Effect of Surface Ligands on CoP for the Hydrogen Evolution Reaction

Abstract

The activity of colloidally synthesized CoP for the hydrogen evolution reaction (HER) was studied to determine the impact of surface ligands on catalysis. The as-synthesized CoP nanocrystals were stripped with trialkyloxonium tetrafluoroborate (Meerwein’s reagent) to create a “blank template” that was then re-ligated with carboxylates (oleate, octanoate, acetate) and amines (oleylamine, octylamine, dioctylamine, trioctylamine butylamine). Carboxylates and amines were chosen due to their prevalence in colloidal syntheses, and the range of ligands was chosen to study the impact of sterics and hydrophobicity of the surface ligands on catalysis. Long chain carboxylates were found to result in a larger increase in overpotential when compared to the equivalent amine (e.g., oleate vs oleylamine), due to higher ligand density and stronger coordination with carboxylates. Increased carbon chain length resulted in increased overpotential with carboxylates; however, the range of 1° amines studied had similar overpotentials. This is due to the lower ligand density and therefore sparse ligand packing for the 1° amines. These results suggest that the mechanism by which surface ligands impede catalysis on CoP for HER is primarily through inhibiting substrate access to surface active sites rather than poisoning the active sites.

Metal–ligand bond strength determines the fate of organic ligands on the catalyst surface during the electrochemical CO2 reduction reaction

“…[7][8][9][10][11] Studies investigating surface chemistry in electrocatalysis are still comparatively scarce and mostly focus on the hydrogen and oxygen evolution reactions. [12][13][14][15] In general, understanding the role of organic ligands still remains of utmost importance in order to correctly interpret the structure/property relations in colloidally synthesised catalysts and to potentially design interfaces that are benecial for activity, selectivity and stability.…”

Molecular tunability of surface-functionalized metal nanocrystals for selective electrochemical CO2 reduction

“…Nevertheless, the promoting effects of tailor-made ligands on heterogeneous catalysts are boldly emerging in various reactions, ranging from catalytic organic transformations [1][2][3][4][5] to photocatalysis [6][7][8] and electrocatalysis, including the oxygen-reduction reaction (ORR) 9 and the hydrogen-evolution reaction (HER). [10][11][12] The electrochemical reduction of carbon dioxide (CO 2 RR) holds enormous potential to meet modern-day challenges in energy storage thanks to its ability to convert CO 2 into energydense and transportable hydrocarbons and alcohols. 13,14 However, in order to develop into a viable energy technology, many improvements must be made in terms of: lowering the required overpotential; increasing the catalyst activity; and directing the selectivity towards a single product.…”

Direct solvent free synthesis of bare α-NiS, β-NiS and α-β-NiS composite as excellent electrocatalysts: Effect of self-capping on supercapacitance and overall water splitting activity

“…Similarly, the use of long chain organic surfactants is known to provide better control over the size and morphology of the synthesized materials 42 . However, the presence of a significant amount of ligand/carbonaceous residue on the surface of the materials originating from the ligands has been shown to diminish materials' end application 43,44 .…”

“…The synthesis of nanomaterials via thermolytic, solvent free decomposition of single molecular precursors has been demonstrated as a simple, economical, self-capping and highly efficient route 45 . The method avoids the use of long chain capping ligands, and thus offers the possibility of synthesizing nanomaterials with abundant exposed active sites for enhanced electrocatalytic performance 43,44 . Various single source precursors such as metal thiolates, metal salts of dithiocarbamates, xanthates, thiocarboxylates and thiotetrazoles have been employed in the synthesis of a variety of nanostructured materials [45][46][47][48] .…”