design strategies, providing a roadmap for developing high-performance catalysts from abundant elements. Clean energy applications (water splitting, fuel cells, batteries) and green chemistry (ammonia synthesis, CO2 reduction) are targeted while delving into the fundamental principles, biomimetic approaches, and current challenges in this field. The way to a more sustainable future is paved by overcoming catalyst scarcity through rational design.

Regulating the Spin State Configuration in Bimetallic Phosphorus Trisulfides for Promoting Sulfur Redox Kinetics

Lithium-sulfur (Li-S) batteries suffer from sluggish kinetics due to the poor conductivity of sulfur cathodes and polysulfide shutting. Current studies on sulfur redox catalysis mainly focus on the adsorption and catalytic conversion of lithium polysulfides but ignore the modulation of the electronic structure of the catalysts which involves spin-related charge transfer and orbital interactions. In this work, bimetallic phosphorus trisulfides embedded in Prussian blue analogue-derived nitrogen-doped hollow carbon nanocubes (FeCoPS3/NCs) were elaborately synthesized as a host to reveal the relationship between the catalytic activity and the spin state configuration for Li-S batteries. Orbital spin splitting in FeCoPS3 drives the electronic structure transition from low-spin to high-spin states, generating more unpaired electrons on the 3d orbit. Specifically, the nondegenerate orbitals involved in the high-spin configuration of FeCoPS3 result in the upshift of energy levels, generating more active electronic states. Such tailored electronic structure increases the charge transfer, influences the d-band center, and further modifies the adsorption energy with lithium polysulfides and the potential reaction pathways. Consequently, the cell with FeCoPS3/NC host exhibits an ultralow capacity decay of 0.037% per cycle over 1000 cycles. This study proposed a general strategy for sculpting geometric configurations to enable spin and orbital topology regulation in Li-S battery catalysts.

Crystal Engineering Enables Cobalt-Based Metal-Organic Frameworks as High-Performance Electrocatalysts for H2O2 Production

Metal-organic frameworks (MOFs) with highly adjustable structures are an emerging family of electrocatalysts in two-electron oxygen reduction reaction (2e-ORR) for H₂O₂ production. However, the development of MOF-based 2e-ORR catalysts with high H₂O₂ selectivity and production rate remains challenging. Herein, an elaborate design with fine control over MOFs at both atomic and nano-scale is demonstrated, enabling the well-known Zn/Co bimetallic zeolite imidazole frameworks (ZnCo-ZIFs) as excellent 2e-ORR electrocatalysts. Experimental results combined with density functional theory simulation have shown that the atomic level control can regulate the role of water molecules participating in the ORR process, and the morphology control over desired facet exposure adjusts the coordination unsaturation degree of active sites. The structural regulation at two length scales leads to synchronous control over both the kinetics and thermodynamics for ORR on bimetallic ZIF catalysts. The optimized ZnCo-ZIF with a Zn/Co molar ratio of 9/1 and predominant {001} facet exposure exhibits a high 2e^- selectivity of ∼100% and a H₂O₂ yield of 4.35 mol g_cat^-1 h^-1. The findings pave a new avenue toward the development of multivariate MOFs as advanced 2e-ORR electrocatalysts.