Electrocatalytic NAD⁺ reduction via hydrogen atom-coupled electron transfer

Area of Science:

• Electrochemistry
• Catalysis
• Biochemistry

Background:

• Nicotinamide adenine dinucleotide cofactor (NAD(P)H) is crucial for energy transfer and charge mediation.
• Natural photosynthesis uses hydride transfer for NADPH production.
• Artificial NAD(P)H regeneration faces challenges with byproduct formation.

Purpose of the Study:

• To investigate electrocatalytic NADH regeneration mechanisms on various electrodes.
• To understand factors influencing selectivity and byproduct formation.
• To compare electrocatalytic mechanisms with biocatalysis.

Main Methods:

• Electrocatalytic NADH regeneration experiments on Cu, Fe, Co, and carbon electrodes.
• Analysis of reaction products, including NAD2 and ADP-ribose.
• H/D isotope effects and electron paramagnetic resonance (EPR) spectroscopy to elucidate reaction mechanisms.

Main Results:

• High selectivity for 1,4-NADH regeneration observed on Cu, Fe, and Co electrodes, with minimal NAD2 byproduct.
• Carbon electrodes produced significantly more NAD2 byproduct.
• ADP-ribose identified as a byproduct from NAD+ fragmentation.
• A hydrogen atom-coupled electron transfer (HAdCET) mechanism proposed for metal electrodes.
• A direct electron transfer and NAD radical pathway implicated for carbon electrodes.

Conclusions:

• Electrocatalytic NADH regeneration on metal electrodes offers higher selectivity compared to carbon electrodes.
• The HAdCET mechanism on metal surfaces explains the reduced byproduct formation.
• This study reveals a distinct mechanism for electrocatalytic NADH regeneration compared to natural biocatalysis.