Novel Carbene Anchored Molecular Catalysts for Hydrogen Evolution Reactions

Abstract

The development of low-cost molecular electrocatalysts for the HER from water remains scarce. The efficient electrocatalytic hydrogen evolution reactions (HER) with a series of sterically encumbered carbene ligated silver­(I), gold­(I) and nickel­(II) complexes established here demonstrate the potential of molecular catalyst in hydrogen production from water. Tuning the benzannulation on the coumarin-substituted N-heterocyclic carbene (NHC) ligands afforded six new silver­(I) (5–10), two new gold­(I) (11 and 12), and two reported nickel­(II) (13 and 14) NHC complexes, which differ by the steric bulk around the metal atom and the counterion. Benefiting from the desirable structure and appropriate porous morphology, complexes 6, 9, 10, and 11 exhibited significant electrocatalytic HER activity in acidic medium with an overpotential of −226.4, −445, −243 and −310 mV vs RHE, respectively, to drive a current density of 10 mA/cm2 when immobilized on glassy carbon electrode, which is analogous to that of several transition metal-based nanomaterials. The kinetic parameters such as Tafel slope value and exchange current density for the active complexes and the former observation authenticated the Volmer–Heyrovsky mechanism. Theoretical studies advocate the potential of developing novel series of carbene-ligated HER electrocatalysts based on the controlled ligand field following scalable and viable protocols.

Hydrogen Production and Degradation of Ciprofloxacin by Ag@TiO2-MoS2 Photocatalysts

“…Industrial development, together with energy shortages and overpopulation of the planet, is perhaps among the most relevant factors affecting the environment and the future sustainable development of society [1][2][3][4][5][6][7]. Serious environmental pollution problems, which are ultimately responsible for global warming, are becoming increasingly important [3].…”

“…In this regard, chemical compounds that emulate the same mechanism as nature can be a realistic alternative that allows for solving a large part of these problems [9]. Hydrogen production by electrochemical water splitting is considered a simple and sustainable method of obtaining clean hydrogen, as energy carrier, through a hydrogen evolution reaction (HER) [4,5,[10][11][12][13]. Until now, the most effective materials for catalyzing HER have been the metals of the platinum (Pt) group [5,12,14].…”

“…Hydrogen production by electrochemical water splitting is considered a simple and sustainable method of obtaining clean hydrogen, as energy carrier, through a hydrogen evolution reaction (HER) [4,5,[10][11][12][13]. Until now, the most effective materials for catalyzing HER have been the metals of the platinum (Pt) group [5,12,14]. Current research is based on developing new high-performance and cost-effective catalysts that can be easily synthesized and that reduce enormous production costs (e.g., nanoparticles and nanocrystals, transition metal chalcogenides, metal carbides or hydroxides, among others) [1,5,15].…”

“…Until now, the most effective materials for catalyzing HER have been the metals of the platinum (Pt) group [5,12,14]. Current research is based on developing new high-performance and cost-effective catalysts that can be easily synthesized and that reduce enormous production costs (e.g., nanoparticles and nanocrystals, transition metal chalcogenides, metal carbides or hydroxides, among others) [1,5,15].…”

“…In the present research we synthesized different catalysts based on silver nanoparticles on TiO 2 NWs with a rutile structure, to which MoS 2 (5,10,20 wt.%) was added. These rutile nanowire-based catalysts were also compared with other catalysts synthesized from commercial TiO 2 (TiO 2 -P25).…”