設計された欠陥/活性部位を有する金属酸化物を使った酵素的乳酸生成のための活性補酵素1,4-NADHの電気化学的生成

概要

九州大学学術情報リポジトリ
Kyushu University Institutional Repository

Electrochemical generation of active coenzyme
1,4-NADH for enzymatic lactic acid production
on metal oxides with engineered defects/active
sites
ナダ フッシェン アミン モハメド ベシサ

https://hdl.handle.net/2324/7157289
出版情報：Kyushu University, 2023, 博士（理学）, 課程博士
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（様式３）

氏
論

：Nada Hussien Amin Mohamed Besisa

名

名：Electrochemical generation of active coenzyme 1,4-NADH for enzymatic lactic

文

acid

production on metal oxides with engineered defects/active sites

(設計された欠陥/活性部位を有する金属酸化物を使った酵素的乳酸生成のための
活性補酵素 1,4-NADH の電気化学的生成)

区

分

：

甲
論

文

内

容

の

要

旨

Nicotinamide adenine dinucleotide and its hydride (NAD＋ and NADH) are key chemicals for
enhancing energy and material conversions under mild conditions in various systems. Recently,
transition-metal oxides have received much attention due to their abundance, non-toxicity, good
stability, and high activity in various applications. The aim of this study is the enhancement
electrochemical generation of the enzymatically active coenzyme nicotinamide adenine
dinucleotide (1,4-NADH) using different materials, focusing mainly on transition-metals oxides
for the enzymatic electrochemical production of lactic acid.
Chapter1：General Introduction
Enzymatic electrochemical production of L-lactic acid offers several advantages over
traditional chemical methods. It operates under mild reaction conditions, minimizing energy
consumption and reducing the need for harsh chemicals. Electrochemistry is employed to
provide the necessary driving force for the reaction and to enhance the overall efficiency of the
process. The overpotential for the electrochemical generation of the cofactor NADH besides the
unaffordable electrode materials are the most critical bottleneck. Therefore, providing practical
and affordable solution is highly demanded.
Chapter2 ： Electrochemical regeneration of 1,4-NADH on Ptn+- enhanced TiO2/Ti and its
application for enzymatic electrochemical production of lactic acid
TiO2 is one of the well-known oxides in many applications specially in electrochemistry.
Moreover, TiO2 showed high
selectivity
efficiency

and
for

Faradaic

production

of

several valuable products owing
to its interaction with organic
molecules. The author prepared
TiO2 electrochatalyst grown on
Ti

electrode

(TOT)

Pt

Fig.1. (a) TEM image of Pt-TOT.2 (b) yield% of 1,4-NADH generation on TOT,

enhanced TOT with different Pt

Pt, Pt-TOT.2, and (c) schematic mechanism of electrochemical reduction of

content

NAD for enzymatic electrochemical production of lactic acid on Pt-TOTs.

(Pt-TOT.X,

and
X

has

+

numbers from 1 up to 4 accordingly with increasing Pt content from ≈ 2 to 8 Atom.%) were
prepared via one step process. TEM showed that Pt particles with high contrast form on the
surface of TOT grains and a part of grain also has higher contrast (Fig. 1a). By optimizing the
loading amount of Pt, the author achieved 90% generation (yield) of 1,4-NADH using Pt-TOT at
the lowest potentials through the reported electrodes (–0.6V vs Ag/AgCl) and up to 100% at only
–0.8V vs Ag/AgCl (as shown in Fig.1b). The remarkable performance of our best electrode PtTOT was brought by cooperation of predominant adsorption of NADs on TiO2 and fast kinetics
in hydrogenation realized on Pt-TOT including Ptn+ species taking various valence states (Fig.
1c). The electrochemically generated NADH was directly applicated to enzymatic lactic acid
formation from pyruvic acid using a lactate dehydrogenase (LDH).
Chapter3：Application of perovskite oxides for electrochemical regeneration of 1,4-NADH
The ABO3 compounds hold a special interest due to their tunable structure and the
discovery of new materials with interesting and technologically enabling target functionalities.
The main objective of this study is to test perovskite oxides with stability and improved
electronic transport properties for the electrochemical generation of NADH.
The prepared oxides at higher temperature gave higher yield. Among the three perovskite oxides
CaMnO3(CMO) achieved the highest yield over 90% for the generation of the active 1,4-NADH
at –0.8 V vs Ag/AgCl (Fig. 2a), as well as the highest conversion rate of NAD+ and selectivity for
1,4-NADH.
Chapter4：Controlling parameters and engineering of active sites of TiO2/Ti and Ni-TiO2/Ti
electrodes for electrochemical reduction of NAD+
In this chapter, TiO2 with different thickness and structure was grown on Ti mesh. Ni
nanoparticles were then loaded with different amounts on the best performing TOT, and
reduction treatment assisted by hydrogen spillover was subsequently used to form more active
sites. The samples were designated Ni-TOT.2-1 with 10 cycles of Ni electrodeposition, Ni-TOT.22 with 40 cycles of Ni electrodeposition, with 10 cycles of Ni electrodeposition and hydrogen
treatment (Ni-TOT.2-H), and Ni-TOT.2-2H with 40 cycles of Ni electrodeposition and hydrogen
treatment. X-ray photoemission specroscopy (XPS) suggested that oxidation states of Ti species
included in the prepared catalysts depend on
the treatment conditions (Fig. 2.a). Ni-TOT.22H exhibited the highest yield of 59±2% at
only –0.8 V vs Ag/AgCl and a higher yield of
93.8±1.4% at a slightly higher potential of –
0.9 v vs Ag/AgCl (Fig.2. b). The catalytic
activity

of

these

electrodes

is

strongly

modified by the presence of active sites,
including Ti3+ and oxygen vacancies (Fig.
2.a), which act as adsorption sites for
and

then

facilitate

the

NAD+

selective

Fig. 2. (a) XPS spectra of Ti 2p, and (b) Yield% of 1,4-NADH
regeneration conducted on Ni-TOT.s at low potentials.

hydrogenation by adsorbed H on Ni loaded particles.

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