The Catalytic Role of D-block Elements and Their Compounds for Improving Sorption Kinetics of Hydride Materials: A Review

Pratibha Pal,Ankur Jain,Jyh-Ming Ting,Shivani Agarwal,Takayuki Ichikawa

doi:10.3390/reactions2030022

Abstract

The goal of finding efficient and safe hydrogen storage material motivated researchers to develop several materials to fulfil the demand of the U.S. Department of Energy (DOE). In the past few years, several metal hydrides, complex hydrides such as borohydrides and alanates, have been researched and found efficient due to their high gravimetric and volumetric density. However, the development of these materials is still limited by their high thermodynamic stability and sluggish kinetics. One of the methods to improve the kinetics is to use catalysts. Among the known catalysts for this purpose, transition metals and their compounds are known as the leading contender. The present article reviews the d-block transition metals including Ni, Co, V, Ti, Fe and Nb as catalysts to boost up the kinetics of several hydride systems. Various binary and ternary metal oxides, halides and their combinations, porous structured hybrid designs and metal-based Mxenes have been discussed as catalysts to enhance the de/rehydrogenation kinetics and cycling performance of hydrogen storage systems.

Highlights

The search for clean and abundant energy sources to compete with fossil fuels brings us to hydrogen as a next-generation energy carrier
In summary, it can be understood that easy synthesized nanoparticles, hybrid structure, selection of suitable metal, core-shell designs, metal catalysts supported on a matrix which can provide high surface area and addition of graphene and carbon to prohibit the agglomeration of material are the key factors in designing the suitable catalysts for hydrogen storage application
The use of a suitable catalyst can improve the kinetics of hydride materials

Summary

Introduction

The search for clean and abundant energy sources to compete with fossil fuels brings us to hydrogen as a next-generation energy carrier. The safety risks due to high pressure cannot be avoided Both techniques, i.e., compressed hydrogen gas and low-temperature liquefied hydrogen gas, have their own disadvantages and are unrealistic for commercial use. Researchers have been attracted by solid-state hydrogen storage in materials due to its high gravimetric and volumetric capacities, ease of handling and safety. Regardless of the high gravimetric capacity, these materials possess serious thermodynamic and kinetic issues that create problems such as high stability (requiring high operating temperature) and slow reaction rate (causing slow charging/discharging). Nanosizing greatly influences the size of particles (generally by using the high-energy ball milling technique) and nanoconfinement is where the nanoparticles are supported on the porous catalyst These techniques improve the thermodynamics and reversibility of the system but are helpful to enhance the rate of reaction. To understand the problems related to kinetics in detail, we will move towards the section of this article

Basic Understanding of Kinetics and a Light on the Kinetics of Metal Hydride

Transition Unary Metals as Catalyst

D-block Ternary Metal Catalysts and Miscellaneous Catalysts

Findings

Summary and Future Perspective