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N-doped carbon nanostructures have been widely employed as high-performance electrocatalysts for water-splitting reactions. Particularly, the development of N‐doped graphene and N‐doped carbon nanotubes has sparked a lot of
interest in recent years in the material science community. In this direction, Junji
Nakamura and coworkers, through a seminal work, have elucidated, after a long
period of controversy, the mechanism of the oxygen reduction reaction (ORR) in
N-doped carbon materials. They discovered that pyridinic N can generate carbon
atoms with Lewis basicity, which leads to the adsorption of O 2 molecules onto
them at the first step of oxygen electroreduction [27, 28]. Finding new avenues to
synthesize metal-free electrocatalysts, proteins have been used as a N-source to
create very promising N-doped carbon nanocatalysts due to the significant contents of pyrrolic N, pyridinic N and amine groups in their molecular architectures. Among the most significant contributions found is the covalent attachment
of hemoglobin to fructose-functionalized graphene oxide nanostructures to built
high-performance ORR electrocatalysts [6]. Through an elegant and pioneering
work, Santiago and coworkers have developed a methodology to multiply the
electrocatalytic activity of graphene-oxide nanoplatforms through the unfolding
of adsorbed hemoglobin molecules using fructose linkers as denaturing agents.
During the denaturalization process, the proteins adopt a fibrin-like structure,
releasing almost all their redox-active centers and exposing their pyridine groups
to electrochemical interfaces. The fixed hemoglobins significantly boosted the
ORR properties of the graphene oxide nanoplatforms in terms of onset potential
and current density. This work paved the way towards the development of metalfree nanobioelectrocatalysts.
Inspired by nature, Compton and coworkers developed a revolutionary methodology to amplify the ORR bioelectrocatalytic signal of redox proteins using layered
structured films composed of conductive polymers and hemoglobin molecules in a
sandwich-like configuration [29]. The synergistic interactions between Nafion and
hemoglobin gave rise to the full conversion of oxygen to water by a four-electron
pathway of the water-splitting process, which, in turn, boosted electrocatalytic
activity.
Redox enzymes possess myriad different types of redox sites, including hemes,
chlorins, quinones, favins, Fe–S clusters, tyrosine and tryptophan residues, copper, molybdenum, and manganese ions, which can catalyze a large portfolio of
redox reactions based on their electron-transporting properties and structural affinity for the reactant molecules [30–34]. Remarkably, they could be easily integrated
into different types of nanoplatforms to significantly boost their electrocatalytic
performances.
In this review, we provide a timely summary of recent methodologies developed
to fabricated high-performance protein-based nanoelectrocatalysts for water-splitting reactions. We describe the relationship between the structural properties of the
nanobiomaterials and their electrocatalytic performances based on an understanding of the reaction mechanisms and the role of the biomolecule structure. Additionally, we envision the development of molecular biocatalytic nitrogen reduction reaction (NRR) nanomaterials for the efficient electrochemical production under mild
conditions of ammonia, which is used as a refrigerant gas, for purification of water
239
Reprinted from the journal
Topics in Current Chemistry (2020) 378:43
N-doped carbon nanostructures have been widely employed as high-performance electrocatalysts for water-splitting reactions. Particularly, the development of N‐doped graphene and N‐doped carbon nanotubes has sparked a lot of
interest in recent years in the material science community. In this direction, Junji
Nakamura and coworkers, through a seminal work, have elucidated, after a long
period of controversy, the mechanism of the oxygen reduction reaction (ORR) in
N-doped carbon materials. They discovered that pyridinic N can generate carbon
atoms with Lewis basicity, which leads to the adsorption of O 2 molecules onto
them at the first step of oxygen electroreduction [27, 28]. Finding new avenues to
synthesize metal-free electrocatalysts, proteins have been used as a N-source to
create very promising N-doped carbon nanocatalysts due to the significant contents of pyrrolic N, pyridinic N and amine groups in their molecular architectures. Among the most significant contributions found is the covalent attachment
of hemoglobin to fructose-functionalized graphene oxide nanostructures to built
high-performance ORR electrocatalysts [6]. Through an elegant and pioneering
work, Santiago and coworkers have developed a methodology to multiply the
electrocatalytic activity of graphene-oxide nanoplatforms through the unfolding
of adsorbed hemoglobin molecules using fructose linkers as denaturing agents.
During the denaturalization process, the proteins adopt a fibrin-like structure,
releasing almost all their redox-active centers and exposing their pyridine groups
to electrochemical interfaces. The fixed hemoglobins significantly boosted the
ORR properties of the graphene oxide nanoplatforms in terms of onset potential
and current density. This work paved the way towards the development of metalfree nanobioelectrocatalysts.
Inspired by nature, Compton and coworkers developed a revolutionary methodology to amplify the ORR bioelectrocatalytic signal of redox proteins using layered
structured films composed of conductive polymers and hemoglobin molecules in a
sandwich-like configuration [29]. The synergistic interactions between Nafion and
hemoglobin gave rise to the full conversion of oxygen to water by a four-electron
pathway of the water-splitting process, which, in turn, boosted electrocatalytic
activity.
Redox enzymes possess myriad different types of redox sites, including hemes,
chlorins, quinones, favins, Fe–S clusters, tyrosine and tryptophan residues, copper, molybdenum, and manganese ions, which can catalyze a large portfolio of
redox reactions based on their electron-transporting properties and structural affinity for the reactant molecules [30–34]. Remarkably, they could be easily integrated
into different types of nanoplatforms to significantly boost their electrocatalytic
performances.
In this review, we provide a timely summary of recent methodologies developed
to fabricated high-performance protein-based nanoelectrocatalysts for water-splitting reactions. We describe the relationship between the structural properties of the
nanobiomaterials and their electrocatalytic performances based on an understanding of the reaction mechanisms and the role of the biomolecule structure. Additionally, we envision the development of molecular biocatalytic nitrogen reduction reaction (NRR) nanomaterials for the efficient electrochemical production under mild
conditions of ammonia, which is used as a refrigerant gas, for purification of water
239
Reprinted from the journal
Topics in Current Chemistry (2020) 378:43