Structure engineering of Ni2P by Mo doping for robust electrocatalytic water and methanol oxidation reactions

A smartphone-integrated CuFe aerogel nanozyme for rapid and visual detection of ascorbic acid in real samples

The development of highly active nanozymes for advanced bioanalysis has attracted considerable attention, yet significant challenges remain. Inspired by the structural features of natural oxidases with transition metal active sites, we designed a bimetallic CuFe aerogel with significantly enhanced oxidase-like activity for the facile and visual detection of ascorbic acid (AA). The incorporation of Fe into the Cu aerogel matrix resulted in a remarkable 7.8-fold increase in oxidase-like activity compared to pure Cu aerogel, as confirmed by comprehensive experimental analyses and theoretical calculations. Leveraging the inhibitory effect of AA on the Cu6Fe aerogel-catalyzed oxidation reaction, we developed a rapid and sensitive colorimetric detection method, achieving a low detection limit of 0.1 μM. Furthermore, by integrating the Cu6Fe aerogel with portable test strips and smartphone-based colorimetric analysis, we constructed a visual sensing platform capable of accurate and reliable AA quantification. The practical applicability of this platform was successfully demonstrated through the detection of AA in real-world samples, including fruits and commercial vitamin C beverages. This work not only provides a novel strategy for designing highly active metal aerogel-based nanozymes but also opens new avenues for their application in visual sensing and point-of-care diagnostics.

Structure-Activity Relationships in Oxygen Electrocatalysis

Oxygen electrocatalysis, as the pivotal circle of many green energy technologies, sets off a worldwide research boom in full swing, while its large kinetic obstacles require remarkable catalysts to break through. Here, based on summarizing reaction mechanisms and in situ characterizations, the structure-activity relationships of oxygen electrocatalysts are emphatically overviewed, including the influence of geometric morphology and chemical structures on the electrocatalytic performances. Subsequently, experimental/theoretical research is combined with device applications to comprehensively summarize the cutting-edge oxygen electrocatalysts according to various material categories. Finally, future challenges are forecasted from the perspective of catalyst development and device applications, favoring researchers to promote the industrialization of oxygen electrocatalysis at an early date.

Coordination Effect-Promoted Durable Ni(OH)2 for Energy-Saving Hydrogen Evolution from Water/Methanol Co-Electrocatalysis

Electrocatalytic water splitting is a viable technique for generating hydrogen but is precluded from the sluggish kinetics of oxygen evolution reactions (OER). Small molecule oxidation reactions with lower working potentials, such as methanol oxidation reactions, are good alternatives to OER with faster kinetics. However, the typically employed Ni-based electrocatalysts have poor activity and stability. Herein, a novel three-dimensional (3D)-networking Mo-doped Ni(OH)₂ with ultralow Ni-Ni coordination is synthesized, which exhibits a high MOR activity of 100 mA cm^-2 at 1.39 V, delivering 28 mV dec^-1 for the Tafel slope. Meanwhile, hydrogen evolution with value-added formate co-generation is boosted with a current density of more than 500 mA cm^-2 at a cell voltage of 2.00 V for 50 h, showing excellent stability in an industrial alkaline concentration (6 M KOH). Mechanistic studies based on density functional theory and X-ray absorption spectroscopy showed that the improved performance is mainly attributed to the ultralow Ni-Ni coordination, 3D-networking structures and Mo dopants, which improve the catalytic activity, increase the active site density and strengthen the Ni(OH)₂ 3D-networking structures, respectively. This study paves a new way for designing electrocatalysts with enhanced activity and durability for industrial energy-saving hydrogen production.

Construction of Core–Shell CoMoO4@γ-FeOOH Nanosheets for Efficient Oxygen Evolution Reaction

The oxygen evolution reaction (OER) occurs at the anode in numerous electrochemical reactions and plays an important role due to the nature of proton-coupled electron transfer. However, the high voltage requirement and low stability of the OER dramatically limits the total energy converting efficiency. Recently, electrocatalysts based on multi-metal oxyhydroxides have been reported as excellent substitutes for commercial noble metal catalysts due to their outstanding OER activities. However, normal synthesis routes lead to either the encapsulation of excessively active sites or aggregation during the electrolysis. To this end, we design a novel core–shell structure integrating CoMoO₄ as support frameworks covered with two-dimensional γ-FeOOH nanosheets on the surface. By involving CoMoO₄, the electrochemically active surface area is significantly enhanced. Additionally, Co atoms immerge into the γ-FeOOH nanosheet, tuning its electronic structure and providing additional active sites. More importantly, the catalysts exhibit excellent OER catalytic performance, reducing overpotentials to merely 243.1 mV a versus 10 mA cm⁻². The current strategy contributes to advancing the frontiers of new types of OER electrocatalysts by applying a proper support as a multi-functional platform.

l-Lysine derived fabrication of Cu@Ni core–satellite nanoassemblies as efficient non-Pt catalysts for the methanol oxidation reaction

With assistance of l-lysine, Cu@Ni core–satellite nanoassemblies were fabricated, which could serve as efficient non-Pt electrocatalysts for the methanol oxidation reaction due to both the component effects and structural features.

Progress in the development of heteroatom-doped nickel phosphates for electrocatalytic water splitting

Hydrogen energy is expected to replace fossil fuels as a mainstream energy source in the future. Currently, hydrogen production via water electrolysis yields high hydrogen purity with easy operation and without producing polluting side products. Presently, platinum group metals and their oxides are the most effective catalysts for water splitting; however, their low abundance and high cost hinder large-scale hydrogen production, especially in alkaline and neutral media. Therefore, the development of high-efficiency, durable, and low-cost electrocatalysts is crucial to improving the overpotential and lowering the electrical energy consumption. As a solution, Ni₂P has attracted particular attention, owing to its desirable electrical conductivity, high corrosion resistance, and remarkable catalytic activity for overall water splitting, and thus, is a promising substitute for platinum-group catalysts. However, the catalytic performance and durability of raw Ni₂P are still inferior to those of noble metal-based catalysts. Heteroatom doping is a universal strategy for enhancing the performance of Ni₂P for water electrolysis over a wide pH range, because the electronic structure and crystal structure of the catalyst can be modulated, and the adsorption energy of the reaction intermediates can be adjusted via doping, thus optimizing the reaction performance. In this review, first, the reaction mechanisms of water electrolysis, including the cathodic hydrogen evolution reaction and anodic oxygen evolution reaction, are briefly introduced. Then, progress into heteroatom-doped nickel phosphide research in recent years is assessed, and a discussion of each representative work is given. Finally, the opportunities and challenges for developing advanced Ni₂P based electrocatalysts are proposed and discussed.