Defect-rich cobalt pyrophosphate hybrids decorated Cd0.5Zn0.5S for efficient photocatalytic hydrogen evolution: Defect and interface engineering.

Photocatalysts with highly efficient charge separation are of critical significance for improving photocatalytic hydrogen production performance. Herein, a cost-effective and high-performance composite photocatalyst, cobalt-phosphonate-derived defect-rich cobalt pyrophosphate hybrids (CoPPi-M) modified Cd0.5Zn0.5S is rationally devised via defect and interface engineering, in which the co-catalyst CoPPi-M delivers a strong interaction with host photocatalyst Cd0.5Zn0.5S, rendering Cd0.5Zn0.5S/CoPPi-M with a remarkably improved efficiency of charge separation and migration. Besides, Cd0.5Zn0.5S/CoPPi-M exhibits a hydrophilic surface with ample access to electrons and a strong reduction ability of electrons. Benefiting from these advantages, the integration of defect-rich cobalt pyrophosphate and Cd0.5Zn0.5S enables Cd0.5Zn0.5S/CoPPi-M-5% with high photocatalytic H2 production rate of 6.87 mmol g-1h-1, which is 2.46 times higher than that of pristine Cd0.5Zn0.5S, and the notable apparent quantum efficiency (AQE) is 20.7% at 420 nm. This work provides a promising route for promoting the photocatalytic performance of non-precious hybrid photocatalyst via defect and interface engineering, and advances energy-generation and environment-restoration devices.

Nanoporous Metal Phosphonate Hybrid Materials as a Novel Platform for Emerging Applications: A Critical Review.

Nanoporous metal phosphonates are propelling the rapid development of emerging energy storage, catalysis, environmental intervention, and biology, the performances of which touch many fundamental aspects of portable electronics, convenient transportation, and sustainable energy conversion systems. Recent years have witnessed tremendous research breakthroughs in these fields in terms of the fascinating pore properties, the structural periodicity, and versatile skeletons of porous metal phosphonates. This review presents recent milestones of porous metal phosphonate research, from the diversified synthesis strategies for controllable pore structures, to several important applications including adsorption and separation, energy conversion and storage, heterogeneous catalysis, membrane engineering, and biomaterials. Highlights of porous structure design for metal phosphonates are described throughout the review and the current challenges and perspectives for future research in this field are discussed at the end. The aim is to provide some guidance for the rational preparation of porous metal phosphonate materials and promote further applications to meet the urgent demands in emerging applications.

Mesoporous CdxZn1-xS with abundant surface defects for efficient photocatalytic hydrogen production.

The practical application of photocatalytic water splitting for hydrogen evolution hinges on the development of high-efficient and low-cost photocatalysts. Defects engineering has emerged as a promising strategy to enhance photocatalytic activity effectively. Herein, a facile and versatile co-precipitation method is proposed to fabricate mesoporous Cd-Zn-S solid solutions (E-CdxZn1-xS) with abundant surface defects by the inorganic salts formed in the reaction system as self-template. Compared with Cd-Zn-S solid solutions (W-Cd0.65Zn0.35S) prepared by the traditional co-precipitation method, the enhanced specific surface area and abundant surface defects endow E-Cd0.65Zn0.35S with more accessible active sites and effective separation of electron-hole pairs for the photocatalytic water splitting reaction. The E-Cd0.65Zn0.35S solid solution exhibits hydrogen evolution rate of 5.2 mmol h-1 g-1 without loading noble metal as cocatalyst under visible light, which is 1.13 times higher than that of W-Cd0.65Zn0.35S sample. The present work provides a simple, low-cost and prospective strategy for the synthesis of defective Cd-Zn-S solid solutions, and it also delivers guidance to design and develop the advanced visible-light photocatalyst in the future.

Transition Metal Phosphide-Based Materials for Efficient Electrochemical Hydrogen Evolution: A Critical Review.

As hydrogen has been increasingly considered as promising sustainable energy supply, electrochemical overall water splitting driven by highly efficient non-noble metal electrocatalysts has aroused extensive attention. Transition metal phosphides (TMPs) have demonstrated remarkable electrocatalytic performance, including high activity and robust durability towards hydrogen evolution reaction (HER) in acidic and alkaline as well as neutral electrolytes. In this Review, up-to-date progress of TMP-based HER electrocatalysts is summarized. Various synthesis strategies of TMPs based on selected phosphorus sources are presented, and the reaction mechanisms of HER as well as the contribution of phosphorus in the TMPs to HER activity are briefly discussed. The multiscale approaches for promoting the activity and stability of TMP-based catalysts are discussed with respect to intrinsic electronic structure, hybrids, microstructure, and working electrode interface. Some crucial issues and future perspectives of TMPs are pointed out. These modulated approaches and challenges are also instructive for constructing other high-activity energy-related electrocatalysts.

Ambient Ammonia Electrosynthesis: Current Status, Challenges, and Perspectives.

Ammonia (NH3 ) electrosynthesis from atmospheric nitrogen (N2 ) and water is emerging as a promising alternative to the energy-intensive Haber-Bosch process; however, such a process is difficult to perform due to the inherent inertness of N2 molecules together with low solubility in aqueous solutions. Although many active electrocatalysts have been used to electrocatalyze the N2 reduction reaction (NRR), unsatisfactory NH3 yields and lower Faraday efficiency are still far from practical industrial production, and thus, considerable research efforts are being devoted to address these problems. Nevertheless, most reports still mainly focus on the preparation of electrocatalysts and largely ignore a summary of optimization-modification strategies for the NRR. In this review, a general introduction to the NRR mechanism is presented to provide a reasonable guide for the design of highly active catalysts. Then, four categories of NRR electrocatalysts, according to chemical compositions, are surveyed, as well as several strategies for promoting the catalytic activity and efficiency. Later, strategies for developing efficient N2 fixation systems are discussed. Finally, current challenges and future perspectives in the context of the NRR are highlighted. This review sheds some light on the development of highly efficient catalytic systems for NH3 synthesis and stimulates research interests in the unexplored, but promising, research field of the NRR.

Iron-Salt Thermally Emitted Strategy to Prepare Graphene-like Carbon Nanosheets with Trapped Fe Species for an Efficient Electrocatalytic Oxygen Reduction Reaction in the All-pH Range.

Earth-abundant, highly active, and durable electrocatalysts toward oxygen reduction reaction (ORR) in the all-pH range are highly required for practical application of electrochemical energy conversion technologies. Here, non-noble-metal graphene-like carbon nanosheets with trapped Fe species (Fe-N/GPC) are developed by an iron-salt thermally emitted strategy, which integrates the modulation of the electronic structure for boosted intrinsic activity with the engineering of hierarchical porosity for enriched active sites. The ORR electrocatalytic performance of Fe-N/GPC-800 achieves the half-wave potentials of 0.86 and 0.77 V with limiting current densities of 6.1 and 4.7 mA cm-2 in 0.1 M KOH and 0.1 M PBS solutions, respectively, as well as respectable stability. Furthermore, Fe-N/GPC-800 also shows considerable ORR catalytic activity in acid media accompanied by stability superior to those of Pt/C catalysts. The as-prepared Fe-N/GPC-800, as a cathodic catalyst, is assessed in a Zn-air battery test and delivers an open-circuit voltage of 1.44 V with a power density of 134 mW cm-2 as well as the outstanding durability after 350 cycles at 10 mA cm-2, demonstrating appreciable promise in application of metal-air batteries. This work provides an enabling and versatile strategy for facile and scale-up preparation of high-performance non-noble-metal electrocatalysts.

Well-Defined Mo2C Nanoparticles Embedded in Porous N-Doped Carbon Matrix for Highly Efficient Electrocatalytic Hydrogen Evolution.

On the design of efficient and affordable electrocatalysts for water reduction half reaction, this paper fabricates molybdenum carbide nanoparticles uniformly loaded in highly porous N-doped carbon matrix derived from polyaniline-molybdate monolith with the use of graphitic carbon nitride (g-C3N4) as template. The obtained molybdenum carbide-carbon hybrid catalysts (MoC@NCS) exhibit extraordinarily electrochemical hydrogen evolution activity with a small overpotential of 89 and 81 mV to deliver a current density of 10 mA cm-2 in alkaline (1.0 M KOH) and acidic (0.5 M H2SO4) medium, respectively, even comparable to noble-metal Pt/C benchmark. Specially, MoC@NCS also shows excellent long-term durability in alkaline or acidic electrolyte. Furthermore, the obtained carbon matrix (NCS) featuring high content of N dopants and hierarchically porous architecture exhibits high catalytic efficiency for oxygen evolution reaction in alkaline electrolyte. For a further step, the obtained NCS coupled with the MoC@NCS, working as anodic and cathodic electrodes, in a two-electrode alkaline electrolyzer for overall water splitting, which can obtain a current density of 10 mA cm-2 at 1.69 V, along with robust operation durability. The synergistic effect of the porous carbon matrix of high nitrogen content and the molybdenum carbide nanoparticles of uniform distribution, together with hierarchically porous structure, should be responsible for the outstanding electrocatalytic HER performance. This work presents an easy and cost-effective strategy to prepare molybdenum-based materials with controlled size for electrocatalytic hydrogen evolution.

Uniquely integrated Fe-doped Ni(OH)2 nanosheets for highly efficient oxygen and hydrogen evolution reactions.

Developing high-efficiency electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital for the production of hydrogen on a large scale by electrocatalytic splitting of water. Herein, Fe-doped Ni(OH)2 nanosheets directly grown on commercial Ni foam (FeNiOH/NF) were fabricated through a facile hydrothermal method in (NH4)2S2O8 aqueous solution containing iron salts. The integrated architecture with hierarchical pores is beneficial for exposing sufficient catalytically active sites and providing evaluated structural and electrical properties. In particular, the Fe-induced partial-charge-transfer greatly modifies the electronic structure of Ni(OH)2, which evidently promotes the electrocatalytic activity of the as-fabricated FeNiOH/NF for OER and HER. Thus, as an electrocatalyst for OER, FeNiOH/NF exhibits excellent activity with overpotentials of 271 and 318 mV to deliver current densities of 20 and 100 mA cm-2, respectively, with a small Tafel slope of 72 mV dec-1 in 1.0 M KOH, demonstrating the very high level of novelty and sufficient improvement over the current state-of-the-art IrO2 electrocatalyst. Most importantly, there is an increase in overpotential by only 23 mV during continuous reaction for over 20 h at an applied potential of 1.62 V to deliver current density of 500 mA cm-2. The as-fabricated electrocatalyst also enables high HER activity with robust stability. Finally, an overall water splitting current density of 10 mA cm-2 can be obtained at a cell voltage of 1.67 V in a two-electrode alkaline electrolyzer using FeNiOH/NF as both anode and cathode, along with impressive operation stability. This development with significant over the state-of-the-art IrO2 electrocatalyst can be widely extended to large-scale fabrication of versatile electrocatalysts for efficient water splitting technology.

Determination and quality evaluation of green tea extracts through qualitative and quantitative analysis of multi-components by single marker (QAMS).

The quality of tea is mainly attributed to tea polyphenols and caffeine. In this paper, a new strategy for quality evaluation of green tea extracts was explored and verified through qualitative and quantitative analysis of multi-components by single marker (QAMS). Taguchi Design was introduced to evaluate the fluctuations of the relative conversion factors (fx) of tea catechins, gallic acid and caffeine to epigallocatechin gallate. The regression model (Sig.=0.000) and the deviations (R(2)>0.999) between QAMS and normal external standard method proved the consistency of the two methods. Hierarchical cluster analysis and canonical discriminant analysis were employed to classify 26 batches of commercial Longjing green tea extracts (LJGTEs) collected from different producers. The results showed a significant difference in component profile between the samples from different origins. The QAMS method was verified to be an alternative and promising method to comprehensively and effectively control the quality of LJGTEs from different origins.