Direct Synthesis of Molybdenum Phosphide Nanorods on Silicon Using Graphene at the Heterointerface for Efficient Photoelectrochemical Water Reduction

Transition metal phosphides(TMPs)and transition metal dichalcogenides(TMDs)have been widely investigated as photoelectrochemical(PEC)catalysts for hydrogen evolution reaction(HER).Using high-temperature processes to get crystallized compounds with large-area uniformity,it is still challenging to directly synthesize these catalysts on silicon photocathodes due to chemical incompatibility at the heterointerface.Here,a graphene interlayer is applied between p-Si and MoP nanorods to enable fully engineered interfaces without forming a metallic secondary compound that absorbs a parasitic light and provides an inefficient electron path for hydrogen evolution.Furthermore,the graphene facilitates the photogenerated electrons to rapidly transfer by creating Mo-O-C covalent bondings and energetically favorable band bending.With a bridging role of graphene,numerous active sites and anti-reflectance of MoP nanorods lead to significantly improved PEC-HER performance with a high photocurrent density of 21.8 mA cm−2 at 0 V versus RHE and high stability.Besides,low dependence on pH and temperature is observed with MoP nanorods incorporated photocathodes,which is desirable for practical use as a part of PEC cells.These results indicate that the direct synthesis of TMPs and TMDs enabled by graphene interlayer is a new promising way to fabricate Si-based photocathodes with high-quality interfaces and superior HER performance.

Effect of Reduction Temperature on Hydrofining Performance of Supported Molybdenum Phosphide Catalyst

A series of supported molybdenum phosphide catalysts were prepared by impregnation method. XRD, TG-DTG, XPS and BET were used to study the phase, compositions and surface areas of the prepared catalysts. A model reactant containing thiophene, pyridine and cyclohexene was used for the measurements of catalytic activities. The effect of reduction temperature on catalytic activities was investigated. The analysis results by XRD and BET are very different when the reduction temperature is changed from 400 to 900 ℃. MoP/γ-Al2O3 catalysts and CoMoP/γ-Al2O3 catalysts prepared at the reduction temperature of 500 ℃ are the most active ones.

Beyond the conventional Dirac-Weyl-Majorana classification-Observation of three-component fermions in the topological semimetal molybdenum phosphide

Subject Code:A04With the support by the National Natural Science Foundation of China,a collaborative research team led by Prof.Ding Hong(丁洪),Prof.Qian Tian(钱天),and Prof.Shi Youguo(石友国)from the Institute of Physics,Chinese Academy of Sciences(IOP,CAS)has made a major breakthrough in the study

Electrochemical Surface Restructuring of Phosphorus-Doped Carbon@MoP Electrocatalysts for Hydrogen Evolution

The hydrogen evolution reaction(HER) through electrocatalysis is promising for the production of clean hydrogen fuel. However,designing the structure of catalysts,controlling their electronic properties,and manipulating their catalytic sites are a significant challenge in this field. Here,we propose an electrochemical surface restructuring strategy to design synergistically interactive phosphorus-doped carbon@MoP electrocatalysts for the HER. A simple electrochemical cycling method is developed to tune the thickness of the carbon layers that cover on MoP core,which significantly influences HER performance. Experimental investigations and theoretical calculations indicate that the inactive surface carbon layers can be removed through electrochemical cycling,leading to a close bond between the MoP and a few layers of coated graphene. The electronsdonated by the MoP core enhance the adhesion and electronegativity of the carbon layers;the negatively charged carbon layers act as an active surface. The electrochemically induced optimization of the surface/interface electronic structures in the electrocatalysts significantly promotes the HER. Using this strategy endows the catalyst with excellent activity in terms of the HER in both acidic and alkaline environments(current density of 10 mA cm^(-2) at low overpotentials,of 68 mV in 0.5 M H_(2)SO_(4) and 67 mV in 1.0 M KOH).

Phytic acid-derived fabrication of ultra-small MoP nanoparticles for efficient CO methanation: Effects of P/Mo ratios

Molybdenum phosphide(MoP) catalyst has been widely applied in hydrogenation reactions, while the preparation of unsupported MoP catalysts with ultra-small size and large specific surface area(SBET) is still challenging. Herein, we have provided a facile method for preparing a series of MoP-x(x=P/Mo ratios ranging from 1 to 5) catalysts by pyrolyzing phytic acid(PA)-derived Mo complexes in a H2 atmosphere. The physicochemical properties and the catalytic activity of MoP catalysts were investigated. The results showed that the obtained MoP-5 catalyst had the largest SBETand exhibited ultra-small nanoparticle diameter of 3.6 nm, which ascribed to the chelation of PA and the confinement of deposited products.As the content of PA increased, the synthetic mechanism of MoP was also affected, which led to the difference in the valence of surface Mo species. The characterization results further confirmed that Moδ+ sites in MoP catalysts are active sites for methanation reaction and its content on the surface of MoP-x catalysts determines the catalytic activity.

MoP nanoparticles with a P-rich outermost atomic layer embedded in N-doped porous carbon nanofibers： Self-supported electrodes for efficient hydrogen generation

Despite being pursued for a long time, hydrogen production via water splitting is still a huge challenge mainly due to a lack of durable and efficient catalysts. Molybdenum phosphide （MOP） is theoretically capable of efficient hydrogen evolution reaction （HER） catalysis, however, there is still room for further improvement in its performance. Herein, we propose a design for MoP with a P-rich outermost atomic layer for enhancing HER via complementary theoretical and experimental validation. The correlation of computational results suggests that the P-terminated surface of MoP plays a crucial role in determining its high-efficiency catalytic properties. We fabricated a P-rich outermost atomic layer of MoP nanoparticles by using N-doped porous carbon （MoP@NPCNFs） to capture more P on the surface of MoP and limit the growth of nanoparticles. Further, the as-prepared material can be directly employed as a self-supported electrocatalyst, and it exhibits remarkable electrocatalytic activity for HER in acidic media; it also reveals excellent long-term durability for up to 5,000 cycles with negligible loss of catalytic activity.

Growth of 2D MoP single crystals on liquid metals by chemical vapor deposition

Two-dimensional(2 D) transition metal phosphides(TMPs) are predicted with many novel properties and various applications. As a member of TMPs family, molybdenum phosphide(MoP) exhibits many exotic physicochemical properties. However, the synthesis of high-quality2 D MoP single crystals is not reported due to the lack of reliable fabrication method, which limits the exploration of 2 D MoP. Here, we report the growth of high-quality ultrathin MoP single crystals with thickness down to 10 nm on liquid metals via chemical vapor deposition(CVD). The smooth surface of liquid Ga is regarded as a suitable growth substrate for producing 2 D MoP single crystals. The Mo source diffuses toward the Ga surface due to the high surface energy to react with phosphorus source, thus to fabricate ultrathin MoP single crystals. Then, we study the second harmonic generation(SHG) of 2 D MoP for the first time due to its intrinsic noncentrosymmetric structure. Our study provides an new approach to synthesize and explore other 2 D TMPs for future applications.