Crystalline/amorphous Bi-BiNiOx electrocatalyst enables efficient concurrent formate production from CO2 and methanol

The electrochemical CO₂ reduction reaction (CO₂RR) to formate offers a promising pathway for CO₂ utilization under mild conditions. However, its practical application has been hampered by the substantial energy consumption of the anodic oxygen evolution reaction (OER), which accounts for over 90% of the total energy input. A potential solution lies in replacing OER with the partial methanol oxidation reaction (MOR), which not only reduces overall energy demand but also enables simultaneous formate production at both electrodes.

Addressing this challenge, the research group led by Professor Junfeng Xie at Shandong Normal University has developed an advanced two-electrode system integrating a nickel foam-supported crystalline/amorphous bismuth‑bismuth nickel oxide composite cathode (Bi‑BiNiO_x/NF) with a β‑Ni(OH)₂ anode. This innovative configuration achieves exceptional formate production efficiency while significantly lowering operational voltage.

The crystalline/amorphous Bi‑BiNiO_x/NF cathode exhibits remarkable CO₂RR performance, reaching a formate Faradaic efficiency of 98.9% at ‑0.90 V versus the reversible hydrogen electrode (RHE) and maintaining over 90.7% efficiency during 72 hours of continuous operation. This high activity and stability are attributed to the Bi‑Ni bimetallic synergy and the crystalline/amorphous heterostructure, which collectively enhance active site exposure and accelerate reaction kinetics.

When integrated into a CO₂RR||MOR system, the full cell operates steadily for 90 hours at 2.2 V and 10 mA·cm^-2, sustaining formate Faradaic efficiencies above 90% at both electrodes. Notably, the system requires a cell voltage of only 1.760 V—193 mV lower than that of conventional CO₂RR||OER systems (1.953 V)—marking a substantial improvement in energy efficiency.

The team’s work was published in Nano Research on October 21, 2025.

Professor Xie, the study’s senior author and a recipient of the Shandong Provincial Outstanding Young Scholar award, explained: “In this work, we developed an integrated system featuring a crystalline/amorphous Bi‑BiNiO_x/NF cathode and a β‑Ni(OH)₂ anode for the simultaneous production of formate.” He further emphasized that the catalyst’s enhanced performance stems from the synergistic interaction between Bi‑Ni bimetallic sites and its unique crystalline/amorphous heterostructure, which together promote active site availability and charge transfer.

Formate is widely recognized as a multifunctional and environmentally benign chemical. It serves as a key industrial intermediate in sectors such as leather, pharmaceuticals, printing, dyeing, and rubber, and is also directly used in formate fuel cells and hydrogen storage systems. Despite growing demand, about 80% of global formate production still relies on the energy‑intensive and hazardous BASF process, which operates at 353 K and 4 MPa using highly toxic carbon monoxide. This method results in high production costs ($1200–1300 per ton) and an estimated annual price increase of 5.6%.

The present work directly addresses these limitations by designing a highly efficient electrocatalytic system that bypasses the energy‑intensive OER step. “A key breakthrough is the integrated CO₂RR||MOR system,” Professor Xie noted. “It achieves 10 mA·cm^-2 at only 1.760 V and maintains stable operation for over 90 hours at 2.2 V, with formate Faraday efficiencies exceeding 90% on both electrodes.”

To thoroughly characterize the Bi‑BiNiO_x/NF electrocatalyst, the team employed a suite of analytical techniques. XRD, SEM, HRTEM, and XPS were used to analyze its morphology, phase composition, and chemical states; electrochemical measurements assessed its performance and stability; and NMR along with gas chromatography enabled qualitative and quantitative analysis of the electrolysis products.

The notable voltage reduction in the coupled system is ascribed to the successful avoidance of OER kinetic limitations and the synergistic effects arising from the optimized catalyst architecture. This study not only demonstrates an energy‑efficient route to formate synthesis but also introduces a novel strategy for CO₂ valorization, highlighting the effectiveness of synergistic optimization between structural engineering and system design.

Other contributors include Zhuangzhuang Ren, Ruihao Wang, Xianghui Pang, Wenqian Zheng, Liheng Sun, Meiqi Wang and Fengcai Lei from the School of Chemistry, Chemical Engineering and Materials Science at Shandong Normal University; and Xu Sun from the University of Jinan.

This work was supported by a College of Chemistry, Chemical Engineering and Materials Science, Key Laboratory of Molecular and Nano Probes (Ministry of Education), Collaborative Innovation Center of Functionalized Probes for Chemical Imaging in Universities of Shandong, Shandong Normal University, Jinan, Shandong, 250014, P. R. China.

The research group led by Professor Junfeng Xie is dedicated to cutting-edge fields including inorganic solid-state synthesis chemistry, electrocatalysis, and electrosynthesis. Prof. Xie has published over100 papers in renowned international journals, including 16 ESI Highly Cited Papers. His work has accumulated more than 17,000 citations with an H-index of 51. For more information, please pay attention to his research homepage https://webofscience.clarivate.cn/wos/author/record/A-9215-2010.

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 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 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.