Tian-Wen Jiang,Ya-Wei Zhou,Xian-Yin Ma,Xianxian Qin,Hong Li,Chen Ding,Bei Jiang,Kun Jiang,Wen-Bin Cai
The electrochemical CO2 reduction reaction (CO2RR) on Pd-based electrodes to dissolved formate and/or gaseous CO is largely dependent on potential and the electrode material, yet there is a lack of molecular-level insights into this dependence. Herein, in situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) in conjunction with differential electrochemical mass spectrometry (DEMS), gas chromatography (GC), and nuclear magnetic resonance (NMR) measurements is applied to investigate the CO2RR on Pd and Pd-B film electrodes, providing a direct observation of the role of surface CO as well as the B-doping effect at varied potentials. Comprehensive spectrometric results reveal that at lower overpotentials, CO gradually accumulates on both Pd electrode surfaces poisoning the dominant formate pathway, while at higher overpotentials, surface CO forms facilely with linearly bonded CO (the minor surface CO species) acting as an active precursor and bridge-bonded CO (the major surface CO species) as a spectator toward the gaseous CO product. Moreover, B-doping in Pd hinders CO formation and promotes formate production on the Pd-B electrode for the CO2RR as compared to that on the pristine Pd electrode at all of the overpotentials under investigation.
In order to improve the metal utilization of the noble metal Pd and the catalytic activity of the reaction, a novel and efficient Pd/Ti 4 O 7 /Ti electrode was prepared by introducing a Ti 4 O 7 intermediate layer for electrocatalytic hydrodechlorination (EHDC) of chlorinated pharmaceuticals and personal care products (PPCPs). The presence of oxygen vacancies (Ov) on the Ti 4 O 7 surface was confirmed by electron paramagnetic resonance (EPR). The results showed that the introduction of Ti 4 O 7 increased the electrochemical active surface area electrode (ECSA) of the Pd/Ti 4 O 7 /Ti electrode, accelerated the electron transfer rate on the catalyst surface, and promoted the generation of electron-rich Pd, which in turn improved the dechlorination efficiency. The Pd/Ti 4 O 7 /Ti electrode had a removal efficiency of 99.6% for florfenicol (FLO) within 180 min. Meanwhile, the removal efficiency of the Pd/Ti 4 O 7 /Ti electrode was still above 95% in seven cycles, which significantly improved the catalytic activity and stability compared with that of the Pd/Ti electrode. In addition, the reaction pathway for the electrocatalytic hydrodechlorination process of FLO at Pd/Ti 4 O 7 /Ti electrode was proposed. The ecotoxicity of the pollutants was also evaluated by the Toxicity Estimation Software Tool (T.E.S.T) model. In this study, an efficient electrocatalyst for EHDC was explored, and the Pd/Ti 4 O 7 /Ti electrode provided strong support for pollutant removal.
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