Open Access Research Article Online first
Benzoate anions-intercalated NiFe-layered double hydroxide nanosheet array with enhanced stability for electrochemical seawater oxidation
Nano Research Energy
Published: 06 September 2022

Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy, but detrimental chlorine species (i.e., chloride and hypochlorite) cause severe corrosion at the anode. Here, we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth (BZ-NiFe-LDH/CC) behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation, affords enlarged interlayer spacing of LDH, inhibits chlorine (electro)chemistry, and alleviates local pH drop of the electrode. It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm–2 in 1 M KOH. In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis, BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm–2 in alkaline seawater. Operando Raman spectroscopy studies further identify structural changes of disordered δ (NiIII-O) during the seawater oxidation process.

Research Article Issue
N, O-doped carbon foam as metal-free electrocatalyst for efficient hydrogen production from seawater
Nano Research 2022, 15 (10): 8922-8927
Published: 19 August 2022

Seawater electrolysis is the most promising technology for large scale hydrogen production due to the abundance and low cost of seawater in nature. However, compared with the traditional freshwater electrolysis, the issues of electrode poisoning and corrosion will occur during the seawater electrolysis process, and active and stable electrocatalysts for the hydrogen evolution reaction (HER) are thus highly desired. In this work, N, O-doped carbon foam in-situ derived from commercial melamine foam is proposed as a high-active metal-free HER electrocatalyst for seawater splitting. In acidic seawater, our catalyst shows high hydrogen generation performance with small overpotential of 161 mV at 10 mA·cm−2, a low Tafel slop of 97.5 mV·dec−1, and outstanding stability.

Research Article Issue
CeO2 nanoparticles with oxygen vacancies decorated N-doped carbon nanorods: A highly efficient catalyst for nitrate electroreduction to ammonia
Nano Research 2022, 15 (10): 8914-8921
Published: 17 August 2022

Electrocatalytic nitrate reduction reaction (NO3RR) emerges as a highly efficient approach toward ammonia synthesis and degrading NO3 contaminant. In our study, CeO2 nanoparticles with oxygen vacancies (VO) decorated N-doped carbon nanorods on graphite paper (CeO2−x@NC/GP) were demonstrated as a highly efficient NO3RR electrocatalyst. The CeO2−x@NC/GP catalyst manifests a significant NH3 yield up to 712.75 μmol·h−1·cm−2 at −0.8 V vs. reversible hydrogen electrode (RHE) and remarkable Faradaic efficiency of 92.93% at −0.5 V vs. RHE under alkaline conditions, with excellent durability. Additionally, an assembled Zn-NO3 battery with CeO2−x@NC/GP as cathode accomplishes a high-power density of 3.44 mW·cm−2 and a large NH3 yield of 145.08 μmol·h−1·cm−2. Density functional theory results further expose the NO3 reduction mechanism on CeO2 (111) surface with VO.

Research Article Issue
Enhanced N2-to-NH3 conversion efficiency on Cu3P nanoribbon electrocatalyst
Nano Research 2022, 15 (8): 7134-7138
Published: 18 June 2022

Ambient electroreduction of nitrogen (N2) is considered as a green and feasible approach for ammonia (NH3) synthesis, which urgently demands for efficient electrocatalyst. Morphology has close relationship with catalytic activity of heterogeneous catalysts. Nanoribbon is attractive nanostructure, which possesses the flexibility of one-dimensional nanomaterials, the large surface area of two-dimensional nanomaterials, and lateral size confinement effects. In this work, Cu3P nanoribbon is proposed as a highly efficient electrocatalyst for N2-to-NH3 conversion under benign conditions. When measured in N2-saturated 0.1 M HCl, such Cu3P nanoribbon achieves high performance with an excellent Faradaic efficiency as high as 37.8% and a large yield of 18.9 µg·h−1·mgcat.−1 at −0.2 V. It also demonstrates outstanding stability in long-term electrolysis test at least for 45 h.

Open Access Review Article Issue
Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis
Nano Research Energy 2022, 1: e9120010
Published: 02 June 2022

To restore the natural nitrogen cycle (N-cycle), artificial N-cycle electrocatalysis with flexibility, sustainability, and compatibility can convert intermittent renewable energy (e.g., wind) to harmful or value-added chemicals with minimal carbon emissions. The background of such N-cycles, such as nitrogen fixation, ammonia oxidation, and nitrate reduction, is briefly introduced here. The discussion of emerging nanostructures in various conversion reactions is focused on the architecture/compositional design, electrochemical performances, reaction mechanisms, and instructive tests. Energy device advancements for achieving more functions as well as in situ/operando characterizations toward understanding key steps are also highlighted. Furthermore, some recently proposed reactions as well as less discussed C–N coupling reactions are also summarized. We classify inorganic nitrogen sources that convert to each other under an applied voltage into three types, namely, abundant nitrogen, toxic nitrate (nitrite), and nitrogen oxides, and useful compounds such as ammonia, hydrazine, and hydroxylamine, with the goal of providing more critical insights into strategies to facilitate the development of our circular nitrogen economy.

Research Article Issue
Rational design of eco-friendly Mn-doped nonstoichiometric CuInSe/ZnSe core/shell quantum dots for boosted photoelectrochemical efficiency
Nano Research 2022, 15 (8): 7614-7621
Published: 31 May 2022

Colloidal core/shell quantum dots (QDs) with environment-friendly feature and controllable optoelectronic properties are promising building blocks in emerging solar technologies. In this work, we rationally design and tailor the eco-friendly CuInSe (CISe)/ZnSe core/shell QDs by Mn doping and stoichiometric optimization (i.e., molar ratios of Cu/In). It is demonstrated that Mn doping in In-rich CISe/ZnSe core/shell QDs can effectively engineer the charge kinetics inside the QDs, enabling efficient photogenerated electrons transfer into the shell for retarded charge recombination. As a result, a solar-driven photoelectrochemical (PEC) device fabricated using the optimized Mn-doped In-rich CISe/ZnSe core/shell QDs (Cu/In ratio of 1/2) exhibits improved charge extraction and injection, showing a ~ 3.5-fold higher photocurrent density than that of the pristine CISe/ZnSe core/shell QDs under 1 sun AM 1.5G illumination. The findings indicate that transition metal doping in “green” nonstoichiometric core/shell QDs may offer a new strategy for achieving high-efficiency solar energy conversion applications.

Research Article Issue
Ni(OH)2 nanoparticles encapsulated in conductive nanowire array for high-performance alkaline seawater oxidation
Nano Research 2022, 15 (7): 6084-6090
Published: 21 April 2022

Design and development of high-efficiency and durable oxygen evolution reaction (OER) electrocatalysts is crucial for hydrogen production from seawater splitting. Herein, we report the in situ electrochemical conversion of a nanoarray of Ni(TCNQ)2 (TCNQ = tetracyanoquinodimethane) on graphite paper into Ni(OH)2 nanoparticles confined in a conductive TCNQ nanoarray (Ni(OH)2-TCNQ/GP) by anode oxidation. The Ni(OH)2-TCNQ/GP exhibits high OER performance and demands overpotentials of 340 and 382 mV to deliver 100 mA·cm−2 in alkaline freshwater and alkaline seawater, respectively. Meanwhile, the Ni(OH)2-TCNQ/GP also demonstrates steady long-term electrochemical durability for at least 80 h under alkaline seawater.

Research Article Issue
Bi nanoparticles/carbon nanosheet composite: A high-efficiency electrocatalyst for NO reduction to NH3
Nano Research 2022, 15 (6): 5032-5037
Published: 28 March 2022

Electrochemical reduction of NO offers us an attractive alternative to traditional selective catalytic reduction process for harmful NO removal and simultaneous NH3 production, but it requires efficient electrocatalyst to enable the NO reduction reaction with high selectivity. Here, we report on the development of Bi nanoparticles/carbon nanosheet composite (Bi@C) for highly effective NO reduction electrocatalysis toward selective NH3 formation. Such Bi@C catalyst attains an impressive NH3 yield of 1,592.5 μg·h−1·mgcat.−1 and a high Faradaic efficiency as high as 93% in 0.1 M Na2SO4 electrolyte. Additionally, it can be applied as efficient cathode materials for Zn–NO battery to reduce NO to NH3 with high electricity generation.

Research Article Issue
FeP nanorod array: A high-efficiency catalyst for electroreduction of NO to NH3 under ambient conditions
Nano Research 2022, 15 (5): 4008-4013
Published: 07 March 2022

Sustainable mitigation of the continuously rising concentration of NO contaminants is among the most urgent issues of this century. Ambient electrocatalytic conversion of NO into useful NH3 offers an attractive path toward achieving sustainable NO abatement and NH3 production simultaneously. However, its efficiency is challenged by the intense competition from hydrogen evolution reaction and relatively high energy barriers of NO activation. It is thus highly desirable to explore active electrocatalyst for NO reduction reaction and investigate the mechanisms on relevant surfaces. Herein, we introduce an FeP nanorod array on carbon cloth as a high-efficiency catalyst for NO electroreduction to NH3. In 0.2 M phosphate-buffered solution, this catalyst exhibits a low onset potential of −0.014 V. Moreover, it achieves a remarkable Faradaic efficiency of 88.49% and a large NH3 yield of 85.62 μmol·h−1·cm−2, with durability for stable NO conversion over 12 h of electrolysis. The catalytic mechanism on FeP is investigated further by theoretical calculations.

Research Article Issue
Highly efficient two-electron electroreduction of oxygen into hydrogen peroxide over Cu-doped TiO2
Nano Research 2022, 15 (5): 3880-3885
Published: 11 January 2022

Electrosynthesis of hydrogen peroxide (H2O2), as a sustainable alternative to the anthraquinone oxidation method, provides the feasibility of directly generating H2O2. Here, we report Cu-doped TiO2 as an efficient electrocatalyst which exhibits the excellent two-electron oxygen reduction reaction (2e ORR) performance with respect to the pristine TiO2. The Cu doping results in the distortion of TiO2 lattice and further forms a large number of oxygen vacancies and Ti3+. Such Cu-doped TiO2 exhibits a positive onset potential about 0.79 V and high H2O2 selectivity about 91.2%. Moreover, it also shows a larger H2O2 yield and good stability. Density functional theory (DFT) calculations reveal that Cu dopant not only improves the electrical conductivity of pristine TiO2 but reduces the *OOH adsorption energy of active sites, which is beneficial to promote subsequently 2e ORR process.

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