本文以氧化石墨烯包覆泡沫镍电极(GO@NF)作为基底,采用水热法在GO@NF基底上原位生长CoO纳米花,同时GO在水热过程中被同步热还原为还原氧化石墨烯(RGO),从而一步制得还原氧化石墨烯包覆泡沫镍负载CoO纳米花电极(CoO/RGO@NF)。使用XRD和SEM对CoO/RGO@NF电极进行表征,发现CoO纳米花均匀生长在泡沫镍三维网络结构上,CoO纳米花为大量针状纳米棒围绕一个中心而成的花状结构,纳米棒的长度约为10 ~ 15 μm,直径约为100 ~ 200 nm。使用循环伏安和线性扫描法测试了CoO/RGO@NF电极电催化CO₂的还原性能,在-0.76 V（vs. SHE）电位下,CoO/RGO@NF电极电催化CO₂还原的电流效率达到70.9%,产甲酸法拉第效率达到65.2%,甲酸产率为59.8 μmol·h^-1·cm^-2,且电极可持续稳定电催化还原CO₂ 4 h,表明CoO/RGO@NF电极对CO₂电还原有着优良的催化活性、选择性和稳定性。

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.