Abstract:

The cellulose fiber that was first-loaded and then carbonized CuO-ZnO-biochar(CuO-ZnO-C_L+C) composites, was prepared using softwood bleached kraft pulp(SBKP) as the carrier and loading CuO-ZnO followed by carbonization. The effects of carrier loading and the sequence of carbonization on the CuO-ZnO loading in the composites were investigated by scanning electron microscope(SEM), inductively coupled plasma mass spectrometry(ICP-MS), X-ray diffraction(XRD), dual constant potential instrumentation, and vacuum photocatalytic reduction of CO₂ system. The results showed that the carbonized and then loaded biochar(C_C+L) was only physically mixed with CuO and ZnO, and there was no hydroxyl group on its surface to adsorb and immobilize the catalyst. It was very easy to agglomerate, and the CuO content of the resulting CuO-ZnO-C_C+L composite was not as high as CuO-ZnO-C_L+C. The crystalline shape of the CuO-ZnO-C_L+C composite was more complete, with higher photocurrent intensity, smaller resistance, and better photocatalytic reduction of CO₂ activity. The effects of the ratio of the amount of Cu²⁺ to Zn²⁺, the carbonization temperature of the composites, and the diameter of the cellulose fibers on the prepared CuO-ZnO-C_L+C were investigated with CO yield as the index. The results showed that: when SBKP was used as the cellulose template under the condition of the molar ratio of Cu²⁺ to Zn²⁺ of 1∶6 and the compositing temperature of 500 ℃, the prepared CuO-ZnO-C_L+C contained 64.86% carbon, CuO and ZnO loadings were 10.94% and 26.50%, respectively, and the yield of photocatalytic reduction of CO₂ to CO reached a maximum value of 0.22 mmol/(g·h), CH₄ yield was 0.043 mmol/(g·h), with a selectivity of CO as high as 83.7%.

Key words: biochar, photocatalysis, CO₂