Electrochemical reduction of CO2 into high-value hydrocarbons and alcohols by using Cu-based catalysts is a promising and attractive technology for CO2 capture and utilization, resulting from their high catalytic activity and selectivity. The mobility and accessibility of active sites in Cu-based catalysts significantly hinder the development of efficient Cu-based catalysts for CO2 electrochemical reduction reaction (CO2RR). Herein, a facile and effective strategy is developed to engineer accessible and structural stable Cu sites by incorporating single atomic Cu into the nitrogen cavities of the host graphitic carbon nitride (g-C3N4) as the active sites for CO2-to-CH4 conversion in CO2RR. By regulating the coordination and density of Cu sites in g-C3N4, an optimal catalyst corresponding to a one Cu atom in one nitrogen cavity reaches the highest CH4 Faraday efficiency of 49.04% and produces the products with a high CH4/C2H4 ratio over 9. This work provides the first experimental study on g-C3N4-supported single Cu atom catalyst for efficient CH4 production from CO2RR and suggests a principle in designing highly stable and selective high-efficiency Cu-based catalysts for CO2RR by engineering Cu active sites in 2D materials with porous crystal structures.

研究不同的工艺参数对Tedlar复合材料-铝薄膜(厚度为2 μm)表面形貌的影响,理论优化得到合理的工艺参数。研究结果表明,单位时间内极多数量飞秒激光脉冲的积累作用,使得铝膜表面的作用区域温度在极短时间内快速升高并超过铝的熔点和气化温度,表面铝膜最终被刻蚀去除;当激光功率增大到5.5 W时,界面处温度达到了513.19 K,超过了基底Tedlar材料的最高使用温度,并在基底材料表面烧蚀产生点坑;当扫描速度从350 mm/s增大至600 mm/s时,出现的间断点尺寸从1.2 μm增大到2.7 μm,造成激光刻蚀加工尺寸误差高于10 μm;在激光输出功率为4.0 W、光斑直径为40 μm和扫描速率为500 mm/s的工艺条件下,铝膜图形激光刻蚀后尺寸精度及相对位置精度均优于10 μm,满足技术要求。

为了研究移动脉冲激光刻蚀单/双层金属/聚酰亚胺基复合材料的规律, 利用有限元方法建立了移动纳秒脉冲激光刻蚀的通用模型, 讨论了移动速度对激光刻蚀深度的影响, 分析了金属铝薄膜和双层金属膜在移动脉冲激光作用下的温度变化规律。结果表明, 当激光移动速率一定时, 刻蚀深度开始时不断增加, 但增加幅度逐渐减小, 刻蚀深度逐渐趋于一定值, 即达到最大刻蚀深度; 金属与基底材料界面处的温度变化相较于金属薄膜靠近光源处的在时间上有一定滞后, 基底温度在激光关闭后可继续上升; 刻蚀双层金属膜时, 下层选用较厚且热导率较大的金属薄膜有利于保护聚酰亚胺基底。

为了研究1064 nm 激光刻蚀聚酰亚胺基底镀铝薄膜的作用机理，采用有限元分析软件ANSYS模拟了激光对聚酰亚胺基底上铝薄膜的刻蚀过程，分析了激光脉冲作用于铝薄膜表面时的能量传输及转化过程，获得了铝薄膜及聚酰亚胺基底中的温度场分布，进一步验证了在脉冲激光作用下由于基底材料易分解而产生的薄膜/基底界面分离机制。

通过分析激光脉冲作用于金属薄膜后的能量吸收及演化过程，提出了金属薄膜/复合材料组合体系在纳秒级脉冲激光作用下，因复合材料易气化的特性而存在的特有的薄膜/基底界面分离现象。提出利用这一特有的界面分离过程，可通过控制激光能量密度实现对这种结构体系的高精度、无损伤的刻蚀。利用波前衍射变换技术整形过的刻蚀激光进行了验证实验，实验结果证实了这一方法的可行性。

By utilizing multimode squeezed states theory, we study the generalized nonlinear equal-power higher-power sum squeezing properties of the generalized magnetic-field component in four-state superposition multimode entangled state light field |\psi^{(4)}>q. The state is composed of multimode vacuum state, multimode coherent state and its contrary state, multimode imaginary coherent state. It is found that the state |\psi^{(4)}>q is a type of four-state superposition multimode nonclassical light field, and under certain fixed conditions, the generalized magnetic-field component in the state |\psi^{(4)}>q can display generalized nonlinear equal-power 4m-th power sum squeezing effects which change periodically.