The magnetism of Fe(1-x)CoxB alloys: First principle calculations
PHYSICA B-CONDENSED MATTER
Authors: Lee, P. H.; Xiao, Z. R.; Chen, K. L.; Chen, Y.; Kao, S. W.; Chin, T. S.
Calculations of magnetism are made on transition metal monoboride of Fe(1-x)CoxB, with the scale 0 <= x <= 1. In this paper, we calculate the ferromagnetic variation of transition metal monoboride by the method of virtual crystal approximation (VCA), based on density-functional theory (DFT) with generalized gradient approximation (GGA). The variations of ferromagnetism of Fe(1-x)CoxB alloys by the first-principle spin-polarized calculations are in agreement with experimental results, the prediction of the Stoner model and the Korringa-Kohn-Rostoker (KKR) method with coherent potential approximation (CPA). The spontaneous magnetization decreases with increasing x and vanishes at around x = 0.85. This complies with earlier findings. The instability at around x = 0.8 is elucidated by electron filling of the Fe 3d orbital both from valence and interstitial electrons. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
Multifunctional Co-B-O@CoxB catalysts for efficient hydrogen generation
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Authors: Guo, Yanhui; Zhang, Ruiqi; Hao, Weiju; Zhang, Jiankan; Yang, Yanjing
The development of efficient and non-noble catalyst is of great significance to hydrogen generation techniques. Three surface-oxidized cobalt borides of Co-B-O@CoxB (x = 0.5, 1 and 2) have been synthesized that can functionalize as active catalysts in both alkaline water electrolysis and the hydrolysis of sodium borohydride (NaBH4) solution. It is discovered that oxidation layer and low boron content favor the oxygen evolution reaction (OER) activity of Co-B-O@CoxB in alkaline water electrolysis. And surface-oxidized cobalt boride with low boron content is more active toward hydrolysis of NaBH4 solution. An alkaline electrolyzer fabricated using the optimized electrodes of Co-B-O@CoB2/Ni as cathode and Co-B-O@Co2B/Ni as anode can deliver current density of 10 mA cm(-2) at 1.54 V for overall water splitting with satisfactory stability. Meanwhile, Co-B-O@Co2B affords the highest hydrogen generation rate of 3.85 L min(-1) g(-1) for hydrolysis of NaBH4 at 25 degrees C. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.