image: DFT theoretical calculations were carried out to clarify how Cu doping modifies the electronic structure and catalytic behavior of Er2O3. Cu incorporation reduces the catalyst work function and triggers charge redistribution, forming a strong built-in electric field (BIEF) with positively charged Cu sites and negatively polarized Er2O3 matrix. This BIEF greatly enhances CO2 adsorption, shifts the d-band center upward to strengthen binding of the key *CHO intermediate, and facilitates water dissociation to generate abundant active *H species with optimized adsorption-desorption energy. AIMD simulations confirm that the electric field reorients interfacial water into an H-near configuration, shortening the distance between hydrogen atoms and the catalyst surface and enriching near-surface protons. The Gibbs free energy pathway identifies *CHO→*CH2O as the rate-determining step, whose energy barrier is drastically lowered on Cu-Er2O3, especially under the favorable H-near water arrangement. Electron density difference and COHP analyses prove Cu-Er2O3 transfers more electrons to *CHO and forms stronger orbital coupling with this intermediate than pure Er2O3. Overall, Cu doping-induced BIEF engineering optimizes electronic configuration, interfacial water microenvironment, intermediate adsorption and reaction energy barriers, jointly improving the activity and CH4 selectivity of CO2 electroreduction.
Credit: Nano Research, Tsinghua University Press
Interaction between renewable-energy-powered electrochemical CO2 reduction and carbon neutrality goals is paramount to the development of sustainable carbon recycling technologies, which are designed to convert waste CO2 into high-value carbon-neutral fuels and chemicals without fossil fuel consumption. Methane (CH4), a high-energy-density clean fuel compatible with existing natural gas infrastructure, has emerged as an ideal target product of CO2 electroreduction, yet its production is severely hindered by sluggish multi-electron/proton transfer, insufficient proton supply and low methane selectivity.
A team led by Liya Zhou and Anxiang Guan from Guangxi University and Zaiwang Zhao from Inner Mongolia University recently developed atomically dispersed Cu-doped Er2O3 electrocatalysts to tune built-in electric field (BIEF) and interfacial water microenvironment, significantly boosting the efficiency and selectivity of CO2-to-CH4 conversion. Rare-earth oxide-based electrocatalysts with modulated metal doping possess unique 4f electronic configurations, abundant oxygen vacancies and strong metal-support interactions, showing great potential for selective CO2 methanation. Current research is aimed at constructing tailored built-in electric fields on catalyst surfaces to reorient interfacial water molecules, shorten the distance between adsorbed *H intermediates and catalyst surface, and lower the energy barrier of key reaction steps. These interfacial structural modifications can then be used to accelerate proton transfer and optimize the adsorption of critical CO2RR intermediates.
The team published their article in Nano Research on August 24, 2026.
In this work, the research team rationally designed a series of Cu-Er2O3-x catalysts through sequential precipitation and calcination, and systematically uncovered how the built‑in electric field modulates interfacial water configuration and catalytic CO2RR performance. The group comprehensively characterized the atomic dispersion of Cu(I) dopants, electronic redistribution, oxygen vacancy content, and interfacial water evolution, while combining DFT calculations to elucidate the underlying catalytic mechanism. Furthermore, the researchers established a universal strategy relying on built‑in electric field engineering for rare‑earth oxide electrocatalysts to achieve highly selective methane generation.
Pure Er2O3 consists of hexagonal lattice arranged Er3+ and O2- ions with limited CO2 activation capacity and hydrophobic surface property. The unique electronic modulation brought by atomic Cu doping, including charge redistribution between Cu sites and Er2O3 matrix, upward-shifted d-band center and abundant oxygen vacancies, makes Cu-Er2O3 composite an ideal electrocatalyst for CO2 methanation.
The research team elaborates on the synthesis, structural characterization, electrochemical performance and theoretical catalytic mechanism of Cu-doped Er2O3 catalysts tailored for electrocatalytic CO2 conversion to CH4. Moderate Cu doping induces prominent charge redistribution across the material, creating positively charged Cu active sites alongside a negatively polarized Er2O3 substrate. The robust built-in electric field generated by this charge redistribution reorganizes interfacial water into an H-near configuration, shortens the distance between adsorbed *H species and the catalyst surface, accelerates water dissociation to deliver abundant protons, and reinforces the adsorption of the key *CHO intermediate.
One of the core challenges for CO2RR methane electrocatalysts is balancing catalytic activity, CH4 selectivity and long-term operational stability. Excessive Cu doping causes severe lattice distortion and aggregated defects, reducing the number of exposed active sites and weakening catalytic performance. To address this issue, the team precisely controlled Cu doping content and confirmed that Cu-Er2O3-6 delivers optimal performance with balanced oxygen vacancy density, surface hydrophilicity and interfacial electric field strength.
The team anticipates this work will guide the design of advanced rare-earth oxide electrocatalysts and advance practical CO2 recycling electrolysis. Atomic metal doping to construct built-in electric fields serves as a dependable method to adjust interfacial water structures and reaction pathways. Rare-earth-supported Cu catalysts with optimized built-in electric fields will attain higher methane yields and long-term stability for industrial CO2 electrolysis.
Other contributors include Jielian Yang, Bing Chen, Yue Shen, Qi Wu, Yuemei Liao, Jin Guo, Peican Chen from the School of Chemistry and Chemical Engineering, Guangxi University; Naixin Lyu from Department of Chemical Engineering, Carnegie Mellon University; and Zaiwang Zhao from College of Energy Materials and Chemistry, Inner Mongolia University.
This work was supported by the National Natural Science Foundation of China (No. 22465006), Natural Science Foundation of Guangxi Province (No. 2026GXNSFAA00640424), Guangxi Youth Talent Inclusive Support Policy Research Launch Fund (ZX02080030425009), and Guangxi Science and Technology Major Program (Guike AA24263003).
DOI Link:
https://doi.org/10.26599/NR.2026.94908984
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.
Journal
Nano Research
Article Title
Built-in Electric Field-Regulated *H-Catalyst Distance Enables Efficient CO~2~-to-CH~4~ Electroreduction
Article Publication Date
24-Aug-2026