Interfacial Regulation And Modification Of CuPc/gC₃N₄ Heterojunction CO₂ Reduction Photocatalysts

In the context of the national two-carbon strategy,photocatalytic reduction of CO₂ is the key to solving energy and environmental problems and achieving the goals of"carbon peaking"and"carbon neutrality".Graphitic carbon nitride（g-C₃N₄）,as an environmentally friendly organic two-dimensional semiconductor photocatalytic material,has become a research hotspot in the field of CO₂ reduction due to its reasonable energy band structure and narrow band gap.However,g-C₃N₄ still has the key problems of easy recombination of photogenerated carriers and insufficient surface catalytic ability,which seriously restrict its photocatalytic performance.Copper phthalocyanine（CuPc）has the advantages of narrow band gap and catalytic activity endowed by the central metal,and its heterojunction with g-C₃N₄can effectively promote the charge separation of g-C₃N₄,and can introduce metal catalytic sites,thereby to a certain extent,the scientific problem of g-C₃N₄ can be solved,and then better photocatalytic performance can be obtained.However,the g-C₃N₄ surface lacks the anchoring sites for CuPc,which leads to the self-aggregation of CuPc on the g-C₃N₄ surface,which is not conducive to the high loading of CuPc and the exposure of effective catalytic sites.In addition,the catalytic ability of CuPc central metal ion(Cu²⁺)also needs to be further improved.Based on this,this paper mainly carries out the following two aspects:（1）Graphene（G）-induced assembly of copper phthalocyanine（CuPc）/G/g-C₃N₄complexes and their visible-light catalytic CO₂reduction performance.Based on the preparation of ultrathin g-C₃N₄（UCN）by acid-oxidative exfoliation method,the loading of G on its surface was realized by hydroxyl group induction,furthermore,the high-quantity and high-dispersion modification of CuPc on the G/g-C₃N₄ surface was achieved through hydrogen bond induction.The photocatalytic CO₂ reduction performance of the best composite is about 6 times higher than that of pure g-C₃N₄.Based on the results of AFM,SS-SPS,TR-PL and single-wavelength photocurrent interaction spectra,it was shown that CuPc as a high-level electron accepting platform can effectively promote the photogenerated charge separation of UCN,and CuPc has a certain catalytic effect on CO₂reduction.However,CuPc tends to self-aggregate at higher loadings,which is not conducive to the transfer and reaction of photogenerated electrons in the composite.The interface regulation effect of G is beneficial to the dispersion of CuPc,which can greatly increase its effective loading,and can improve the electron transport at the interface of UCN and CuPc,thereby significantly improving the high-level electron transfer efficiency between the two and promoting the photogenerated charge.separation and increase its activity.（2）The regulation and mechanism of CuPc/G/UCN complex mixed valence(Cu⁺/Cu²⁺)catalytic center.Aiming at the unsatisfactory ability of Cu²⁺central ions in CuPc to catalyze CO₂ reduction,a strategy for partial reduction of CuPc central Cuions in CuPc/G/UCN composites by hydrogenation was proposed.The performance of the best sample after hydrogenation is 2.5 times that before hydrogenation.The results show that the hydrogenation process changes the coordination environment of Cuions and converts part of Cu²⁺into Cu⁺,and the presence of mixed-valent copper ions greatly improves the ability of the complex to catalyze and activate CO₂,thereby greatly improving its photocatalytic performance.