【作者】 王晨；

【导师】 王立章；

【作者基本信息】 中国矿业大学 ， 环境工程， 2025， 硕士

【摘要】 工业化引发的有机废水污染与过量CO₂排放问题,催生了传统电催化CO₂还原反应（CO₂RR）技术,但其依赖高能耗的析氧反应（OER）的瓶颈制约了实际应用。本研究提出了一种一体式体系设计,以热力学易氧化的有机污染物氧化反应替代OER,利用Pt阳极与Sn阴极实现污染物-燃料一体式转化。针对真实工况中CO₂匮乏环境,揭示了Sn阴极的电荷差分分布与吸附能调控机制;分析了阴阳极协同反应平衡机理。为定向电极制备及工艺参数优化提供新策略,推动电化学碳减排技术的工业化进程。论文主要成果如下:（1）阳极有机污染物氧化的引入使平均槽电压下降约11.3%,甲酸的法拉第效率从10.9%提高至15.9%,同时单位产甲酸能耗降低了约39.2%。电解质浓度、阳极活性表面积和电化学阻抗对阳极氧化效果和CO₂产量有重要影响。随着阳极Na₂SO₄浓度从0.1 M升至0.5 M,污染物降解量、总有机碳（TOC）去除量、和CO₂产量逐渐增高且在0.5 M达到峰值。但当浓度超过0.5 M后,析氧副反应加剧导致化学需氧量（COD）去除量和CO₂产量出现下降。电化学活性表面积（ECSA）测试表明Pt阳极双电层电容C_dl在0.5?M达到最大值却在0.6?M时略有下降,说明过高盐浓度下离子过度吸附及氧气气泡覆盖活性位点抑制了实际催化活性。电化学阻抗谱（EIS）分析显示在0.5 M时电荷转移电阻R_ct最低但超过0.5 M后R_ct反而增大,进一步证明0.5 M为平衡电荷转移与副反应的最佳浓度。总结出了盐浓度调控下的阳极产气动力学机理:适度提高盐浓度可降低溶液电阻、增加H⁺的累积从而优化传质效果、加速电荷转移和增加电极表面活性位点,从而提高有机污染物氧化效果和CO₂产量;但过高的浓度则会因副反应增强和活性位点被占据削弱反应动力学表现,限制了进一步的氧化效果和CO₂产量。（2）电化学测试证实即使CO₂浓度较低时,仍能实现一定程度的CO₂转化。气体组分配比实验与密度泛函理论（DFT）计算指出,在纯CO₂条件下甲酸产量最高（24.28 mg）,但过量CO₂导致活性位点竞争和传质受阻限制了碳回收效率;在CO₂与O₂比例为2:8时碳抵消系数达到最大。DFT计算表明高CO₂覆盖状态下催化剂表面CO₂吸附能更负,电子密度显著提高（2.69 Mg/m³增至2.73 Mg/m³）从而更有利于稳定反应中间体进而促进甲酸生成。但过度吸附会造成负面影响降低整体的碳利用率。（3）阴阳协同实验表明,虽然甲酸法拉第效率仅为1.10%,但碳抵消系数（U_c）却高达86.98%,说明体系产出的大部分CO₂被回收利用,远高于传统碳还原模式。Sn阴极CO₂还原反应遵循经典的Volmer-Heyrovsky机制,即在高电流密度下,由于CO₂供应不足导致Heyrovsky反应加剧引发析氢反应（HER）并同时产生大量OH?离子引起阴极液碱化从而抑制了CO₂还原效率。综合上述分析,提出了电催化一体式反应器的协同机理,即阳极H?的传输速率与阴极CO₂的传输及吸附速率之间的动态匹配对整体性能至关重要。适宜的电解质浓度可确保H⁺与CO₂供给的高效匹配进而稳定阴极反应环境,显著提高甲酸产量和碳利用率。电解质浓度过低会因H⁺与CO₂供应不足而降低整体甲酸产量;过高时则因电流密度升高和局部p H剧烈变化而破坏界面反应的动态平衡。本研究明确了实现污染物高效降解与CO₂高效转化的内在协同机理,为电催化一体化反应器设计提供了重要理论与实验指导。本论文有图37幅,表4个,参考文献105篇。更多还原

【Abstract】 Industrialization-induced issues of organic wastewater pollution and excessive CO₂ emissions have spurred the development of traditional electrocatalytic CO₂reduction reaction（CO₂RR）technologies;however,their reliance on the high-energy oxygen evolution reaction（OER）presents a bottleneck that limits practical applications.In this study,an integrated system design is proposed in which the oxidation of organic pollutants—which are thermodynamically easier to oxidize—replaces the OER,thereby achieving a one-pot conversion of pollutants into fuels using a Pt anode and an Sn cathode.In the context of real operating conditions characterized by a CO₂-depleted environment,the charge differential distribution and adsorption energy regulation mechanisms on the Sn cathode are elucidated,and the synergistic reaction balance between the anode and cathode is analyzed.This work provides a new strategy for targeted electrode preparation and process parameter optimization,thus advancing the industrialization of electrochemical carbon reduction technologies.The main contributions of this thesis are as follows:The introduction of anodic organic pollutant oxidation reduced the average cell voltage by approximately 11.3%,increased the Faradaic efficiency for formic acid from10.9%to 15.9%,and decreased the energy consumption per unit formic acid by about39.2%.Electrolyte concentration,anode active area,and interfacial impedance all have significant impacts on anodic oxidation performance and CO₂ production.As the Na₂SO₄ concentration at the anode increased from 0.1?M to 0.5?M,pollutant degradation,TOC removal,and CO₂ production all rose,reaching their peaks at 0.5?M.However,when the concentration exceeded 0.5?M,intensified oxygen evolution side reactions caused declines in COD removal and CO₂ production.Electrochemcial Active Surface area measurements showed that the Pt anode’s double-layer capacitance(C_dl)peaked at 0.5?M and fell slightly at 0.6?M,indicating that excessive salt concentrations lead to ion over-adsorption and oxygen bubble coverage of active sites,which inhibit catalytic activity.Electrochemical impedance spectroscopy analysis revealed that the charge transfer resistance(R_ct)was lowest at 0.5?M and increased when the concentration exceeded 0.5?M,further confirming that 0.5?M is the optimal concentration to balance charge transfer and side reactions.In summary,we propose the following kinetics for anode gas production under varied salt concentrations:moderate increases in salt concentration lower solution resistance,promote H⁺accumulation to optimize mass transport,accelerate charge transfer,and increase active sites on the electrode surface—thus enhancing pollutant oxidation and CO₂ production;but excessively high concentrations strengthen side reactions and block active sites,weakening reaction kinetics and limiting further oxidation and CO₂ generation.Electrochemical analysis confirm that a degree of CO₂ conversion is achievable even at low CO₂ concentrations.Gas composition ratio experiments and DFT calculations indicate that under pure CO₂ conditions,formic acid yield is highest（24.28?mg）,but excessive CO₂ leads to competition for active sites and mass transport limitations,thereby restricting carbon recovery efficiency;when the CO₂:O₂ ratio is2:8,the carbon offset coefficient reaches its maximum.DFT shows that under high CO₂coverage,the catalyst’s surface CO₂ adsorption energy becomes more negative and electron density significantly increases（2.69 to 2.73?Mg/m³）,stabilizing intermediates and promoting formic acid formation.However,over-adsorption has adverse effects,reducing overall carbon utilization efficiency.Synergistic anode–cathode experiments reveal that although the formic acid Faradaic efficiency is only 1.10%,the carbon offset coefficient（U_c）is as high as86.98%,indicating that most of the produced CO₂ is recovered—far exceeding traditional CO₂ reduction schemes.It is clarified that the Sn cathode CO₂ reduction follows the classical Volmer–Heyrovsky mechanism:at high current densities,insufficient CO₂ supply intensifies the Heyrovsky step,triggering HER and generating large amounts of OH?,which alkalizes the catholyte and suppresses CO₂ reduction efficiency.Based on these analyses,we propose a synergistic mechanism for the integrated electrocatalytic reactor:the dynamic matching between anode H⁺transport and cathode CO₂ transport and adsorption rates is crucial for overall performance.An optimal electrolyte concentration ensures efficient matching of H?and CO₂ supply,stabilizes the cathode environment,and significantly enhances formic acid yield and carbon utilization efficiency.Electrolyte concentrations that are too low reduce formic acid production due to insufficient H⁺and CO₂ supply;concentrations that are too high disrupt the interfacial reaction balance due to increased current density and drastic local p H changes.This study elucidates the intrinsic synergistic mechanism for achieving efficient pollutant degradation and CO₂ conversion,providing vital theoretical and experimental guidance for the design of integrated electrocatalytic reactors.This thesis has 37 figures,4 tables,and 105 references.更多还原