Prof. Xinhe Bao’s research team in the State Key Laboratory of Catalysis has recently made research progress in electrochemical reduction of CO₂ (CO₂RR). The results are published in Energy & Environmental Science (Energy Environ. Sci., 2018,11, 1204-1210).

The electrochemical CO₂ reduction is a potentially effective approach to achieve CO₂ conversion and intermittent renewable electricity storage simultaneously, which assists in the construction of a sustainable energy network for carbon resources. In recent years, Prof. Xinhe Bao and Guoxiong Wang’s research team has endeavored to investigate CO₂RR from the perspective of fundamental catalysis, and made great progress on nanosized Pd-based catalyst, metal-oxide interface and CO₂ electrolysis on solid oxide electrolysis cell, significantly improving the selectivity, activity and stability of CO₂RR (J. Am. Chem. Soc., 2015, 137, 4288; Nano Energy, 2016, 27, 35; Chem. Sci., 2017, 8, 2569; J. Am. Chem. Soc., 2017, 139, 5652; ACS Catal., 2018, 8, 1510; Angew. Chem. Int. Ed., 2018, 57, 6054; Nano Energy, 2018, 50, 43; Energy Storage Materials, 2018, 13, 207).

The research team has recently focused on the controllable preparation and electrocatalytic properties of transition metal-nitrogen-carbon composite materials (Energy Environ. Sci., 2016, 9, 3736; Nano Energy, 2017, 38, 281; ACS Catal., 2017, 7, 7638). In the previous research work, transition metal-nitrogen-carbon composite materials have demonstrated impressive Faradaic efficiencies for the CO₂RR. However, the Faradaic efficiencies of the CO₂RR drop rapidly, accompanying an increase in the overpotential in order to achieve high current densities. So far, transition metal-nitrogen-carbon composite materials have suffered the problem of achieving high current density while maintaining high Faradaic efficiency for the CO₂RR, which is essential for the requirements of fast reaction rate and high reaction selectivity in future applications of the CO₂RR.

In this recent published paper, they propose a strategy to facilitate the CO₂RR through the construction of coordinatively unsaturated nickel–nitrogen (Ni–N) active sites within porous carbon, derived from the pyrolysis of Zn/Ni bimetallic zeolitic imidazolate framework-8 (ZIF-8), with a Ni loading as high as 5.44 wt%. The CO Faradaic efficiency is maintained between 92.0% and 98.0% over a wide potential range of -0.53 V to-1.03 V(vs. RHE), while the CO current density increases with the overpotential and reaches an unprecedentedly high value of 71.5 ± 2.9 mA cm^-2 at -1.03 V (vs. RHE). Density functional theory calculations suggest that the CO₂RR occurs more easily than the HER over the coordinatively unsaturated Ni–N site. Thus, both high Faradaic efficiency and current density of the CO₂RR are achieved simultaneously.

This work was financially supported by Natural Science Foundation of China, National Key R&D Program of China, Dalian Institute of Chemical Physics and Strategic Priority Research Program of the Chinese Academy of Sciences. (By Chengcheng Yan and Haobo Li)