A bis(thiosemicarbazonato)‐zinc complex, an electrocatalyst for hydrogen evolution and oxidation via ligand‐assisted metal‐centered reactivity

Abstract

Based on that hydrogen energy is widely used in fuel cells, the design and research of new catalysts for both hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs) are becoming increasingly important. A new catalyst for both hydrogen evolution and oxidation, based on a zinc complex, [Zn‐ATSE]2, is designed and provided by the reaction of Zn (CH3CO2)2 with diacetyl‐2‐(4‐N‐ethyl‐3‐thiosemicarbazone)‐3‐(4‐N‐amino‐3‐thiosemicarbazone) (H2ATSE) in our group. Electrochemical investigations show that [Zn‐ATSE]2 can electro‐catalyze hydrogen evolution from acetic acid with a turnover frequency (TOF) of 64 mol H2 mol catalyst−1 h−1 under an overpotential of 914.6 mV. Moreover, [Zn‐ATSE]2 also can electro‐catalyze hydrogen oxidation with a TOF of 13.52 s−1. The results can be attributed to the hydrazine group of [Zn‐ATSE]2 that can form a ligand‐based radical species. Possible electrocatalytic cycles for H2 production and oxidation by [Zn‐ATSE]2 are afforded. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation.

Ligand-Centered Hydrogen Evolution with Ni(II) and Pd(II)DMTH

“…To quantify the acid/base properties of the complexes, p K a,MeCN measurements were obtained through spectrophotometric titration of each compound in acetonitrile. Pyridinium tetrafluoroborate (p K a,MeCN = 12.53) was chosen because the poorly coordinating BF 4 counterions minimize ion pairing effects . Titration of NiL 1 with pyridinium tetrafluoroborate produces a reversible color change from green to yellow with clean isosbestic points at 305 and 352 nm (Figure ).…”

“…Pyridinium tetrafluoroborate (pK a,MeCN = 12.53) was chosen because the poorly coordinating BF 4 counterions minimize ion pairing effects. 9 Titration of NiL 1 with pyridinium tetrafluoroborate produces a reversible color change from green to yellow with clean isosbestic points at 305 and 352 nm (Figure 2). A pK a,MeCN of 12.71 was determined for [Ni(HL 1 )] + .…”

“…Redox-active ligands are of special interest in HER because the ligand can act as an electron reservoir and facilitate two-electron activity with earth-abundant, cost-efficient, first-row transition metals in molecular catalysts. − For several years, we and others have evaluated Zn, , Cu, − Ni, − Pd, and Co , complexes with redox-active bis-thiosemicarbazone (BTSC) ligands (Figure ) as electrocatalysts for the HER. The highly modular nature of BTSCs allows tuning of ligand electronics and basicity.…”

Influence of the Reaction Conditions in the Crystal Structures of Zn(II) and Ni(II) Coordination Compounds with a Dissymmetric Bis(Thiosemicarbazone) Ligand

“…This, together with the control of protonation/deprotonation and the nature of auxiliary anions, lead to the formation of different structures such as monomers [10][11][12], dimers [13][14][15] or coordination polymers [16][17][18]. In addition to their fascinating structural properties, TSCs have a wide range of applications in different fields as catalysis [19][20][21], metal detoxification [22][23][24], metal sensing [25][26][27] or medicine [28][29][30][31].…”