Heterointerface-Rich Ni3N/WO3 Hierarchical Nanoarrays for Efficient Glycerol Oxidation-Assisted Alkaline Hydrogen Evolution.

Glycerol oxidation-assisted water electrolysis has emerged as a cost-effective way of co-producing green hydrogen and HCOOH. Still, preparing highly selective and stable nickel-based metal electrocatalysts remains a challenge. Herein, heterostructure Ni3N/WO3 nanosheet arrays of bifunctional catalysts with large specific surface areas loaded on nickel foam (denoted as Ni3N/WO3/NF) were synthesized. This catalyst was for glycerol oxidation reaction (GOR) and hydrogen evolution reaction (HER) with excellent catalytic performance, a voltage saving of 267 mV compared to oxygen evolution reaction (OER), and a HER overpotential of 104 mV at 100 mA cm-2. The cell voltage in the assembled GOR//HER hybrid electrolysis system reaches 100 mA cm-2 at 1.50 V, 296 mV lower than the potential required for overall water splitting. This work demonstrates that replacing GOR with OER using a cost-effective and highly active Ni-based bifunctional electrocatalyst can make hybrid water electrolysis an energy-efficient, sustainable, and green strategy for hydrogen production.

Designing Efficient Non-Precious Metal Electrocatalysts for High-Performance Hydrogen Production: A Comprehensive Evaluation Strategy.

Developing abundant Earth-element and high-efficient electrocatalysts for hydrogen production is crucial in effectively reducing the cost of green hydrogen production. Herein, a strategy by comprehensively considering the computational chemical indicators for H* adsorption/desorption and dehydrogenation kinetics to evaluate the hydrogen evolution performance of electrocatalysts is proposed. Guided by the proposed strategy, a series of catalysts are constructed through a dual transition metal doping strategy. Density Functional Theory (DFT) calculations and experimental chemistry demonstrate that cobalt-vanadium co-doped Ni3N is an exceptionally ideal catalyst for hydrogen production from electrolyzed alkaline water. Specifically, Co,V-Ni3N requires only 10 and 41 mV in alkaline electrolytes and alkaline seawater, respectively, to achieve a hydrogen evolution current density of 10 mA cm-2. Moreover, it can operate steadily at a large industrial current density of 500 mA cm-2 for extended periods. Importantly, this evaluation strategy is extended to single-metal-doped Ni3N and found that it still exhibits significant universality. This study not only presents an efficient non-precious metal-based electrocatalyst for water/seawater electrolysis but also provides a significant strategy for the design of high-performance catalysts of electrolyzed water.

Modulating adsorption energy on nickel nitride-supported ruthenium nanoparticles through in-situ electrochemical activation for urea-assisted alkaline hydrogen production.

The rational design of electrocatalysts with exceptional performance and durability for hydrogen production in alkaline medium is a formidable challenge. In this study, we have developed in-situ activated ruthenium nanoparticles dispersed on Ni3N nanosheets, forming a bifunctional electrocatalyst for hydrogen evolution and urea oxidation. The results of experimental analysis and theoretical calculations reveal that the enhanced hydrogen evolution reaction (HER) performance of O-Ru-Ni3N stems primarily from the optimized hydrogen adsorption and hydroxyl adsorption on Ru sites. The O-Ru-Ni3N on nickel foam (NF) electrode exhibits excellent HER performance, requiring only 29 mV to reach 10 mA cm-2 in an alkaline medium. Notably, when this O-Ru-Ni3N/NF catalyst is employed for both HER and urea oxidation reaction (UOR) to create an integrated H2 production system, a current density of 50 mA cm-2 can be generated at the cell voltage of 1.41 V. This report introduces an energy-efficient catalyst for hydrogen production and proposes a viable strategy for anodic activation in energy chemistry.

Kirkendall effect Strengthened-Superhydrophilic/superaerophobic Co-Ni3N/NF heterostructure as electrode catalyst for High-current hydrogen production.

The development of efficient electrocatalysts for large-scale water electrolysis is crucial and challenging. Research efforts towards interface engineering and electronic structure modulation can be leveraged to enhance the electrochemical performance of the developed catalysts. In this work, a surface-engineered Co-Ni3N/NF heterostructure electrode was prepared based on Kirkendall effect for high-current water electrolysis. In the experiments, the textural feature and intrinsic activity of the Co-Ni3N/NF heterostructure were tuned through cobalt-doping and the creation of structural defects. As a result, the increased surface energy endowed Co-Ni3N/NF heterostructure with superhydrophilic and superaerophobic properties. Meanwhile, the contact area of the gas-liquid-solid three phases was optimized. With a large underwater bubble contact angle (CA) of 169°, the electrolyte solution can infiltrate the Co-Ni3N/NF electrode within 150 ms. Sequentially, the generated gas bubbles were able to detach at high frequency, which ensured the rapid mass exchange. The performance tests showed that the optimal Co-Ni3N/NF electrode sample reached current densities of 100 mA cm-2 and 500 mA cm-2 at the overpotentials of 98 mV and 123 mV, respectively. Benefiting from the reduction of hydrogen embrittlement, the HER performance of the prepared Co-Ni3N/NF electrode sample decreased slightly after 100 h durability test, but the overall structure remained well. Those results allowed us to conclude that the prepared Co-Ni3N/NF electrocatalyst holds the promises for large-scale water electrolysis in industries. More specifically, this work provided a new perspective that the efficiency of electrocatalysts for large-scale water electrolysis can be enhanced by constructing a heterostructure with good wettability and gas repellency.

Oxygen Vacancies and Interface Engineering on Amorphous/Crystalline CrOx -Ni3 N Heterostructures toward High-Durability and Kinetically Accelerated Water Splitting.

Manipulating catalytic active sites and reaction kinetics in alkaline media is crucial for rationally designing mighty water-splitting electrocatalysts with high efficiency. Herein, the coupling between oxygen vacancies and interface engineering is highlighted to fabricate a novel amorphous/crystalline CrOx -Ni3 N heterostructure grown on Ni foam for accelerating the alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Density functional theory (DFT) calculations reveal that the electron transfer from amorphous CrOx to Ni3 N at the interfaces, and the optimized Gibbs free energies of H2 O dissociation (ΔGH-OH ) and H adsorption (ΔGH ) in the amorphous/crystalline CrOx -Ni3 N heterostructure are conducive to the superior and stable HER activity. Experimental data confirm that numerous oxygen vacancies and amorphous/crystalline interfaces in the CrOx -Ni3 N catalysts are favorable for abundant accessible active sites and enhanced intrinsic activity, resulting in excellent catalytic performances for HER and OER. Additionally, the in situ reconstruction of CrOx -Ni3 N into highly active Ni3 N/Ni(OH)2 is responsible for the optimized OER performance in a long-term stability test. Eventually, an alkaline electrolyzer using CrOx -Ni3 N as both cathode and anode has a low cell voltage of 1.53 V at 10 mA cm-2 , together with extraordinary durability for 500 h, revealing its potential in industrial applications.

Rational Design of a Ni3N0.85 Electrocatalyst to Accelerate Polysulfide Conversion in Lithium-Sulfur Batteries.

Slow kinetics of polysulfide conversion reactions lead to severe issues for lithium-sulfur (Li-S) batteries, for example, low rate capability, polysulfide migration, and low Coulombic efficiencies. These challenges hinder the practical applications of Li-S batteries. In this study, we proposed a rational strategy of tuning the d-band of catalysts to accelerate the conversion of polysulfides. Nitrogen vacancies were engineered in hexagonal Ni3N (space group P6322) to tune its d-band center, leading to the strong interaction between polysulfides and Ni3N. Because of the greater electron population in the lowest occupied molecular orbital of Li2S4, the terminal S-S bonds were weakened for breaking. Temperature-dependent experiments confirm that Ni3N0.85 demonstrates a much low activation energy, thereby accelerating the conversion of polysulfides. A Li-S cell using Ni3N0.85 can deliver a high initial discharge capacity of 1445.9 mAh g-1 (at 0.02 C) and low decay per cycle (0.039%). The Ni3N0.85 cell can also demonstrate an initial capacity of 1200.4 mAh g-1 for up to 100 cycles at a high loading of 5.2 mg cm-2. The high efficiency of rationally designed Ni3N0.85 demonstrates the effectiveness of the d-band tuning strategy to develop low-activation-energy catalysts and to promote the atomic understanding of polysulfide conversion in Li-S batteries.

A novel enzyme-free glucose and H2O2 sensor based on 3D graphene aerogels decorated with Ni3N nanoparticles.

In this work, a novel enzyme-free glucose and hydrogen peroxide (H2O2) sensor based on Ni3N nanoparticles on conductive 3D graphene aerogels (Ni3N/GA) has been successfully synthesized by using hydrothermal reaction, freeze-dried and then calcined under NH3 atmosphere. The obtained Ni3N/GA composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption isotherms and electrochemical methods. The results show the obtained 3D Ni3N/GA composites exhibit excellent electrochemical performance toward glucose oxidation and H2O2 reduction with larger catalytic rate constant Kcat value of 3.75 × 103 M-1 s -1 and 1.24 × 103 M-1 s -1, respectively. As a glucose sensor, the obtained electrode provides a wide detection range of 0.1-7645.3 µM, fast response time within 3 s, high sensitivity of 905.6 µA mM-1 cm-2 and low detection limit of 0.04 µM. For detection of H2O2, this prepared sensor offers a wide detection range (5 µM-75.13 mM), fast response time (within 5 s), sensitivity (101.9 µA mM-1 cm-2) and low detection limit (1.80 µM). This enzyme-free glucose and H2O2 sensor display satisfactory selectivity, reproducibility and long-term storage stability. Additionally, the sensor can also be used for glucose and H2O2 detection in human blood serum. The results demonstrate that 3D GA nanostructures provide an enviable conductive network for efficient charge transfer and avoid Ni3N nanoparticles aggregation, which is advantageous for electrocatalytic applications.

Porous Ni3N nanosheet array as a catalyst for nonenzymatic amperometric determination of glucose.

A glassy carbon electrode was modified with an array of porous Ni3N nanosheets (Ni3N NA) and studied for its use in non-enzymatic electrochemical detection of glucose. The morphology and structure of the Ni3N NA were characterized by scanning electron microscopy and X-ray diffraction. Electrochemical studies demonstrated that the Ni3N NA acts as an efficient catalyst for the electro-oxidation of glucose at pH 13, best at a working voltage of 0.55 V (vs. Ag/AgCl). Figures of merit include (a) high sensitivity (39 µA·mM-1·cm-2), (b) a low limit of detection (0.48 µM), and (c) a linear range that extends from 2 µM to 7.5 mM. The sensor was applied to the determination of glucose levels in human serum, and satisfactory results were obtained. Graphical abstract Nonenzymatic electrochemical glucose sensor based on porous Ni3N nanosheet array. The arrow indicates the successive addition of glucose standard solutions.