Concerning efficient water splitting, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) play pivotal roles in enabling large-scale clean hydrogen production and sustainable energy solutions. However, the OER is limited by kinetic challenges due to the complexity of multistep proton-coupled electron transfer processes. Non-noble metal-based catalysts particularly layered double hydroxides (LDHs) have shown high catalytic efficiency owing to their large surface area, tunable chemical composition, and diverse nanostructures. NiCr-LDH, a layered double hydroxide composed of Ni2+ and Cr3+ ions, exhibits a unique structure that enhances its electrochemical properties for water splitting. In this study, we synthesized M-NiCr-LDH (M: Ru, Mn, Co, Fe) using a two-step hydrothermal process with varying transition metal concentrations and evaluated their electrochemical performance in an alkaline electrolyte. Incorporating the dry cathode anion exchange membrane water electrolyzer (AEMWE) system considerably improved hydrogen production, achieving a current density of 462.5mA cm-2 at 2.0 V, with scalability demonstrated through electrode expansion. Theoretical studies revealed that Fe, Ru-NiCr-LDH outperformed undoped NiCr-LDH by optimizing the electronic structure and reducing activation energies for critical steps. Specifically, Ru doping facilitated H* adsorption with the most favorable Gibbs free energy, while Fe doping enhanced the *O -> *OOH step. Hence, this approach, which leverages the incorporation of transition metal ions, is a highly effective strategy for strengthening electrocatalytic water oxidation and reduction processes in alkaline media by increasing active site availability, thus offering considerable potential for broader applications in other catalytic systems using various hydroxide-based materials.

Over the last decades, the transition metal dichalcogenide (TMD) materials have been intensively investigated for hydrogen evolution reaction (HER). Among many TMD catalysts, MoS2 and WS2 are the most efficient materials for HER application because of their advantages including earth abundance, facile synthesis, and high catalytic activities. Herein, a simple and scalable process is introduced which was employed to prepare the nanoflower (NF) heterostructure of MoS2 and WS2 (MoS2/WS2 NF). The superior catalytic activity of the synthesized MoS2/WS2 NF could be contributed by the unique properties of the heterostructure between WS2 and MoS2 materials. Low overpotential (251 mV) at a current density of 10 mA cm−2, small Tafel slope (61 mV dec−1), good conductivity, and superstability are the main properties of the prepared MoS2/WS2 NF. This work presents a new facile novel to prepare efficient catalysts which could be great candidates for HER and electrocatalytic application.

Recently, hydrogen has emerged as a prominent energy source that can be used in various technologies. Molybdenum disulfide (MoS2) 2 ) is a typical catalyst material with two-dimensional groups that exhibit Pt-like hydrogen evolution reaction (HER) performance. In addition, metal-organic frameworks (MOFs) are a group of materials with ultrahigh porosity and enormous internal surface area, which are also highly beneficial for electrochemical processes. Therefore, catalysts based on MoS2 2 and MOF materials have been extensively investigated for the production of hydrogen gases. Numerous studies have indicated that a combination of MoS2 2 and MOF materials can dramatically boost the catalytic activity of these heterostructures. In this paper, the unique properties of MoS2 2 and MOF materials and the progress and strategies to improve the HER efficiency of catalysts based on MoS2/MOF 2 /MOF hybrid materials are discussed. Furthermore, the challenges and future perspectives of these catalysts for HER are presented.

Recently, hydrogen has emerged as a prominent energy source that can be used in various technologies. Molybdenum disulfide (MoS2) is a typical catalyst material with two-dimensional groups that exhibit Pt-like hydrogen evolution reaction (HER) performance. In addition, metal-organic frameworks (MOFs) are a group of materials with ultrahigh porosity and enormous internal surface area, which are also highly beneficial for electrochemical processes. Therefore, catalysts based on MoS2 and MOF materials have been extensively investigated for the production of hydrogen gases. Numerous studies have indicated that a combination of MoS2 and MOF materials can dramatically boost the catalytic activity of these heterostructures. In this paper, the unique properties of MoS2 and MOF materials and the progress and strategies to improve the HER efficiency of catalysts based on MoS2/MOF hybrid materials are discussed. Furthermore, the challenges and future perspectives of these catalysts for HER are presented.

Developing cost-effective and stable materials for the electrocatalysis of hydrogen evolution reaction (HER) remains challenging. In this study, efficient catalysts for HER were synthesized by integrating the cobalt and molybdenum oxides via electrodeposition, followed by subsequent sulfurization of the as-prepared oxides using chemical vapor deposition (CVD). This methodology allowed the incorporation of both cobalt and molybdenum components into the catalyst in a single step. The as-synthesized CoSx@MoSx/MoOx-based catalysts exhibited excellent hydrogen production performance in acidic media owing to the presence of Co-S and Mo-S bonds in the hybrid structure. Particularly, CoSx@MoSx/MoOx(90@360) and MoSx@CoOx(180@180) displayed the best HER performances with low overpotentials of 80 mV and 150 mV, respectively. The catalysts were highly stable, with their stability preserved for over 1000 cycles with marginal reduction in overall efficiency. Therefore, these findings suggest the potential of CoSx@MoSx/MoOx and MoSx@CoOx composites as ideal candidates for developing low-cost catalysts for electrochemical hydrogen production.

Electrocatalytic carbon dioxide (CO2) reduction has emerged as a promising approach for converting CO2 into value-added products and mitigating greenhouse gas emissions. Layered double hydroxides (LDHs) and metal-organic frameworks (MOFs) have attracted significant attention as potential electrocatalysts for CO2 reduction due to their unique structural properties and tunable chemical compositions. In this review, we provide a comprehensive overview of recent advances in the utilization of LDHs and MOFs as electrocatalysts for CO2 reduction. Scrutiny on various catalysts, along with their general design ways for CO2 reduction is presented. This review will provide insight into the up-to-date research progress in MOF-based materials for CO2 conversion. Furthermore, we highlight opportunities in this field and propose future research directions aimed at optimizing the performance of LDHs and MOFs for CO2 reduction applications.

Unlocking photocatalytic potential: this review explores the remarkable properties of lead-free double halide perovskites, their synthesis methods, and their role in photocatalytic H 2 production and CO 2 reduction.

A facile method was developed to prepare a heterostructure of CoS2 nanoparticles and P-doped Ti3C2Tx for a high-performance electrocatalytic hydrogen evolution reaction. However, the performance of Ti3C2Tx is poor owing to its high overpotential. Small CoS2 nanoparticles grew well on the surface of the P-doped Ti3C2Tx, which further increased the active surface area for the adsorption of hydrogen ions. This hybrid structure exhibited high electrocatalytic activity with low overpotentials of 130 and 180 mV vs. RHE in acidic and alkaline electrolyte solutions, respectively, and excellent structural stability. The synergistic effect of the CoS2 nanoparticles and phosphorus doped Ti3C2Tx considerably enhanced the hydrogen evolution process (HER). The findings of this study suggest that the Ti3C2Tx nanosheets have excellent prospects for developing highly active electrocatalysts for water splitting.

Metal-organic frameworks (MOFs) constitute a class of crystalline porous materials employed in storage and energy conversion applications. MOFs possess characteristics that render them ideal in the preparation of electrocatalysts, and exhibit excellent performance for the hydrogen evolution reaction (HER). Herein, H–Ni/NiO/C catalysts were synthesized from a Ni-based MOF hollow structure via a two-step process involving carbonization and oxidation. Interestingly, the performance of the H–Ni/NiO/C catalyst was superior to those of H–Ni/C, H–NiO/C, and NH–Ni/NiO/C catalysts for the HER. Notably, H–Ni/NiO/C exhibited the best electrocatalytic activity for the HER, with a low overpotential of 87 mV for 10 mA cm−2 and a Tafel slope of 91.7 mV dec−1. The high performance is ascribed to the synergistic effect of the metal/metal oxide and hollow architecture, which is favorable for breaking the H–OH bond, forming hydrogen atoms, and enabling charge transport. These results indicate that the employed approach is promising for fabricating cost-effective catalysts for hydrogen production in alkaline media.

Abstract Recently, hydrogen energy has been significantly investigated by numerous technologies. To date, noble platinum group metals have often been employed to fabricate working electrodes for hydrogen evolution reaction (HER). Therefore, the demand of highly active HER catalysts based on effective and lower‐cost materials is becoming more and more critical. Transition metal dichalcogenide (TMD) materials could be one of the most suitable materials for these requirements because they possess numerous unique mechanical, electronic, and chemical characteristics that are greatly beneficial for HER processes. Among many TMD materials, tungsten disulfide (WS2) and molybdenum disulfide (MoS2) are the most well‐known TMD materials which have been intensively studied for different applications, including HER, batteries, and supercapacitors. In this review, we tried to cover the HER mechanism of catalysts and their parameters. Besides that, the structures, properties, preparation, and HER performance of catalyst materials based on WS2 and MoS2 are comprehensively discussed. After that, the challenges and future trends of catalysts based on WS2 and MoS2 for HER are also considered.

Designing of low-cost hybrid electrocatalysts for hydrogen production is of significant importance. Recently, MXene-based materials are being increasingly employed in energy storage devices owing to their layered structure and high electrical conductivity. In this study, we propose a facile hydrothermal strategy for producing WS2/Ti3C2 nanosheets that function as electrocatalysts in the hydrogen evolution reaction (HER). WS2 provides a high surface area and active sites for electrocatalytic activity, whereas MXene Ti3C2 facilitates charge transfer. As a result, the synthesized WS2/Ti3C2 offers an increased surface area and exhibits enhanced electrocatalytic activity in acidic media. The WS2/Ti3C2 (10%) catalyst exhibited a low onset potential of −150 mV vs. RHE for the HER and a low Tafel slope of ∼62 mV dec−1. Moreover, WS2/Ti3C2 (10%) exhibited a double-layer capacitance of 1.2 mF/cm-2, which is three and six times greater than those of bare WS2 and Ti3C2, respectively. This catalyst also maintained a steady catalytic activity for the HER for over 1000 cycles.

It is crucial to develop a low-cost hybrid electrocatalysts for hydrogen production. Due to their layered structure and strong electrical conductivity, MXene-based materials have been lately used more and more in energy storage devices. Herein, heteroatom- (boron and sulfur-) doped MXene (B, S-Ti 3 C 2 T x ) nanosheets are developed as efficient electrocatalysts for the hydrogen evolution reaction (HER). The synthesized B, S-Ti 3 C 2 T x has a large surface area and exhibits excellent electrocatalytic activity in acidic media. The prepared B, S-2-Ti 3 C 2 T x catalyst exhibits a low overpotential of −110 mV vs. reversible hydrogen electrode for the HER and a low Tafel slope of ∼54 mV dec −1 . Furthermore, B, S-2-Ti 3 C 2 T x shows a double-layer capacitance of 1.05 mF/cm 2 and maintains a steady catalytic activity for the HER for over 1000 cycles.

Stable, efficient catalysts are crucial for electrochemical water splitting. Metal–organic frameworks (MOFs) can be used to create electrocatalysts meeting these criteria; however, the lack of high-quality electrode materials for the hydrogen evolution reaction impedes their adoption. In this study, a hollow-structured Co/Co 3 O 4 /C composite was prepared using a Co-based MOF precursor through a two-step pyrolysis-oxidation process. This composite outperformed nonhollow Co/Co 3 O 4 /C structures as well as hollow Co/C and Co 3 O 4 /C composites as a catalyst for hydrogen production in alkaline media. It had a low overvoltage of 169 mV at a current density of 10 mA cm -2 and a moderate Tafel slope of 60.7 mV dec- 1 . Moreover, it exhibited remarkable durability with 2000 cycles and 12 h of testing. This can be attributed to the synergistic effect of Co, Co 3 O 4, and the hollow morphological architecture, which promote the dissociation of HO‒H bonds, recombination of hydrogen intermediates, and efficient electron transfer. The results of this study are highly promising for the fabrication of cost-effective electrode materials for water splitting.

The high concentration of CO 2 in the atmosphere brings adverse effects on the global climate. Consequently, researchers are relentlessly pursuing the development of efficient CO 2 reduction technologies. Among the several strategies available currently, CO 2 conversion to useful chemicals via electrochemical or photochemical processes is an incredibly exciting pathway because the driving force can potentially be sourced from the renewable energies. Due to their tunable bandgap and excellent stability, an enormous number of metal organic frameworks (MOFs) were extensively explored as efficient catalysts for CO 2 reduction. This summary collects recent works in the growth, engineering, and comprehension of CO 2 conversion using MOF-based electrocatalysts and photocatalysts. Scrutiny on various catalysts, along with their general design ways for CO 2 reduction is presented. This review will afford insight into the up-to-date research progress in MOF-based materials for CO 2 conversion.

In this study, different morphologies of molybdenum disulfide (MoS2), including MoS2 nanoparticle (NP), MoS2 nanoflower (NF), MoS2 nanosphere (NS), MoS2 nanohollow (NH), and MoS2/MoO2 composite, are successfully synthesized via a facile-route hydrothermal process employing different solutions. The structure and chemical bonding of the different morphologies of MoS2 are investigated via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Thereafter, the synthesized materials are applied to the hydrogen evolution reaction (HER) employing a three-electrode system in a standard acidic medium (0.5 M H2SO4). The MoS2 NH exhibits higher performance: an overpotential of -230 mV at -10 mAcm(-2), a Tafel slope of 64 mVdec(-1), a high double-layer capacitance (C-dl) of 11.98 mFcm(-2) and larger BET surface area (22.59 m(2)/g), as well as super stability after stability tests, representing the best catalytic behavior among the synthesized materials. The results indicate that the electrocatalytic efficiencies of materials depend on their morphologies which is highly related to the surface area of catalysts. The results avail a novel avenue for synthesizing the various morphologies of MoS2, as well as the new morphology of MoS2 (MoS2 NH). It can be a promising material for electrocatalytic and energy-storage applications.

Recently, the increase in the CO2 content in the Earth's atmosphere causes global warming and the rapid consumption of fossil fuel resources such as coal and oil. Therefore, effort is required to create clean and sustainable energy resources to address these environmental issues. In this context, hydrogen evolution from water splitting-based photoelectrochemical technologies plays a significant role as a zero CO2 emission fuel. Here, we design and prepare carbon-doped SnO2 nanostructures by a simple single-step thermal decomposition method and coated on a MoS2/p-Si substrate for hydrogen evolution by photoelectrochemical water splitting. The C-doped SnO2/MoS2/p-Si shows enhanced activity in the hydrogen evolution reaction, with an onset potential of -0.17 V at 2.73 mA/cm(2), and high stability for over 45 hours. In addition, the doping of carbon influences the shape of the nanostructures, inducing their transformation from cubical rods to polyhedral structures. This study provides a promising method for the fabrication of heterogeneous photoelectrocatalysts for overall water splitting.

Transition metal dichalcogenides (TMDs), transition metal carbides (TMCs), and transition metal oxides (TMOs) have been widely investigated for electrocatalytic applications owing to their abundant active sites, high stability, good conductivity, and various other fascinating properties. Therefore, the synthesis of composites of TMDs, TMCs, and TMOs is a new avenue for the preparation of efficient electrocatalysts. Herein, we propose a novel low-cost and facile method to prepare TMD–TMC–TMO nano-hollow spheres (WS 2 –WC–WO 3 NH) as an efficient catalyst for the hydrogen evolution reaction (HER). The crystallinity, morphology, chemical bonding, and composition of the composite material were comprehensively investigated using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The results confirmed the successful synthesis of the WS 2 –WC–WO 3 NH spheres. Interestingly, the presence of nitrogen significantly enhanced the electrical conductivity of the hybrid material, facilitating electron transfer during the catalytic process. As a result, the WS 2 –WC–WO 3 NH hybrid exhibited better HER performance than the pure WS 2 nanoflowers, which can be attributed to the synergistic effect of the W–S, W–C, and W–O bonding in the composite. Remarkably, the Tafel slope of the WS 2 –WC–WO 3 NH spheres was 59 mV dec −1 , which is significantly lower than that of the pure WS 2 NFs (82 mV dec −1 ). The results also confirmed the unprecedented stability and superior electrocatalytic performance of the WS 2 –WC–WO 3 NH spheres toward the HER, which opens new avenues for the preparation of low-cost and highly effective materials for energy conversion and storage applications.

The development of low‐cost and stable materials presents a challenging task for the electrocatalytic hydrogen evolution reaction (HER). In this work, we developed a facile strategy to fabricate efficient catalysts by incorporating amorphous molybdenum sulfide (MoSx) and Ni‐metal‐organic framework (MOF)‐74 via a solvothermal process. Owing to the formation of NiMoS phases that decrease the hydrogen adsorption energy on the catalysts, the MoSx/Ni‐MOF‐74 based catalysts deliver excellent hydrogen generation performance in acidic media. In particular, an optimal MoSx/Ni‐MOF‐74 with an amount of 40 wt% MoSx exhibited the best HER performance with a low onset voltage of −114 mV and a small Tafel slope of 53.1 mV dec−1. In addition, the stability of the catalyst was maintained for over 2000 cycles with a slight shift in performance. These results imply that the MoSx/Ni‐MOF‐74 composite is a promising candidate for the development of non‐expensive catalysts for hydrogen production using the electrochemical method.

Photocatalytic N2 fixation has emerged as a potential alternative pathway to synthesize NH3. However, poor light absorption, restricted charge separation, the extreme stability of N2 molecules caused by the N≡N bond, and the 6e--involved reactions are considered to be bottlenecks limiting the overall photocatalytic performance. In this context, the nature of the active sites plays a crucial role, which is associated with N2 adsorption, activation, and reduction. In this review, we provide forefront research on the development of highly active sites for photon-induced N2 fixation. Thus, three essential sections, namely (i) defect-rich photocatalysts, (ii) metal and nonmetal doping photocatalysts, and (iii) emerged co-catalysts, are highlighted to create a panorama of the materials approach to solar-driven N2 fixation. Finally, a summary and future outlook are given. It is hoped that this review will provide a broad picture and inspire the exploration of novel photocatalysts for efficient NH3 production.

The large energy consumption with the increasing human population and industrialization caused adverse effects on the environment as well as air pollution, water pollution, and soil pollution. Among those, air pollutants such as sulfur dioxide (SO2), nitrogen oxides (NOx), Carbon monoxide (CO), and volatile organic compounds (VOCs) not only severely affect human health but also significantly changed the global climate which ultimately resulted in many disasters worldwide. Thus, purification of air pollution is one of the most urgent issues for human beings to deal with. Due to their tunable bandgap and excellent stability, photocatalysts have shown many advantages towards the oxidation treatments of pollutants for the purification of air. In this letter, we discuss the most recent developments in emerging photocatalysts including transition metal oxides, transition metal sulfides, quantum dots and MXenes for the purification of air pollution. In addition, the insight into the performance of these emerging photocatalysts for the photocatalytic oxidation of air pollutants are provided. (C) 2021 Elsevier B.V. All rights reserved.