关键词: CO₂电催化, 水热法, 泡沫镍, CoO纳米花

Abstract:

The worldwide extensive release of carbon dioxide (CO₂) has caused serious environmental pollution and unprecedented climate change problems. Thus, for the sustainable development of human society, it is very necessary to convert CO₂ to renewable fuels through clean and economical processes. The electrochemical CO₂ reduction reaction (CO₂RR) is regarded as a promising approach for the recycling of carbon resource and the generation of sustainable fuels. However, the slow kinetics and formation of multiple products in CO₂RR hinder its large-scale application. Hence, great research efforts are made to develop electrocatalysts with high product selectivity at low overpotential. Recently, nanostructured transition metal oxide based electrocatalysts have displayed quite exciting performances for the CO₂RR, in terms of fast kinetics, selectivity and durability. Among the various metal oxides, cobalt oxides show high CO₂RR activity, and selective for the formation of formic acid. In this paper, a hybrid of CoO nanoflowers grown onto three-dimensional (3D) reduced graphene oxide (RGO)@Ni foam (CoO/RGO@NF) was synthesized by a facile hydrothermal method. The composite electrode of CoO/RGO@NF was characterized by XRD and SEM. It is found that the CoO nanoflowers grew uniformly on the 3D network of RGO@NF electrode. The CoO nanoflowers were formed by a large number of nanorods around a center. The length of the nanorods was about 10 ~ 15 μm, and the diameter was about 100 ~ 200 nm. The electrocatalytic performance of CoO/RGO@NF composite electrode for CO₂ reduction was studied by cyclic voltammetry and linear scanning voltammetry. The results showed that the current efficiency of CoO/RGO@NF electrode for electrocatalytic reduction of CO₂ was 70.9% and the Faraday efficiency for formic acid production was 65.2%. In addition, the yield of formic acid on the electrode was 59.8 μmol·h^-1·cm^-2 at -0.76 V(vs. SHE) after 4 h of electrolysis. Furthermore, the current density was stable at about 90%. These data indicated that the as-prepared CoO/RGO@NF composite electrode had achieved excellent catalytic activity, selectivity and stability for CO₂ electroreduction.

Key words: CO₂ electrocatalysis, hydrothermal method, nickel foam, CoO nanoflowers