Hydrogen produced by electrochemical water splitting is central to a low-carbon energy system, but its efficiency hinges on the electrocatalyst. Platinum-group metals remain the benchmark for the hydrogen evolution reaction (HER), and their scarcity and cost block large-scale deployment. Transition metal carbides (TMCs) have emerged as promising substitutes because their d-band electronic structure resembles that of platinum, and they conduct electricity well and work over a broad pH range. Unfortunately, primitive unary TMCs bind hydrogen intermediates (H * ) too strongly, which caps their intrinsic activity.
Combining five or more metals in one single-phase solid solution offers a way out. The high-entropy effect can deliver catalytic behaviors far better than any individual component, as already shown for high-entropy alloys and oxides. Yet high-entropy carbide (HEC) catalysts are still in their infancy: multi-metallic elements are chemically immiscible within a carbide lattice, and making nanosized HECs with controlled size is hard. Routes developed so far, such as electrical-discharge-induced bulk-to-nanoparticle transformation, ultra-fast Joule heating, nanoconfined impulse synthesis on carbon nanotube films, pyrolysis of metal-ion-impregnated ZIF-derived carbon and solid-phase combustion synthesis, have all expanded the compositional space. Nevertheless, every material reported to date has been a dense, solid particle.
That is a missed opportunity. Hollow nanostructures offer high surface-to-volume ratios and abundant interior voids, which translate into more exposed active sites, lower mass-transport resistance and shorter charge-transport pathways. Conventional hollow synthesis, however, relies on templates and therefore involves multi-step preparation and often harsh template-removal conditions. In parallel, rare-earth (RE) elements are known to tune the electronic structure of transition-metal alloys and oxides and boost catalytic activity. But rare-earth-containing HEC catalysts remain scarce, largely because the large atomic-size mismatch between rare earths and transition metals hinders the incorporation of rare-earth atoms into the carbide lattice. Fabricating hollow structures and introducing rare earths into HECs are thus two formidable challenges that conventional synthesis struggles to meet simultaneously.
Molten-salt electrolysis offers a mild, low-temperature alternative that converts inexpensive oxide precursors directly into nanomaterials in a single step. Sure, and Schwandt first produced single-phase (NbTaTiZrHf)C nanoparticles of 15-80 nm by electro-deoxidation of a metal oxide/graphite mixture in molten CaCl 2 at 900 °C. Yang and colleagues later coupled anodic CO 2 capture with in situ cathodic carburization (the MSCC-ET process), preparing (NbTaTiZrHf)C of 20-100 nm in a LiCl-CaCl 2 –KCl melt at 980 °C with CO 2 as the sole carbon source, and reported an alkaline HER overpotential of 350 mV at 10 mA·cm -2 with a Tafel slope of 61 mV·dec -1 . Both studies, however, were confined to five-component d-block HECs with solid particulate morphologies.
Now a team led by Wen Ma at the Inner Mongolia Key Laboratory of New Materials and Surface Engineering, Inner Mongolia University of Technology, has broken both barriers at once. The team achieved the first synthesis of hollow nanostructured high-entropy carbides (HfNbTaTiZr)C, (HfNbTaTiZrRE)C (RE = Gd, Ce, Y) and (HfNbTaTiZrCeY)C through a direct electroreduction process. All as-synthesized HECs exhibit a single face-centered cubic phase and compositional homogeneity from the nanoscale to the microscale. Critically, the team found that the microstructure can be tailored from solid to hollow particles simply by selecting a different carbon source, dispensing with templates altogether. When evaluated as HER catalysts in 1.0 M KOH, the engineered hollow architecture combined with rare-earth incorporation substantially enhanced performance, and the dual-rare-earth compositions outperformed their single-rare-earth analogues. The best performer, (HfNbTaTiZrCeY)C, reached an overpotential of just 167 mV at 10 mA·cm -2 with a Tafel slope of 58.8 mV·dec -1 and a charge-transfer resistance of only 2.7 Ω.
The team published their work in Journal of Advanced Ceramics on September 10, 2026 .
“In this study, a family of hollow rare-earth-containing high-entropy carbide (RE-HEC) nanoparticles has been successfully synthesized for the first time. These materials, exhibiting a single face-centered cubic structure, were obtained by a one-pot electroreduction process from oxides and carbon black in molten chlorides at 800 °C.” said wen Ma, professor at School of Materials Science and Engineering at Inner Mongolia University of Technology (China), a senior expert whose research interests focus on the field of functional ceramics material.
“The results show that the microstructure of HECs can be easily tailored from solid to hollow particles by selecting different carbon sources. It was found that the electrocatalytic performance of HECs for HER is noticeably enhanced by the tailored hollow nanostructure compared to their solid counterparts.” said wen Ma.
“These findings collectively demonstrate that the dual RE incorporation into transition-metal-based HECs can not only construct more electroactive sites but also accelerate electrocatalytic kinetics, thereby yielding enhanced HER performance that far surpasses the single-RE counterparts (HfNbTaTiZrRE)C (RE=Ce, Y). This superior activity arises from the synergistic effects of two distinct RE species, Ce and Y.” said wen Ma.
The work establishes a general and facile platform for synthesizing a wide family of hollow rare-earth-containing high-entropy carbide nanoparticles and suggests a new design strategy for high-performance noble-metal-free catalysts. The authors note that further work is needed to clarify how individual rare-earth elements govern the electronic structure and activity.
Other contributors include Hongxia Liu, Jinqiao Zhang, Shiyu Qin and Yu Bai from the School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot, China.
Hongxia Liu is associate professor at the School of Materials Science and Engineering, Inner Mongolia University of Technology, China. Her research focuses on molten salt metallurgy and the fabrication of functional ceramic materials.
Wen Ma is a Level-II Professor and Doctoral Supervisor at Inner Mongolia University of Technology and Director of the Inner Mongolia Key Laboratory of New Materials and Surface Engineering. His research centers on the preparation and technological development of novel functional coatings and advanced ceramic materials. He has led more than 40 research projects funded by the National Natural Science Foundation of China and by Inner Mongolia Autonomous Region, published over 150 papers, and holds 30 granted national invention patents. He received the First Prize of the Natural Science Award of Inner Mongolia Autonomous Region in 2016 and the Second Prize of the Technological Invention Award of the Autonomous Region in 2025.
This work was supported by Carbon Peak and Carbon Neutrality Research Program of Higher Education Institutions in Inner Mongolia Autonomous Region (STZX202227), Natural Science Foundation of Inner Mongolia Autonomous Region (2023MS05020), the National Natural Science Foundation of China (No. 52572074) and Science and Technology Projects of Inner Mongolia Autonomous Region (2025KYPT0027).
DOI LINK : 10.26599/JAC.2026.9221377
About Journal of Advanced Ceramics
Journal of Advanced Ceramics (JAC) is an international academic journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press, and exclusively available via SciOpen . JAC’s 2025 IF is 14, ranking in Top 1 (1/34, Q1) among all journals in “Materials Science, Ceramics” category, and its 2025 CiteScore is 24.6 (6/133) in Scopus database. ResearchGate homepage: https://www.researchgate.net/journal/Journal-of-Advanced-Ceramics-2227-8508
Journal of Advanced Ceramics
Hollow nanostructured rare-earth-containing high-entropy carbides: Facile electrochemical synthesis and effective electrocatalytic performance for hydrogen evolution
10-Sep-2026