Transition metal doped ceria catalyst prepared by direct precipitation method for thermocatalytic conversion of carbon dioxide via reverse water gas shift

Abstract

Since the beginning of the industrial revolution, mankind has utilized large amounts of fossil fuels to obtain energy, which has led to the emission of large amounts of greenhouse gases such as carbon dioxide. How to reduce CO2 and utilize CO2 to obtain high-value products has become a hot topic in today's research. The thermocatalytic reduction of CO2 by using renewable H2 is expected to be a potential solution to these challenges. In this experiment, the reverse water gas shift (RWGS) reaction of various loaded transition metal doped cerium (MCeO2) catalysts (M = Fe, Co, Ni and Cu) was investigated. The desired catalysts have been synthesized by utilizing the direct precipitation method. The reverse water gas shift reaction has been extensively studied including reaction tests and some characterizations such as X-ray crystallography (XRD), Brunauer Emmett Teller (BET), Temperature Programmed Desorption (TPD), Inductively coupled plasma - optical emission spectrometry (ICP - OES) etc. In reaction tests, the performance of M-CeO2 was evaluated in terms of conversion and selectivity by varying the temperature (400°C - 600°C). The resulting reaction products were monitored using an on-line infrared analyzer to identify the formation of carbon monoxide (CO), methane (CH4), and unconverted CO2. T-test results show that transition metal doping has a significant effect in enhancing the surface CO2 adsorption and reduction. effects, including high loading of Fe with higher than 56% CO2 conversion and 100% selectivity to CO at 600 °C, Cu with 100% selectivity to CO but lower CO2 conversion, and Co and Ni with significant methanation ability, especially at high loading. In addition, the structures of the catalysts before and after the reaction were investigated using XRD. The binding strength of CO2 on the doped CeO2 surface was investigated using the programmed temperature rise desorption (TPD) method. The effect of specific surface on CO2 adsorption was investigated using BET. This experiment explores the effect of different kinds of transition metal-doped cerium catalysts on the reverse water-gas shift (RWGS) reaction, which reduces excess CO2 emissions and also provides an idea for CO2 conversion and utilization.