Recent Advances on Bimetallic Transition Metal Phosphides for Enhanced Hydrogen Evolution Reaction

Developing excellent electrocatalysts to replace noble metal catalysts and improve hydrogen production via water splitting is a daunting task. Bimetallic transition metal phosphides (TMPs) display improved performance than monometallic transition metal phosphides due to their synergistic effects. Moreover, research has proven that supporting them on conductive substrates can further enhance their electrochemical performance. Recently, metal-organic frameworks (MOFs) are incorporated into bimetallic TMPs for enhanced performance. This review starts with a synopsis of the reaction mechanisms and performance parameters of hydrogen evolution reaction (HER) electrocatalysts. Moreover, the strategies for enhancing the performance of bimetallic TMPs and improving the hydrophilicity of TMPs are also discussed. In conclusion, the challenges and perspectives of bimetallic transition metal phosphides are discussed. This review analyses the extensive progress in this research domain and proffers insights that can aptly guide the future development of more excellent TMPs and other transition metal electrocatalysts for enhanced hydrogen evolution reaction

Nickel-cobalt phosphide terephthalic acid nano-heterojunction as excellent bifunctional electrocatalyst for overall water splitting

Recent research has focused on preparing excellent and inexpensive bifunctional transition metal electrocatalysts, which is challenging. Herein, a facile synthesis strategy for preparing self-supported nickel-cobalt phosphides using terephthalic acid (H2BDC) as metal-organic framework (MOF) precursor is reported. The incorporation of the MOF precursors modulated the electronic structures and improved the performance of the bimetallic transition metal phosphides with the as-prepared electrocatalyst requiring low overpotentials of 170 mV and 323 mV to reach 50 mAcm(-2) for HER and OER, respectively. Moreover, the electrocatalyst is employed in an alkaline water electrolyzer and requires 1.57 V to attain a current density of 10 mAcm(-2) with long-term stability, surpassing many reported MOF-derived bimetallic transition metal phosphide (TMPs) electrocatalysts. This work explores the incorporation of a rarely studied MOF precursor into self-supported bimetallic TMPs and opens the prospects of designing efficient MOF-derived electrocatalysts for overall water splitting

Hierarchical WMoC nano array with optimal crystal facet as a non-noble metal cathode for proton exchange membrane water electrolyser

Highly efficient non-noble metal hydrogen evolution reaction (HER) catalysts are of particular importance for cost-effective proton exchange membrane water electrolyser (PEMWE). Here, hierarchical WMoC nano arrays (NAs) with superhydrophilic surface and optimal crystal facet is synthesized. Mo plays a crucial role in preferred growth of active crystal facet and the formation of NA. Thanks to the optimal crystal facet and unique structure, WMoC NA exhibits an enhanced HER activity and stability under high current density. PEMWE single cell based on WMoC cathode shows an outstanding performance, which obtains a current density of 1 A cm-2 at voltage of 1.888 V with N117 at 80 degrees C, making it one of the best PEMWEs using non-noble metal cathode. The single cell also shows a stable operation under 1A cm-2 at 80 degrees C over 700 h, demonstrating WMoC cathode's great potential for application use

High performance and cost-effective supported IrOx catalyst for proton exchange membrane water electrolysis

A multistep synthesis method is introduced to fabricate high performance IrOx /W-TiO2 catalyst for noble metal reduction in PEM water electrolyzers. The performances of the IrOx/W-TiO2 catalyst for oxygen evolution reaction (OER) are measured in half-cells and single-cells and compared with unsupported IrOx and commercial IrO2. In half-cell tests, IrOx/W-TiO2 displays an improved Ir mass activity compared with the unsupported IrOx, demonstrating a positive effect of the support material. In single-cell tests, the performance of IrOx/W-TiO2 also exceeds both the unsupported and commercial IrO2. The cell voltage reaches 1.602V at 1 A cm(-2) (Nafion 212) with total noble metal loading less than 0.2 mg cm(-2), suggesting that significant Ir reductions are possible by using IrOx/W-TiO2 without sacrificing the cell performance. It also shows improved durability than other unsupported catalysts at reduced Ir loading. In-situ electrochemical test reveals that the performance is associated with the enhanced conductivity of the catalyst layer. (C) 2021 Elsevier Ltd. All rights reserved

Recent advances in heterogeneous catalysis for green biodiesel production by transesterification

Heterogeneous catalysis has provided a viable alternative to homogeneous catalysis for the production of lowcost biodiesel fuel, overcoming the constraints of homogeneous catalysis. In recent years, there have been numerous breakthroughs in the development of high-efficiency and cost-effective heterogeneous-based catalysts for catalytic transesterification of triglycerides (oil or fat) to biodiesel. Because of its simplicity and low cost, the heterogeneously catalyzed transesterification reaction has long been considered the most feasible biodiesel synthesis method. The intrinsic features of nine types of heterogeneous catalysts, including heteropolyacid, zeolite, hydrotalcite, carbon and waste materials, metal, metal oxide, enzyme, and ion exchange resins, which are commonly used in today's biodiesel research, have been studied in detail. Emphasis is placed on versatile catalysts with high-activity and low production cost as they make biodiesel production more practical, efficient and sustainable. Key parameters that influence the activity of heterogeneous catalysts as well as challenges and opportunities that could motivate future exploration are also highlighted