Hydrophilic/Aerophobic Hydrogen-Evolving Electrode: NiRu-Based Metal–Organic Framework Nanosheets In Situ Grown on Conductive Substrates

Abstract

Electrocatalytic reduction of water via hydrogen evolution reaction (HER) is considered one of the most ideal avenues to produce high-purity hydrogen (H 2 ) in large quantities, which always requires active electrocatalysts to overcome the high energy barrier. It is of significance yet challenging to design and construct effective HER electrocatalysts of an acceptable cost. In this study, a highly efficient metal−organic framework (MOF)-based electrochemical HER system based on NiRu-based binary MOF (Ru-doped Ni 2 (BDC) 2 TED MOF, BDC = 1,4-benzenedicarboxylic acid; TED = triethylenediamine) nanosheets grown on conductive substrates (e.g., Ni foam, carbon cloth) is fabricated by a facile solvothermal method. The resultant NiRu-MOF-based composites possess enhanced electron transport ability and water stability, accompanied by increased electrochemically active areas and hydrophilic/aerophobic properties. With these advantages, the optimized NiRu-MOF nanosheet arrays on Ni foam substrate (NiRu-MOF/NF) with a Ru/Ni molar ratio of 6/94 in the MOF structure could exhibit efficient catalytic performance for HER in alkaline conditions, requiring a small overpotential of 51 mV at −10 mA cm −2 . This study could provide a feasible way for the design and synthesis of two-dimensional (2D) MOF-based materials with controllable interface properties for energy catalysis and beyond.

Avoiding Pyrolysis and Calcination: Advances in the Benign Routes Leading to MOF‐Derived Electrocatalysts

“…The HER activity was finally investigated in a 1 M KOH solution and compared to that of a commercial platinum on carbon catalyst (Pt/C) (Figure 6d). [73] The polarization curve of the NiRu-MOF film shows lower current densities compared to Pt/C, at overpotentials lower than 190 mV. Interestingly, this trend reverses at overpotentials > 200 mV and the MOF outperforms the Pt/C catalyst.…”

“…However, the high prices due to the limited availability of Pt make their replacement with cheaper substitutes very attractive. MOFs and their derivatives received significant attention as HER catalyst in the last decade [73] …”

“…This can generally increase the electrochemically active surface area (ECSA) as a larger part of the surface can get wet with the electrolyte. The HER activity was finally investigated in a 1 M KOH solution and compared to that of a commercial platinum on carbon catalyst (Pt/C) (Figure 6d) [73] …”

“…Tafel slope was determined as 90 mV dec À 1 , which led the authors to conclude that the reaction proceeds via the Volmer Heyrovsky mechanism. [73] In fact, the slope suggests that the Volmer mechanism is limiting. However, the situation is too complex to show without further measurements that the Heyrovsky mechanism occurs without contributions from the Tafel mechanism.…”

“…In some cases, MOFs can also find direct use, upon deposition, as HER catalysts. For example, Y. Xu and co‐workers recently prepared a highly active NiRu‐based binary MOF: Ru‐doped Ni 2 (BDC) 2 TED MOF on a nickel foam and carbon cloth substrate (H 2 BDC: 1,4‐benzenedicarboxylic acid or terephthalic acid) [73] . This MOF was synthesized using a facile solvothermal method.…”