Electrocatalytic Hydrogen Evolution using a Nickel-based Calixpyrrole Complex: Controlling the Secondary Coordination...

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Designing advanced electrocatalysts is crucial for efficient energy conversion.
• Integrating microenvironment control into active sites offers a promising strategy for catalyst development.

Purpose of the Study:

• To develop a novel heterogeneous catalyst for hydrogen evolution.
• To investigate the role of pendant amine groups in controlling the catalyst's microenvironment and reaction mechanism.

Main Methods:

• Synthesis and characterization of a square planar nickel calixpyrrole complex (Ni(DPMDA)).
• Electrocatalytic testing for hydrogen evolution reaction using anilinium tetrafluoroborate as a proton source.
• Kinetic isotope effect (KIE) studies and Tafel slope analysis to elucidate the reaction mechanism.

Main Results:

• The supported Ni(DPMDA) catalyst demonstrated remarkable stability and high turnover frequencies (TOF) up to 25,900 s⁻¹.
• Kinetic studies indicated a proton-coupled electron transfer (PCET) process involving pendant amine groups as the rate-limiting step.
• Evidence of outer-sphere reduction was observed, with pendant amines hypothesized to enhance catalytic performance.

Conclusions:

• The study presents a well-defined nickel calixpyrrole complex as a highly active and stable hydrogen evolution electrocatalyst.
• Pendant amine groups effectively control the secondary coordination sphere, facilitating a PCET mechanism and high catalytic efficiency.
• The findings offer insights into heterogeneous catalyst design for improved energy conversion reactions.