The Role of Nanomaterials in Energy Sources Development and Storage

Hydrogen is the most plentiful element in nature, which is an appropriate substitute fornonrenewable and environmentally destructive fossil fuels due to some advantages such asrenewability, storability, portability and also being non-pollutant [1]. The main advantage ofhydrogen is its environmentally friendly property since water is produced as the only by-product[2] and has an excellent energy density by weight. In the present time, platinum and platinumalloys are the best catalysts for hydrogen evaluation reaction (HER), but their application is oftenlimited due to some limitation in platinum preparation (for instance its high cost). So the searchfor new methods to reduce loaded platinum in HER catalysis has been a topic of current interest[3]. Also, Electrolysis of water to produce oxygen and hydrogen (i.e., H2O → H2 + 1/2O2)provides a favorable route for the large-scale storage of energy from the sun or other renewableresources. Over the past several decades, electrochemical water splitting has attracted a lot ofattention as a critical process in hydrogen production from electricity [4]. Moreover, Li-ionbatteries have been used in energy-storage applications, due to their superior charge storageproperties (including high capacity and low self-discharge rates) in comparison with otherrechargeable batteries. However, to achieve super-high energy density, advanced electrodematerials with high energy storage capacities must be developed to replace traditional LiCoO2cathode and graphite anode materials. Here, we introduce different new electrochemicalnanomaterials for electrochemical hydrogen/oxygen generation or as a hydrogen storage, and oras supercapacitor and/or several anodes for Li-battery, based on the fabrication of several newnanohybrids. One of them is modified polyoxometalates; that was decorated on polydiallyldimethylammonium chloride‒reduce graphene oxide (PDDA‒rGO) and PDDA‒CNT.Then, Pt nanoclusters were decorated at the surface of [PW11NiO39]5‒@PDDA‒CNT and at[PW11NiO39]5‒@PDDA‒rGO to fabricate new catalysts [3]. Another one is based on bimetallicsilicon nanostructures (Pt–M, M: Pd, Ru, Rh) on reduced graphene oxide (rGO) [2], Pd/Ptbimetallic nanofoam (Pd/Pt NFC) on Cu nanofoam substrate [1], Pd#LDH/rGOs modified withsome polymer layers as a hydrogen storage [4,] (Al-M/LDHs) modified reduced graphene oxide(rGO) and on RuO2-decorated exfoliated graphene oxide (RuO2-EGO) [5], nitrogen dopedgraphene oxide (rNGO) rNGO/LaNi-LDH [6] and rNGO/Au@LaNi-LDH [6], polybenzimidazoleand polybenzimidazole/MoS2 hybrids [7], . The nanocomposites and nanohybrids arecharacterized in detail using different electrochemical and spectroscopic methods. Thenanohybrids exhibited excellent electrocatalysts for electrochemical hydrogen evolution reactionwith a small Tafel slope, which is one of the best candidates among all the or lower Pt and/ornon-Pt electrocatalysts for electrochemical hydrogen evolution reaction with highly competitiveperformance relative to various hydrogen generation electrocatalytic materials such as MoS2 andWS2, and Pt. Recently, we have prepared Ni3S2/Ball-milled silicon flour as a bi-functionalelectrocatalyst for hydrogen and oxygen evolution reactions (OER) [8]. The isolated islandarchitecture of the bi-functional (HER and OER electrocatalyst) could act as the promisingelectrode materials for water splitting using electrochemical methods. Moreover, copper-bismuthoxide (CuBi2O4) nanoparticles were supported on nanoporous stainless steel by a simpleelectrochemical deposition method and then was employed as a binder-free electrode forsupercapacitor application [9].