RuO₂ shows high acidic OER activity as Ir-free catalysts, but this feature also induces lattice-oxygen overactivation, Ru overoxidation, dissolution, and irreversible reconstruction and consequent limited stability. Heterojunctions engineering has emerged as an effective strategy to improve acidic OER catalysts by coupling chemically distinct components besides doping. However, previous studies have mainly emphasized heterostructure construction and performance enhancement, while the atom-level interfacial functions that govern acidic OER activity and stability have been somewhat overlooked. In this review, RuO₂-based heterojunctions are proposed as functional interfacial reactors rather than simple multicomponent composites for acidic OER. Heterointerfaces regulate acidic oxygen evolution through five interconnected functions: electronic coupling, oxygen spillover and redox buffering, interfacial water/proton microenvironment regulation, dual-site cooperation, and balanced lattice-oxygen redox. These functions are individually elucidated using representative Ru-based heterojunctions, including Ru/RuO₂, RuO₂/LiCoO₂, ZrO₂-RuO₂, RuO₂/MoO₃, and RuO₂-CeO₂, to reveal how specific interfacial structures regulate charge redistribution, Ru-O covalency, oxygen-species migration, water/proton dynamics, and cooperative O-O bond formation, thereby enhancing OER activity while suppressing Ru overoxidation and dissolution. This review should also be inspiring for designing Core/shell or loaded RuO₂-based catalysts, and thus provides fundamental understanding for designing durable, low-noble-metal acidic OER catalysts for PEMWE.

Axial coordination was one of the effective strategies for modulating the electronic structure of single-atom catalysts. However, the mechanisms of different axial coordination configurations varied significantly, making it difficult to identify the optimal axial ligand. Here, iron phthalocyanine (FePc) was employed as a model catalyst and loaded onto activated carbon (AC) supports pre-anchored with different heteroatoms (O, N, C) for constructing FePc-based model catalysts with different axial ligand elements. All prepared axial coordination catalysts exhibited excellent activity for the oxygen reduction reaction (ORR), with the performance order of: O>N>C. Through the systematic comparison of these model catalysts, an evaluation of the performance differences in modulating the Fe–N₄ structure by different elements was unified. This work reveals the importance of carbonaceous support for tailoring the performance of macrocyclic molecules in electrocatalysis.

Continuous seawater electrolysis is efficient for green hydrogen production, but some key issues have been overlooked. For example, the accumulated to saturated NaCl in electrolyte is poison to cathode by covering its surface and available active sites. Herein we demonstrate Pt/NiFe Prussian blue analogue (Pt/NiFePBA) electrode can continuously catalyze hydrogen evolution effectively at −500 mA·cm⁻² in a 6 M NaOH electrolyte containing saturated NaCl, without being impeded by the formation of NaCl crystals on the electrode surface, which is in distinct contrast to commercial electrodes. Experimental results indicate that Fe(CN)₆⁴⁻ spontaneously released by Pt/NiFePBA blocks the traditionally preferred basal plane growth of NaCl along {100} facets, but favors its growth along {110} basal plane. This alteration leads to an increased crystallization difficulty of NaCl near the electrode, rendering it halophobic (anti-NaCl precipitation) property. This investigation should shed light on general salt involving process besides the practical implementation of seawater electrolysis.

Zn-air batteries (ZABs) as a potential energy conversion system suffer from low power density (typically ≤ 200 mW·cm⁻²). Recently, three-dimensional (3D) integrated air cathodes have demonstrated promising performance over traditional two-dimensional (2D) plane ones, which is ascribed to enriched active sites and enhanced diffusion, but without experimental evidence. Herein, we applied a bubble pump consumption chronoamperometry (BPCC) method to quantitatively identify the gas diffusion coefficient (D) and effective catalytic sites density (ρ_EC) of the integrated air cathodes for ZABs. Furthermore, the D and ρ_EC values can instruct consequent optimization on the growth of Co embedded N-doped carbon nanotubes (CoNCNTs) on carbon fiber paper (CFP) and aerophilicity tuning, giving 4 times D and 1.3 times ρ_EC over the conventional 2D Pt/C-CFP counterparts. As a result, using the CoNCNTs with half-wave potential of merely 0.78 V vs. RHE (Pt/C: 0.89 V vs. RHE), the superaerophilic CoNCNTs-CFP cathode-based ZABs exhibited a superior peak power density of 245 mW·cm⁻² over traditional 2D Pt/C-CFP counterparts, breaking the threshold of 200 mW·cm⁻². This work reveals the intrinsic feature of the 3D integrated air cathodes by yielding exact D and ρ_EC values, and demonstrates the feasibility of BPCC method for the optimization of integrated electrodes, bypassing trial-and-error strategy.

Pt-based catalysts are used commercially for the hydrogen evolution reaction (HER), even though the low earth abundance and high cost of platinum hinder scale-up applications. Ru metal is a promising alternative catalyst for HER owing to its lower cost but similar metal–hydrogen bond strength to Pt. However, designing an efficient and robust Ru-based electrocatalyst for pH-universal HER is challenging. Herein, we successfully synthesized N-doped carbon (NC) supported ruthenium catalysts with different Ru sizes (single-atoms, nanoclusters and nanoparticles), and then systematically evaluated their performance for HER. Among these catalysts, the Ru nanocluster catalyst (Ru NCs/NC) displayed optimal catalytic performance with overpotentials of only 14, 30, and 32 mV (at 10 mA·cm⁻²) in 1 M KOH, 1 M phosphate buffer saline (PBS), and 0.5 M H₂SO₄, respectively. The corresponding mass activities were 32.2, 12.1 and 8.1 times higher than those of 20 wt.% Pt/C, and also much better than those of the Ru single-atoms (Ru SAs/NC) and Ru nanoparticle (Ru NPs/NC) catalysts, at an overpotential of 100 mV under alkaline, neutral and acidic conditions, respectively. Density functional theory (DFT) calculations revealed that the outstanding HER performance of the Ru NCs/NC catalyst resulted from a strong interaction between the Ru nanoclusters and the N-doped carbon support, which downshifted the d-band center and thus weakened the *H adsorption ability of Ru sites.

Fe-N-C materials with atomically dispersed Fe–N₄ sites could tolerate the poisoning of phosphate, and is regarded as the most promising alternative to costly Pt-based catalysts for the oxygen reduction in high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). However, they still face the critical issue of insufficient activity in phosphoric acid. Herein, we demonstrate a P-doping strategy to increase the activity of Fe-N-C catalyst via a feasible one-pot method. X-ray absorption spectroscopy and electron microscopy with atomic resolution indicated that the P atom is bonded with the N in Fe–N₄ site through C atoms. The as prepared Fe-NCP catalyst shows a half-wave potential of 0.75 V (vs. reversible hydrogen electrode (RHE), 0.1 M H₃PO₄), which is 60 and 40 mV higher than that of Fe-NC and commercial Pt/C catalysts, respectively. More importantly, the Fe-NCP catalyst could deliver a peak power density of 357 mW·cm⁻² in a high temperature fuel cell (160 °C), exceeding the non-noble-metal catalysts ever reported. The enhancement of activity is attributed to the increasing charge density and poisoning tolerance of Fe–N₄ caused by neighboring P. This work not only promotes the practical application of Fe-N-C materials in HT-PEMFCs, but also provides a feasible P-doping method for regulating the structure of single atom site.

Rechargeable aqueous zinc ion batteries (AZIBs) based on manganese dioxide (MnO₂) have received much attention for large-scale energy storage applications, however, their energy density is mainly limited by the one-electron reaction of Mn⁴⁺/Mn³⁺ redox. Herein, Mo doped δ-MnO₂ (Mo-MnO₂) is prepared and used as a high-performance cathode for AZIBs, which delivers an ultrahigh specific capacity of 652 mAh·g⁻¹ at 0.2 A·g⁻¹ based on the two-step two-electron redox reaction of Mn⁴⁺ $\rightleftharpoons$ Mn³⁺ $\rightleftharpoons$ Mn²⁺. Ex-situ structural analysis and density functional theory calculation reveal that the Mo⁵⁺ dopant plays an important role in enhancing the electronic conductivity of Mo-MnO₂ and promoting Jahn–Teller distortion of octahedral [MnO₆] in ZnMn₂O₄, which facilitates the second step redox reaction of Mn³⁺/Mn²⁺. This work provides a novel cathode materials design with multi-electron redox chemistry to achieve high energy density in AZIBs.

Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell, which has already attracted growing popularities. However, current methanol oxidation electrocatalysts fall far short of expectations and suffer from excessive use of noble metal, mediocre activity, and rapid decay. Here we report the Pt anchored on NiFe-LDHs surface hybrid for stable methanol oxidation in alkaline media. Based on the high intrinsic methanol oxidation activity of Pt nanoparticles, the substrates NiFe-LDHs further enhanced anti-poisoning ability and maintained unaffected stability after 200,000 s cycle test compared to commercial Pt/C catalyst. The use of NiFe-LDHs is believed to play the decisive role to evenly disperse Pt nanoparticles on their surface using single atomic dispersed Fe as anchoring sites, making full use of abundant OH groups and subsequent facilitating the oxidative removal of carbonaceous poison on neighboring Pt sites. This work highlights the specialty of NiFe-LDHs in improving the overall efficiency of methanol oxidation reaction.

Porous monolithic catalysts with high specific surface areas, which can not only facilitate heat/mass transfer, but also help to expose active sites, are highly desired in strongly exothermic or endothermic gas–solid phase reactions. In this work, hierarchical spinel monolithic catalysts with a porous woodpile architecture were fabricated via extrusion-based three-dimensional (3D) printing (direct ink writing, DIW in brief) of aluminate-intercalated layered double hydroxide (AI-LDH) followed by low temperature calcination. The intercalation of aluminate in LDH is found crucial to tailor the M²⁺/Al³⁺ ratio, integrate LDH nanosheets into monolithic catalyst, and enable the conversion of LDH to spinel at the temperature as low as 500 °C with high specific surface areas (> 350 m²/g). The rapid mass/heat transfer resulted from the versatile 3D network at macroscale and the highly dispersed and fully exposed active sites benefited from the porous structure at microscale endow the 3D-printed Pd loaded spinel MgAl-mixed metal oxide (3D-AI-Pd/MMO) catalyst with excellent catalytic performance in semi-hydrogenation of acetylene, achieving 100% conversion at 60 °C with more than 84% ethylene selectivity.