Kaixin Zhu

The development of highly efficient and durable electrocatalysts for water electrolysis is fundamentally constrained by sluggish reaction kinetics, limited active-site regulation, and structural degradation under harsh operating conditions. High-entropy materials (HEMs), featuring maximized compositional diversity and configurational entropy, have emerged as versatile platforms for catalytic optimization. However, the rational incorporation of rare-earth (RE) elements into high-entropy systems and their intrinsic roles in regulating catalytic behavior remain largely unexplored. Owing to their unique electronic configurations, large atomic size mismatch, variable oxidation states, and strong affinity toward oxygen species, RE elements provides additional opportunities to manipulate electronic structures, lattice distortion, defect chemistry, and surface reconstruction behaviors within high-entropy frameworks. Rather than cataloguing individual catalyst systems, this review critically organizes RE-regulated HEMs along a structure-activity chain linking the high-entropy host and RE incorporation to local coordination/electronic effects, catalytic pathways, operando reconstruction, and long-term stability. The fundamental design principles and various modulation strategies, along with their catalytic applications toward the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall/seawater electrolysis are discussed, along with emphasis on the structure-activity relationships revealed by advanced characterization techniques and theoretical calculations. Finally, the remaining challenges and perspectives associated with RE incorporation regarding the activity-stability trade-off, long-term structural evolution, resource efficiency, and practical scalability are analyzed, aiming to offer guidelines for the rational design of RE-engineered high-entropy electrocatalysts with optimized activity, stability, and practical applicability for sustainable energy conversion technologies.

Ammonia, as an essential chemical, plays an indispensable role in both industry and agriculture. However, the traditional Haber–Bosch technique for ammonia synthesis suffers from high energy consumption and significant CO₂ emissions. Therefore, developing an energy-efficient and eco-friendly method for ammonia production is imperative. Photoelectrochemical (PEC) nitrate reduction to ammonia has emerged as a promising green alternative, which utilizes renewable solar energy to convert nitrate into valuable ammonia, thereby contributing to nitrogen recycling and wastewater remediation. This review systematically summarizes recent advances in PEC nitrate reduction to ammonia, focusing on the rational design of efficient photocathodes with the development of semiconductor materials, cocatalysts, p–n junction and heterostructure strategies. Furthermore, the integration of photocathodes with photoanodes enables the assembly of bias-free PEC systems capable of simultaneously producing ammonia and value-added chemicals, demonstrating the potential for scalable solar-driven ammonia synthesis. The mechanistic studies and future research directions are also discussed. The review aims to offer valuable insights and promote the further development of PEC nitrate reduction to ammonia.

Rapid industrial growth has overexploited fossil fuels, making hydrogen energy a crucial research area for its high energy and zero carbon emissions. Water electrolysis is a promising method as it is greenhouse gas-free and energy-efficient. However, OER, a slow multi-electron transfer process, is the limiting step. Thus, developing efficient, low-cost, abundant electrocatalysts is vital for large-scale water electrolysis. In this paper, the application and progress of transition metal chalcogenides (TMCs) as catalysts for the oxygen evolution reaction in recent years are comprehensively reviewed. The key findings highlight the catalytic mechanism and performance of TMCs synthesized using single or multiple transition metals. Notably, modifications through recombination, heterogeneous interface engineering, vacancy, and atom doping are found to effectively regulate the electronic structure of metal chalcogenides, increasing the number of active centers and reducing the adsorption energy of reaction intermediates and energy barriers in OER. The paper further discusses the shortcomings and challenges of TMCs as OER catalysts, including low electrical conductivity, limited active sites, and insufficient stability under harsh conditions. Finally, potential research directions for developing new TMC catalysts with enhanced efficiency and stability are proposed.

L-cysteine, a component of the symmetric L-cystine, is essential in numerous biological activities. Thus, detecting cysteine rapidly, selectively, and sensitively is of tremendous interest. Herein, g-C₃N₄@CdS composites were employed as sensing elements in a photoelectrochemical platform for L-cysteine sensing. In this system, g-C₃N₄@CdS composites provided much better optoelectronic function than bare CdS materials owing to their high photon-to-current conversion efficiency and excellent anti-photocorrosion properties. The innovative photoelectrochemical sensor has a wide determination range of 5 to 190 µM, a very low detection limit of 1.56 µM, a fast response time, and good long-term stability (ca. 1 month). Without applying any separation procedures, a low concentration of CySH was successfully detected in human urine samples, which is compatible with the results of chemiluminescence.

Ruthenium (Ru) has been considered a promising electrocatalyst for electrochemical hydrogen evolution reaction (HER) while its performance is limited due to the problems of particle aggregation and competitive adsorption of the reaction intermediates. Herein, we reported the synthesis of a zinc (Zn) modified Ru nanocluster electrocatalyst anchored on multiwalled carbon nanotubes (Ru-Zn/MWCNTs). The Ru-Zn catalysts were found to be highly dispersed on the MWCNTs substrate. Moreover, the Ru-Zn/MWCNTs exhibited low overpotentials of 26 and 119 mV for achieving current intensities of 10 and 100 mA cm⁻² under alkaline conditions, respectively, surpassing Ru/MWCNTs with the same Ru loading and the commercial 5 wt% Pt/C (47 and 270 mV). Moreover, the Ru-Zn/MWCNTs showed greatly enhanced stability compared to Ru/MWCNTs with no significant decay after 10,000 cycles of CV sweeps and long-term operation for 90 h. The incorporation of Zn species was found to modify the electronic structure of the Ru active species and thus modulate the adsorption energy of the H_ad and OH_ad intermediates, which could be the main reason for the enhanced HER performance. This study provides a strategy to develop efficient and stable electrocatalysts towards the clean energy conversion field.

Developing earth-abundant electrocatalysts useful for hydrogen evolution reactions (HER) is critical for electrocatalytic water splitting driven by renewable energy. Molybdenum carbide (Mo₂C) with the crystal structure of hexagonal symmetry has been identified to be an excellent HER catalyst due to its platinum-like electronic structure while the synthesis of Mo₂C is generally time consuming and energy intensive. Herein, we demonstrated the ultrafast synthesis of a Mo₂C-based electrocatalyst with Joule heating at 1473 K for only 6 s. Benefitting from several advantages including efficient catalytic kinetics, enhanced charge transport kinetics and high intrinsic activity, the as-prepared catalyst exhibited drastically enhanced HER performance compared with commercial Mo₂C. It showed an overpotential of 288 mV for achieving a current density of −50 mA cm⁻² and good stability, which highlighted the feasibility of the Joule heating method towards preparing efficient electrocatalysts.