Photoelectrochemical reduction of CO2 using a TiO2 photoanode and a gas diffusion electrode modified with a metal phthalocyanine catalyst
Photoelectrochemical reduction of CO2 using a TiO2 photoanode and a gas diffusion electrode modified with a metal phthalocyanine catalyst
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DOI：
10.1016/j.electacta.2020.135805
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发表时间：
2020-01
影响因子：
6.6
通讯作者：
Katsuichiro Kobayashi;S. Lou;Yoshiyuki Takatsuji;T. Haruyama;Y. Shimizu;T. Ohno
中科院分区：
文献类型：
--
作者：
Katsuichiro Kobayashi;S. Lou;Yoshiyuki Takatsuji;T. Haruyama;Y. Shimizu;T. Ohno
经典氢电池在二氧化碳电化学还原反应(CO2RR)中遇到的传质限制促使了对气体扩散电极(GDE)系统的研究。然而，目前关于CO2RR的报告需要较大的偏置(阳极电位与阴极电位之比)才能获得高电流效率。在这项工作中，我们将二氧化钛光阳极与钴、镍或锡金属酞菁(MPC)催化剂修饰的GDE相结合，以降低对CO2RR的外部偏置要求。结果表明：(1)金属阳离子(Ni、Co或Sn2+)与酞菁配位，(2)电解液的温度和浓度以及(3)外加偏压的大小都会影响法拉第效率和产物的选择性。此外，对TiO2光阳极和MPC-GDE之间的电压分布的分析表明，TiO2/MPC-GDE电池的电流效率主要受到TiO2层过厚导致的高欧姆极化损耗的限制。MPC-GDE的阴极过程受电极活化能的控制。随后对二氧化钛光阳极厚度进行了优化，以获得更高的电流效率。当使用NiPC催化剂作为CO2RR催化剂时，PEC CO2RR的法拉第效率最高，最佳电池条件为：(I)GDE电解液温度为<；11°C；(Ii)GDE电解液浓度为>；1：MAQ。使用这些优化的电池条件，在紫外光照射下，所制备的二氧化钛/NiPC-GDE电池表现出显著的高CO2RR法拉第效率和CO的选择性(98%)，最低电池偏压为0.8nV(阳极电位与阴极电位)。这项工作提高了对基于二氧化钛/MPC-GDE光电化学体系的气相供给CO2RR反应器的电池设计的理解。
The mass transport limitations encountered in classical H-cells for electrochemical CO2reduction reaction (CO2RR) have spurred research in gas diffusion electrode (GDE) systems. However, current reports on CO2RR required large biases (anode potential vs. cathode potential > -2.0 V) for high current efficiencies. In this work, we combined a TiO2photoanode and a GDE modified with a Co, Ni or Sn metal phthalocyanine (MPc) catalyst to reduce the external bias requirement for CO2RR. We found the Faradaic efficiencies and the selectivity of the photoelectrolysis products were influenced by (i) the metal cation (Ni, Co or Sn) coordinated to the phthalocyanine, (ii) the electrolyte temperature and concentration and (iii) the magnitude of the applied bias. In addition, analyzes of the voltage distributions between the TiO2photoanode and the MPc-GDE revealed the current efficiency of the TiO2/MPc-GDE cell was limited predominantly by a high ohmic polarization loss at the TiO2photoanode due to an excessive thickness of the TiO2layer. The cathodic process at the MPc-GDE was governed by the activation energy of the electrode. The thickness of the TiO2photoanode was subsequently optimized for higher current efficiency. The highest Faradaic efficiency for PEC CO2RR was obtained when a NiPc catalyst was utilized as the CO2RR catalyst and the optimum cell conditions were as follows: (i) a GDE electrolyte temperature of <11 °C, (ii) a GDE electrolyte concentration of >1 M aq. Na2SO4electrolyte solution and (iii) a TiO2oxidation time of 3 h. Using these optimized cell conditions and under UV illumination, the as-prepared TiO2/NiPc-GDE cell shows a notably high CO2RR Faradaic efficiency and selectivity for CO (at 98%) and at a lowest reported cell bias of 0.8 V (anode potential vs cathode potential). This work provides an improved understanding of the cell designs of a vapor-fed CO2RR reactor based on a TiO2/MPc-GDE photoelectrochemical system.