Effects of Ce Doping on the Photocatalytic and Electrochemical Performance of Nickel Hydroxide Nanostructures

Interfacial Coupling of Graphene with Nickel Nanoparticles for Water Splitting and Urea Oxidation: A Spectroelectrochemical Investigation

Nickel nanoparticle and graphene interfaces of various stoichiometries were created through electrodeposition techniques. The catalytic behavior of the electrodeposited films was investigated through spectro-electrochemical methodologies. UV-vis absorbance spectra of the electrodeposited films are significantly different in the air and alkaline medium. Furthermore, UV-vis and Raman spectroscopy confirmed the coupling of Ni nanoparticles (Ni-NP) with the graphene framework, along with NiO and Ni(OH)2 . A combination of Raman and impedance spectroscopy revealed that the surface adsorption and charge transfer properties of the electrodeposited films are entirely dependent on the defects on graphene structure as well as distribution of Ni-NP on graphene. The electrodeposited films possess heterogeneous catalytic properties with a low overpotential of 50 mV (10 mA/cm-2 ) for hydrogen evolution reaction, as well as 601 mV and 391 mV (at 50 mA/cm-2 ) for the oxygen evolution reaction and urea oxidation reaction, respectively. In addition, eelectrodeposited samples show extraordinary overall water splitting performance by achieving a current density of 10 mA/cm2 at a very low applied potential of 1.38 V. This synergistic coupling of Ni and graphene renders the electrodeposited samples promising candidates as electrodes for overall water splitting in alkaline and urea-supplemented solutions.

Environmentally Benign pSOFC for Emissions-Free Energy: Assessment of Nickel Network Resistance in Anodic Ni/BCY15 Nanocatalyst

Yttrium-doped barium cerate (BCY15) was used as ceramic matrix to obtain Ni/BCY15 anode cermet for application in proton-conducting solid oxide fuel cells (pSOFC). Ni/BCY15 cermets were prepared in two different types of medium, namely deionized water (W) and anhydrous ethylene glycol (EG) using wet chemical synthesis by hydrazine. An in-depth analysis of anodic nickel catalyst was made aiming to elucidate the effect of anode tablets' preparation by high temperature treatment on the resistance of metallic Ni in Ni/BCY15-W and Ni/BCY15-EG anode catalysts. On purpose reoxidation upon high-temperature treatment (1100 °C for 1 h) in air ambience was accomplished. Detailed characterization of reoxidized Ni/BCY15-W-1100 and Ni/BCY15-EG-1100 anode catalysts by means of surface and bulk analysis was performed. XPS, HRTEM, TPR, and impedance spectroscopy measurements experimentally confirmed the presence of residual metallic Ni in the anode catalyst prepared in ethylene glycol medium. These findings were evidence of strong metal Ni network resistance to oxidation in anodic Ni/BCY15-EG. Enhanced resistance of the metal Ni phase contributed to a new microstructure of the Ni/BCY15-EG-1100 anode cermet getting more stable to changes that cause degradation during operation.