Nano high-entropy oxide cathode with enhanced stability for direct borohydride fuel cells

High-entropy materials have become high-activity electrocatalysis owing to their high-entropy effect and multiple active sites.Herein,we synthesize a series of carbon-supported nano high-entropy oxides(HEOs/C),specifically (PtFeCoNiCu)O/C,using a carbothermal shock (CTS) method for application as a cathode catalyst in direct borohydride fuel cells (DBFCs).The microstructure of the prepared catalysts was characterized by X-ray photoelectron spectroscopy,X-ray absorption fine structure,and transmission electron microscopy.The prepared (PtFeCoNiCu)O/C,with particle sizes ranging from 2 to 4 nm,demonstrates 3.94 transferred electrons towards the oxygen reduction reaction in an alkaline environment,resulting in a minimal H_(2)O_(2)yield of 2.6%.Additionally,it exhibits a Tafel slope of 61 mV dec-1,surpassing that of commercial Pt/C (82 mV dec-1).Furthermore,after 40,000 cycles of cyclic voltammetry(CV) testing,the half-wave potential of (PtFeCoNiCu)O/C shows a positive shift of 3 mV,with no notable decline in the limiting current density.When (PtFeCoNiCu)O/C is used as a cathode catalyst in DBFCs,the DBFC achieves a maximum power density of 441 mW cm^(-2)at 60°C and sustains a cell voltage of approximately 0.73 V after 52 h at 30°C.These findings confirm that HEO/C is a promising cathode catalyst for DBFCs.

Hydrogen Storage Alloy and Carbon Nanotubes Mixed Catalyst in a Direct Borohydride Fuel Cell

In this study, carbon nanotubes （CNTs） were mixed with ABs-type hydrogen storage alloy （HSA）, as catalyst for an anode in a direct borohydride fuel cell （DBFC）. As comparision, a series of traditional carbon materials, such as acetylene black, Vulcan XC-72R, and super activated carbon （SAC） were also employed. Electrochemical measurements showed that the electrocatalytic activity of HSA was improved greatly by CNTs. The current density of the DI3FC employing the HSA/CNTs catalytic anode could reach 1550 mA.cm-2 （at -0.6 V vs the EIg/HgO electrode） and the maximum power density of 65 mW.cm-2 for this cell could be achieved at room temperature. Furthermore, the life time test lasting for 60 h showed that the cell displayed a good stability.

Rare earth metal oxides as BH_4^--tolerance cathode electrocatalysts for direct borohydride fuel cells

Rare earth metal oxides（REMO） as cathode electrocatalysts in direct borohydride fuel cell（DBFC） were investigated.The REMO electrocatalysts tested showed favorable activity to the oxygen electro-reduction reaction and strong tolerance to the attack of BH 4-in alkaline electrolytes.The simple membraneless DBFCs using REMO as cathode electrocatalyst and using hydrogen storage alloy as anodic electrocatalyst exhibited an open circuit of about 1 V and peak power of above 60 mW/cm 2.The DBFC using Sm 2 O 3 as cathode electrocatalyst showed a relatively better performance.The maximal power density of 76.2 mW/cm 2 was obtained at the cell voltage of 0.52 V.