The efficiency of proton exchange membrane water electrolysis (PEM-WE) for hydrogen production is heavily dependent on the noble metal iridium-based catalysts. However, the scarcity of iridium limits the large-scale application of PEM-WE. To address this issue, it is promising to select an appropriate support because it not only enhances the utilization efficiency of noble metals but also improve mass transport under high current. Herein, we supported amorphous IrO_x nanosheets onto the hollow TiO₂ sphere (denoted as IrO_x), which demonstrated excellent performance in acidic electrolytic water splitting. Specifically, the annealed IrO_x catalyst at 150 ^oC in air exhibited a mass activity of 1347.5 A g^-1_Ir, which is much higher than that of commercial IrO₂ of 12.33 A g^-1_Ir at the overpotential of 300 mV for oxygen evolution reaction (OER). Meanwhile, the annealed IrO_x exhibited good stability for 600 hours operating at 10mA cm^-2. Moreover, when using IrO_x and annealed IrO_x catalysts for water splitting, a cell voltage as low as 1.485 V can be achieved at 10 mA cm^-2. The cell can continuously operate for 200 hours with negligible degradation of performance.

IrRu bimetallic oxides are recognized as the promising acidic oxygen evolution reaction (OER) catalysts, but breaking the trade-off between their activity and stability is an unresolved question. Meanwhile, addressing the issues of mass transport obstruction of IrRu bimetallic oxides under high current remains a challenge for the development of proton exchange membrane water electrolysis (PEM-WE). Herein, we prepared an IrRuO_x nanomeshes (IrRuO_x NMs) with high coordination number (CN) of Ir–O–Ru bonds in a mixed molten salt with high solubility of the Ir/Ru precursor. X-ray absorption spectroscopy analysis revealed that the IrRuO_x NMs possess high coordination number of Ir–O–Ru bonds (CN_Ir–O–Ru = 5.6) with a distance of 3.18 Å. Moreover, the nanomesh structures of IrRuO_x NMs provided hierarchical channels to accelerate the transport of oxygen and water, thus further improving the electrochemical activity. Consequently, the IrRuO_x NMs as OER catalysts can simultaneously achieve high activity and stability with low overpotential of 196 mV to reach 10 mA·cm⁻² and slightly increase by 70 mV over 650 h test. Differential electrochemical mass spectrometry tests suggest that the preferred OER mechanism for IrRuO_x NMs is the adsorbent evolution mechanism, which is beneficial for the robust structural stability.

Manipulating the oxidation state of Cu catalysts can significantly affect the selectivity and activity of electrocatalytic carbon dioxide reduction (CO₂RR). However, the thermodynamically favorable cathodic reduction to metallic states typically leads to catalytic deactivation. Herein, a defect construction strategy is employed to prepare crystalline/amorphous Cu₂₊₁O/CuO_x heterostructures (c/a-CuO_x) with abundant Cu⁰ and Cu^δ+ (0 < δ < 1) sites for CO₂RR. The C₂₊ Faradaic efficiency of the heterostructured Cu catalyst is up to 81.3%, with partial current densities of 406.7 mA·cm⁻². Significantly, real-time monitoring of the Cu oxidation state evolution by in-situ Raman spectroscopy confirms the stability of Cu^δ+ species under long-term high current density operation. Density functional theory (DFT) calculations further reveal that the adjacent Cu⁰ and Cu^δ+ sites in heterostructured c/a-CuO_x can efficiently reduce the energy barrier of CO coupling for C₂₊ products.

The advancement of lithium-sulfur (Li-S) batteries is severely retarded by lithium polysulfides (LiPSs) shuttling behavior and sluggish redox kinetics. Herein, the heterogeneous composite with defective Bi₂Se_3−x nanosheets and porous nitrogen-doped carbon (Bi₂Se_3−x/NC) is prepared by selenizing bismuth metal-organic frameworks as a multifunctional sulfur host. The highly efficient immobilization-conversion on LiPSs is realized by the synergistic effect of structure construction strategy and defect engineering. It is found that Bi₂Se_3−x with the suitable amount of selenium vacancies achieves the best electrochemical performance due to the advantages of its structure and composition. These results confirm the intrinsic correlation between defects and catalysis, which are revealed by computational and experimental studies. Due to these superiorities, the developed sulfur electrodes exhibited admirable stability and a fairly lower capacity decay rate of approximately 0.0278% per cycle over 1,000 cycles at a 3 C rate. Even at the high sulfur loading of 6.2 mg·cm⁻², the cathode still demonstrates a high discharge capacity of 455 mAh·g⁻¹ at 1 C. This work may enlighten the development of mechanism investigation and design principles regarding sulfur catalysis toward high-performance Li-S batteries.

The basal planes of transition metal dichalcogenides are basically inert for catalysis due to the absence of adsorption and activation sites, which substantially limit their catalytic application. Herein, a facile strategy to activate the basal plane of WS₂ for hydrogen evolution reaction (HER) catalysis by phosphorous-induced electron density modulation is demonstrated. The optimized P doped WS₂ (P-WS₂) nanowires arrays deliver a low overpotential of 88 mV at 10 mA·cm⁻² with a Tafel slope of 62 mV·dec⁻¹ for HER, which is substantially better than the pristine counterpart. X-ray photoelectron spectroscopy confirms the surface electron densities of WS₂ have been availably manipulated by P doping. Moreover, density functional theory (DFT) studies further prove P doping can redistribute the density of states (DOS) around E_F, which endow the inert basal plane of P-WS₂ with edge-like catalytic activity toward hydrogen evolution catalysis. Our work offers a facile and effective approach to modulate the catalytic surface of WS₂ toward highly efficient HER catalysis.

The high unoccupied d band energy of Ni₃N basically results in weak orbital coupling with water molecule, consequently leading to slow water dissociation kinetics. Herein, we demonstrate Cr doping can downshift the unoccupied d orbitals and strengthen the interfacial orbital coupling to boost the water dissociation kinetics. The prepared Cr-Ni₃N/Ni displays an impressive overpotential of 37 mV at 10 mA·cm_geo^-2, close to the benchmark Pt/C in 1.0 M KOH solution. Refined structural analysis reveals the Cr dopant exists as the Cr-N₆ states and the average d band energy of Ni₃N is also lowered. Density functional theory calculation further confirms the downshifted d band energy can strengthen the orbital coupling between the unpaired electrons in O 2p and the unoccupied state of Ni 3d, which thus facilitates the water adsorption and dissociation. The work provides a new concept to achieve on-demand functions for hydrogen evolution catalysis and beyond, by regulating the interfacial orbital coupling.

Molybdenum disulfide (MoS₂) has been recognized as one of the most promising candidates to replace precious Pt for hydrogen evolution reaction (HER) catalysis, due to the natural abundance, low cost, tunable electronic properties, and excellent chemical stability. Although notable processes have been achieved in the past decades, their performance is still far less than that of Pt. Searching effective strategies to boosting their HER performance is still the primary goal. In this review, the recent process of the electronic regulation of MoS₂ for HER is summarized, including band structure engineering, electronic state modulation, orbital orientation regulation, interface engineering. Last, the key challenges and opportunities in the development of MoS₂-based materials for electrochemical HER are also discussed.