Electrocatalytic Properties of Binuclear Cu(II) Fused Porphyrins for Hydrogen Evolution

• Published in: ACS catalysis Vol. 8; no. 10; pp. 9888 - 9898
• Main Authors: Khusnutdinova, Diana, Wadsworth, Brian L, Flores, Marco, Beiler, Anna M, Reyes Cruz, Edgar A, Zenkov, Yegor, Moore, Gary F
• Format: Journal Article
• Language: English
• Published: American Chemical Society 05.10.2018
• Subjects: artificial photosynthesis; catalysis; extended macrocycles; porphyrins; hydrogen evolution reaction
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.8b01776

Binuclear copper­(II) porphyrins in which two copper­(II) porphyrin macrocycles are doubly fused at the meso-beta positions are shown to be active electrocatalysts for the hydrogen evolution reaction (2H+ + 2e– → H2). Structural characterization, including use of electron paramagnetic resonance and X-ray photoelectron spectroscopies, verifies the fused species contains two copper­(II) metal centers in its resting state. In comparison to the nonfused copper­(II) porphyrin complex, the fused species is reduced at significantly less applied bias potentials (ΔE 1/2 ∼ 570 mV for the first reduction process). Electrochemical characterization in the presence of substrate protons confirms the production of hydrogen with near-unity Faradaic efficiency, and kinetic analysis shows the catalyst achieves a maximum turnover frequency above 2 000 000 s–1. The enhancement in catalytic performance over analogous nonfused copper­(II) porphyrins indicates extended macrocycles provide an advantageous structural motif and design element for preparing electrocatalysts that activate small molecules of consequence to renewable energy.