Author: Hongxia Wang, Yan-Kai Tzeng, Yongfei Ji.
Corresponding author: Yi Cui, Steven Chu, Tan Tianwei, Karen Chan
Communication unit: Stanford University, Beijing University of Chemical Technology, SLAC National Accelerator Laboratory

Research highlights:
1. A new catalytic interface for Cu-nitrogen doped nanodiamonds has been developed.
2. Achieved excellent catalytic performance of C2 product from CO2 reduction.

Carbon-neutral energy conversion processes are critical to global climate change and energy issues. The development of CO2 reduction to produce high-value chemical catalysts is a key issue with great prospects and challenges in the energy and environmental fields. The electrochemical reduction method is more and more dominant in CO2 reduction due to its advantages such as simple operation, mild environment and superior performance.

For most CO2 reduction catalysts, the general product is often C1 products such as CO or HCOOH. Recently, catalysts that can realize multi-carbon (C≥2) high value-added chemicals in neutral aqueous media have slowly appeared. A common problem with these catalysts is that the potential used is too low, typically -0.9V (vs RHE) or lower. In addition, problems such as low yield and poor long-term stability abound.

In view of this, the Cui Yi team at Stanford University, together with Nobel Prize winner Professor Zhu Yiwen, Beijing University of Chemical Technology Tan Tianwei and others, reported a highly selective and stable catalytic interface design strategy based on copper nanoparticles for heterogeneous Phase-catalyzed CO2 to produce C2 high-value chemicals.

Figure 1. Schematic of material preparation

The researchers constructed a nitrogen-doped nanodiamond / Cu nanoparticle interface. The reason for constructing this interface is, on the one hand, because of the existing CO2 reduction catalysts, copper-based nanocatalysts are undoubtedly the best. On the other hand, nitrogen-doped nanodiamonds have low cost, high electrochemical activity, large surface area, and have chemical stability of europium. In addition, nitrogen-doped nanodiamonds contain a large amount of N-sp3 C components, and previous studies have found that they are essential for electrocatalytic activity. Therefore, the research team hopes that by constructing a multi-component interface, more possibilities for synergistic C-C bonding can be realized.

Figure 2. Characterization of N-ND / Cu electrode materials

Studies have shown that the Faraday efficiency of the catalytic preparation of C2 products is about 63% (-0.5 V, RHE). This catalyst unexpectedly exhibits unparalleled high stable catalytic performance, with only 19% activity decay after 120 h. DFT calculations show that the binding force of CO at the Cu / nano-diamond interface is enhanced and CO desorption is inhibited. By reducing the apparent energy barrier of CO dimerization, the production of C2 products is promoted. By adjusting the intrinsic composition and electronic structure of the catalyst, the optimization of the catalytic interface, as well as the thermodynamics and kinetics of the reaction has been achieved.Figure 3. DFT calculation

In short, this research provides a new idea for the design of high-value chemical catalysts from CO2 reduction and brings more possibilities for high-value chemicals from CO2 reduction.

references:
Hongxia Wang et al. Synergistic enhancement of electrocatalytic CO2 reduction to C2 oxygenates at nitrogen-doped nanodiamonds / Cuinterface. Nature Nanotechnology 2020.
https://www.nature.com/articles/s41565-019-0603-y

Source-WeChat public: Nanoman