Faid Alaa Y, Barnett Alejandro Oyarce, Seland Frode, Sunde Svein
Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7491, Trondheim, Norway.
SINTEF Industry, New Energy Solutions Department, 7465, Trondheim, Norway.
ACS Appl Energy Mater. 2021 Apr 26;4(4):3327-3340. doi: 10.1021/acsaem.0c03072. Epub 2021 Mar 23.
Tailoring catalyst-ionomer and electrolyte interaction is crucial for the development of anion exchange membrane (AEM) water electrolysis. In this work, the interaction of Ni-MoO nanosheets with ionomers and electrolyte cations was investigated. The activity of Ni-MoO nanosheets for the hydrogen evolution reaction (HER) increased when tested in 1 M NaOH compared to 1 M KOH; however, it decreased when tested in 0.01 M KOH compared to 1 M KOH electrolyte. The capacitance minimum associated with the potential of zero free charge (pzfc) was shifted negatively from 0.5 to 0.4 V versus RHE when KOH concentration increased from 0.1 mM to 1 M KOH, suggesting a softening of the water in the double-layer to facilitate the OH transport and faster kinetics of the Volmer step that lead to improved HER activity. The catalyst interaction with cationic moieties in the anion ionomer (or organic electrolytes) can also be rationalized based on the capacitance minimum, because the latter indicates a negatively charged catalyst during the HER, attracting the cationic moieties leading to the blocking of the catalytic sites and lower HER performance. The HER activity of Ni-MoO nanosheets is lower in benzyltrimethylammonium hydroxide (BTMAOH) than in tetramethylammonium hydroxide (TMAOH). Anion fumion ionomer and electrolytes with organic cations with benzyl group adsorption (such as BTMAOH) lead to decreased HER activity in comparison with TMAOH and Nafion. By utilizing Ni-MoO nanosheet electrodes as a cathode in a full non-platinum group metal (PGM) AEM electrolyzer, a current density of 1.15 A/cm at 2 V cell voltage in 1 M KOH at 50 °C was achieved. The electrolyzer showed exceptional stability in 0.1 M KOH for 65 h at 0.5 A/cm.
调整催化剂-离聚物与电解质之间的相互作用对于阴离子交换膜（AEM）水电解的发展至关重要。在这项工作中，研究了Ni-MoO纳米片与离聚物和电解质阳离子之间的相互作用。与在1 M KOH中测试相比，在1 M NaOH中测试时，Ni-MoO纳米片对析氢反应（HER）的活性有所增加；然而，与在1 M KOH电解质中测试相比，在0.01 M KOH中测试时其活性降低。当KOH浓度从0.1 mM增加到1 M KOH时，与零自由电荷电位（pzfc）相关的电容最小值相对于可逆氢电极（RHE）从0.5 V负移至0.4 V，这表明双层中的水软化，有利于OH传输以及Volmer步骤的更快动力学，从而提高了HER活性。基于电容最小值，也可以解释催化剂与阴离子离聚物（或有机电解质）中阳离子部分的相互作用，因为后者表明在HER过程中催化剂带负电荷，吸引阳离子部分，导致催化位点被阻断，HER性能降低。Ni-MoO纳米片在苄基三甲基氢氧化铵（BTMAOH）中的HER活性低于在四甲基氢氧化铵（TMAOH）中的活性。与TMAOH和Nafion相比，具有苄基吸附的有机阳离子的阴离子离聚物和电解质（如BTMAOH）会导致HER活性降低。通过在全非铂族金属（PGM）AEM电解槽中使用Ni-MoO纳米片电极作为阴极，在50℃下的1 M KOH中，在2 V电池电压下实现了1.15 A/cm²的电流密度。该电解槽在0.1 M KOH中于0.5 A/cm²下表现出65小时的出色稳定性。
