Electrochemical co-upgrading CO2 and glycerol for selective formate production with 190% overall faradaic efficiency

The electrochemical carbon dioxide reduction (CO₂RR) technology driven by renewable energy is a promising approach to address environmental and energy issues. Traditionally, cathodic CO₂RR is coupled with anodic oxygen evolution reaction (OER). However, the efficiency of overall electrocatalytic system is limited by the sluggish charge kinetics of OER, which also significantly contributes to the high cell voltages of OER//CO₂RR paired electrolytic system, according to Gibbs free energy analysis. Nowadays, replacing OER with glycerol oxidation reaction (GOR) is considered an effective strategy to reduce energy consumption and improve the economic value of the overall electrolysis system, simultaneously. Whereas, due to the complex reaction pathways of GOR, current GOR electrolysis systems mainly suffer from low product selectivity, high catalyst costs, and poor long-term stability, all of which severely limit the practical application of GOR/CO₂RR paired electrolysis systems. Therefore, achieving efficient electrocatalytic co-upgrading of CO₂ and glycerol remains a significant challenge.

A team led by Ruixiang Li, Michael Grätzel, and Jiaqi Xu recently fabricated a NiOOH@Ni₃S₂ heterojunction catalyst on a nickel foam substrate (NiOOH@Ni₃S₂/NF) via an electrochemical reconstruction method. The Ni²⁺/Ni³⁺ redox couples within the NiOOH@Ni₃S₂ heterojunction enhance the charge transfer kinetics between the active sites and the adsorbed reactant species, facilitating the highly selective and rapid generation of formate from GOR on the NiOOH@Ni₃S₂/NF catalyst. This catalyst exhibits a remarkable Faradaic efficiency (FE) of 94% towards formate generation at a current density of 100 mA cm^-2 in an alkaline flow cell. Comprehensive mechanistic studies revealed that the reaction pathway towards formate generation starts from glyceraldehyde intermediates, with glycolate identified as a key species. The mechanism uncovered in this work offers valuable insights for the rational design of advanced catalysts to the selective production of formate. Coupled with efficient CO₂RR on defect-rich bismuth nanosheets, the team achieved the co-production of formate at both the cathode and anode. The GOR//CO₂RR paired electrolysis system realizes a remarkable overall FE of ca. 190% for formate generation (cathodic FE: 91%; anodic FE: 99%) at a current density of 160 mA cm^-2. This process operated at a cell voltage of ca. 2.32 V, which was about 0.85 V lower than that required for OER//CO₂RR system at the same current density, thereby greatly reducing the energy consumption.

The team published their work in Nano Research on May 6, 2025.

“In this work, we aim to construct an efficient electrochemical system for the co-upgrading of CO₂ and glycerol toward formate production, which not only improves the economic value of the overall reaction but also reduces energy consumption. Moreover, we hope that our comprehensive mechanistic investigations into the GOR process will provide new insights for the readers and contribute to the advancement of this field.” said Siheng Yang.

Other contributors include Dingwen Chen, Xuan Zeng, Xueli Zheng, Haiyan Fu, Weichao Xue, Hua Chen, Shuang Li, Chong Cheng, Ruixiang Li, Jiaqi Xu from Sichuan University in Chengdu, China; Jing Gao, Michael Grätzel from École Polytechnique Fédérale de Lausanne in Lausanne, Switzerland; Jiawei Mao from Sichuan Institute of Product Quality Supervision and Inspection in Chengdu, China; Qinyuan Hu, Xingchen Jiao from Jiangnan University in Wuxi, China; Xiaohan Sun from Northeast Forestry University in Harbin, China; Li Ji from Sichuan Research Institute of Chemical Quality and Safety Testing in Chengdu, China; and Jing Peng from Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences in Shenzhen, China.

This work was supported by National Natural Science Foundation of China (22105133, 22275205, 52273269), Natural Science Foundation of Sichuan Province of China (2022NSFSC0617), Sichuan Science and Technology Program (2023YFH0027), Central Guidance for Local Science and Technology Development Fund Projects (2024ZYD0099), China Scholarship Council, Science and Technology Project of the State Administration for Market Regulation (2022MK111), Fundamental Research Funds for the Central Universities (1082204112I96).

About the Corresponding Authors

Prof. Ruixiang Li obtained Master’s degree and Ph.D. degree from Lanzhou University and City University of Hong Kong, respectively. He is now a professor in Department of Chemistry, Sichuan University. Prof. Li's research interests includes (1) the design and synthesis of homogeneous and heterogeneous catalysts; (2) green and industrial catalysis. Until now, he has published more than 120 papers, presided over 20 national/provincial scientific research projects.

Prof. Michael Grätzel studied chemistry at the Free University of Berlin and performed his doctoral thesis work in at the Technical University Berlin under the supervision of Professor Arnim Henglein. He subsequently was a postdoctoral fellow with Professor Kerry Thomas at the University of Notre Dame, Indiana (USA). Since 1981, he works as Full Professor at EPFL. Prof. Michael Graetzel is an elected member of the Swiss Academy of Technical Sciences, the German Academy of Science (Leopoldina), as well as a foreign member of the Royal Society, the Chinese Academy of Science, and the Royal Spanish Academy of Engineering. Prof. Michael Graetzel is particularly well known for his discovery of mesoscopic dye-sensitized solar cells (named after him “Graetzel cells”), which in turn engendered the advent of perovskite photovoltaics, constituting the most exciting breakthrough in the recent history of photovoltaics. He used his revolutionary concept of three-dimensional junctions of nanocrystals also to realize photo-electrochemical devices for the solar generation of hydrogen and reduction of carbon dioxide as well as for the storage of electricity in lithium-ion insertion batteries.

Dr. Jiaqi Xu received his B.S. degree in Applied Chemistry from Tianjin University in 2014 and Ph.D. degree in Inorganic Chemistry from the University of Science and Technology of China in 2019. He then worked as a postdoctoral fellow at Sichuan University. Currently, he works as the associate research professor at Sichuan University. In 2024, he joins Prof. Michael Grätzel's lab at École Polytechnique Fédérale de Lausanne as a visiting postdoctoral researcher. His interests include the design and fabrication of low-dimensional materials and their applications in CO₂ conversion.

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.