Electrochemical reduction of CO2 provides an ideal approach to convert the greenhouse gas into fuels under mild conditions. Copper electrodes are capable of producing significant amounts of hydrocarbons, but the selectivity to convert CO2 into methane (CH4) remains low. Here, we prepared functionalized Cu nanowire electrodes by coating polymers (polydopamine, PDA) and experimentally verified that the functionalized CuNWs indeed shows 2.3 times higher CH4 selectivity compared with that of CuNWs. The PDA functionalized CuNWs catalyst remains catalytically stable for in excess of 14 hours. We experimentally reveal that the amino groups could be responsible for the capture and delivery of protons for the hydronation of CO* intermediates and phenolic hydroxyl groups for the stabilization of CO* intermediates. The results provide us insights into a new approach to optimize the electrochemical methanation of CO2 by polymers that contain abundant functional groups.

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During the switching on/off of shunt capacitor banks in substations, vacuum circuit breakers (VCBs) are required to switch off or to switch on the capacitive current. Therefore, the VCBs have to be operated under a harsh condition to ensure the reliability of the equipment. This study presents a complete comparison study of ordinary and phase-controlled VCBs on switching 10 kV shunt capacitor banks. An analytical analysis for switching 10 kV shunt capacitor banks is presented on the basis of a reduced circuit with an ungrounded neutral. A phase selection strategy for VCBs to switch 10 kV shunt capacitor banks is proposed. Switching on current waveforms and switching off overvoltage waveforms with, and without, phase selection were measured and discussed by field experiments in a 110 kV substation in Chongqing, China. Results show that the operation of phase-controlled VCBs for 10 kV switching shunt capacitor banks is stable, and phase-controlled VCBs can be used to implement the 10 kV switching on/off shunt capacitor banks to limit the transient overvoltage and overcurrent. The values of overvoltage and inrush current using phase-controlled VCBs are all below those with ordinary VCBs.