The continuous increase in the consumption of coal, oil, and natural gas has not only led to the depletion of unsustainable energy sources, but has also caused excessive CO₂ emissions, thus resulting in serious energy crises and climate issues. In such a scenario, it is imperative to explore clean and sustainable energy conversion technologies to address the escalating energy demands and environmental crises. Photocatalytic CO₂ conversion, inspired by natural photosynthesis, utilizes solar energy to convert CO₂ and water into valuable chemicals. After decades of development, artificial photosynthesis has emerged as a green, cost-effective, and sustainable approach to achieving carbon neutrality. However, the challenges of low carrier separation efficiency and insufficient active sites in photocatalysts remain significant hurdles in achieving high-performance CO₂ photoreduction. To address this challenge, the integration of metal nanoparticles with semiconductors to create an Ohmic junction can enhance electron-hole migration by the assist of interfacial electric field (IEF). In this study, an Ohmic junction photocatalyst is constructed by in situ formation of Bi nanoparticles on the surface of BiOCl nanosheets through a solvothermal process. The composition and morphology of the photocatalysts were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) was employed to assess the light absorption performance of the photocatalyst. Transient photocurrent response, electrochemical impedance spectroscopy (EIS), and electron spin resonance (ESR) were utilized to evaluate the efficiency of electron-hole transfer. The distinct work function difference between Bi nanoparticles and BiOCl nanosheets leads to favorable charge transfer characteristics within the formed Ohmic junction, significantly improving the utilization efficiency of photogenerated carriers. Besides, the Bi nanoparticles serve as co-catalysts, enhancing the activation of inert CO₂. As a result, the optimized Bi/BiOCl composite (Bi/BiOCl-2) exhibits enhanced generation rates of CO (34.31 µmol·g⁻¹) and CH4 (1.57 µmol g⁻¹) during 4-h of irradiation, which is 2.55 and 4.76 times compared to pristine BiOCl nanosheets, respectively. Isotope tracer experiments suggest that the obtained carbon-based products are generated through CO₂ photoreduction in the presence of water molecule under irradiation. Moreover, in situ Fourier-transform infrared spectroscopy (in situ FTIR) results indicate the formation of *CHO, *CH₃O, b-CO₃²⁻, m-CO₃²⁻, HCO⁻₃, HCOOH, *COOH, and HCOO⁻ species during the CO₂ reduction process and a possible mechanism for CO₂ photoreduction into CO and CH₄ is proposed based on these findings. After 25-h of CO₂ photoreduction reaction, the yields of CO and CH₄ continue to increase. Furthermore, the stability of the prepared material is confirmed by XRD pattern, XPS analysis, and TEM image. These outcomes underscore an effective strategy for constructing advanced photocatalysts tailored for high-performance solar-driven CO₂ reduction. © Editorial office of Acta Physico-Chimica Sinica.

煤炭、石油和天然氣等能源的不斷增長消耗，不僅導致不可再生能源逐漸枯竭，還使大氣中的CO₂濃度顯著上升，引發嚴重的能源危機和氣候問題。因此，我們必須開發清潔、可持續的能源轉換技術，以應對不斷增長的能源需求和日益嚴重的環境危機。受到自然界光合作用的啟發，光催化CO₂轉化利用太陽能驅動，可以將CO₂和水轉化為高附加值的化學品。經過多年的發展，人工光合作用已被認為是一種綠色、經濟、可持續的方法，有望助力實現國家的碳中和發展目標。然而，現有的光催化劑存在著載流子分離效率低和活性位點不足的問題，從而導致CO₂光還原效率較低。為了應對這些科學問題，研究人員發現將金屬納米粒子負載到半導體材料上形成歐姆結，可以產生內建電場，有助於光生電子和空穴的分離。因此，本研究通過溶劑熱法在BiOCl納米片表面負載Bi納米粒子，構建了Bi/BiOCl歐姆結光催化劑。通過X射線衍射(XRD)、X射線光電子能譜(XPS)和透射電子顯微鏡(TEM)分析了光催化劑的成分和微觀結構。利用紫外-可見漫反射光譜(UV-Vis DRS)研究了催化劑的光吸收性能。通過瞬態光電流回應測試、電化學阻抗譜(EIS)和電子自旋共振譜(ESR)研究了光生電子和空穴的分離能力。由於Bi納米粒子與BiOCl的功函數不同，二者形成的歐姆結具有優異的電荷轉移特性，可以顯著提高光生載流子的利用效率。此外，Bi納米粒子還可以作為助催化劑，促進惰性CO₂分子的活化。光催化測試結果顯示，經過300 W氙燈照射4 h後，具有最佳活性的複合材料(Bi/BiOCl-2)將CO₂還原為CO (34.31 µmol·g⁻¹)和CH₄ (1.57 µmol·g⁻¹)的速率分別是BiOCl納米片的2.55倍和4.76倍。同位素示蹤實驗證實，產物是CO₂和水分子經過光催化反應得到的。此外，根據原位傅裡葉變換紅外光譜(in situ FTIR)結果，發現在CO₂還原過程中形成了*CHO、*CH₃O、b-CO₃²⁻、m-CO₃²⁻、HCO⁻₃、HCOOH、*COOH和HCOO⁻等中間體，並進一步提出了可能的光催化CO2還原機制。經過25 h的CO₂光還原反應後，CO和CH₄產量持續增加，同時結合XRD、XPS和TEM結果表明，製備的Bi/BiOCl-2材料具有良好的結構穩定性。這項研究為高效CO₂光還原催化劑的構建提供了有益的參考。