Standardized procedures important for improving single-component ceramic fuel cell technology

Standardized procedures important for improving single-component ceramic fuel cell technolog

RGO-MoS₂ Supported NiCo₂O₄ Catalyst toward Solar Water Splitting and Dye Degradation

Formation of the NiCo₂O₄ (NCO) nanoparticle with the simultaneous reduction of GO and growth of MoS₂ by a two step hydrothermal process results in a 2D RGO-MoS₂ (R-MoS₂) cocatalyst layer with intimate interfacial contact with NCO. The phase purity, chemical coupling and morphology of the synthesized materials are established through X-ray diffraction, Raman and X-ray photoelectron spectroscopy studies. The ternary composite, RGO-MoS₂-NiCo₂O₄ (RM-NCO), shows excellent electrocatalytic performance toward solar driven water splitting with 3.08% solar to hydrogen (STH) conversion efficiency, photocurrent density of 5.36 mA cm^–2, injection efficiency of 97% at 1 V (vs Ag/AgCl) and long-term stability. The photo degradation (95%) of Rhodamine B under visible light irradiation is obtained in 90 min by the ternary composite (RM-NCO). The improved performance of the ternary composite, RM-NCO, over bare NCO and MoS₂, toward photocatalytic activity is achieved through the dual charge transfer pathway between interfacial layer of NCO and MoS₂ to RGO, which leads to generation of more photoinduced charge carriers and suppression of electron–hole recombination process

Visible-Light-Mediated Electrocatalytic Activity in Reduced Graphene Oxide-Supported Bismuth Ferrite

Reduced graphene oxide (RGO)-supported bismuth ferrite (BiFeO₃) (RGO–BFO) nanocomposite is synthesized via a two-step chemical route for photoelectrochemical (PEC) water splitting and photocatalytic dye degradation. The detailed structural analysis, chemical coupling, and morphology of BFO- and RGO-supported BFO are established through X-ray diffraction, Raman and X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy studies. The modified band structure in RGO–BFO is obtained from the UV–vis spectroscopy study and supported by density functional theory (DFT). The photocatalytic degradation of Rhodamine B dye achieved under 120 min visible-light illumination is 94% by the RGO–BFO composite with a degradation rate of 1.86 × 10^–2 min^–1, which is 3.8 times faster than the BFO nanoparticles. The chemical oxygen demand (COD) study further confirmed the mineralization of an organic dye in presence of the RGO–BFO catalyst. The RGO–BFO composite shows excellent PEC performance toward water splitting, with a photocurrent density of 10.2 mA·cm^–2, a solar-to-hydrogen conversion efficiency of 3.3%, and a hole injection efficiency of 98% at 1 V (vs Ag/AgCl). The enhanced catalytic activity of RGO–BFO is explained on the basis of the modified band structure and chemical coupling between BFO and RGO, leading to the fast charge transport through the interfacial layers, hindering the recombination of the photogenerated electron–hole pair and ensuring the availability of free charge carriers to assist the catalytic activity

Role of Reduced CeO₂(110) Surface for CO₂ Reduction to CO and Methanol

Density functional theory (DFT) calculations were performed to study the mechanism of carbon dioxide (CO₂) reduction to carbon monoxide (CO) and methanol (CH₃OH) on CeO₂(110) surface. CO₂ dissociates to CO on interacting with the oxygen vacancy on reduced ceria surface. The oxygen atom heals the vacancy site and regenerates the stoichiometric surface via a redox mechanism with intrinsic activation and reaction energies of 259.2 and 238.6 kJ/mol, respectively. Lateral interaction of oxygen vacancies were studied by the generation of two oxygen vacancies per unit of CeO₂ surface. Compared to a single isolated vacancy, the activation and reaction energies of CO₂ dissociation on a divacancy were approximately reduced to half of its value. Hydrogen atom coadsorbed on the surface was observed to assist CO₂ dissociation by forming a carboxyl intermediate, CO₂+H → COOH (Δ<i>E</i>_act = 39.0 kJ/mol, Δ<i>H</i> = −69.2 kJ/mol) which on subsequent dissociation produces CO via the redox mechanism. On hydrogenation, CO is likely to produce methanol. The energetics of CO hydrogenation to produce methanol showed exothermic steps with activation barriers comparable to the DFT calculations reported for Cu (111) and CeO_2–<i>x</i>/Cu­(111) interface. While on the stoichiometric surface, COOH dissociation COOH → CO+OH (Δ<i>E</i>_act = 55.6 kJ/mol, Δ<i>H</i> = 5.7 kJ/mol) is likely to be difficult as compared to rest of the elementary steps, whereas on the reduced surface the energetics of the same step were significantly lowered (Δ<i>E</i>_act = 47.4 kJ/mol, Δ<i>H</i> = −80.4 kJ/mol). In comparison, hydrogenation of methoxy, H₃CO+H → H₃COH, appears to be relatively difficult (Δ<i>E</i>_act = 58.7 kJ/mol) on the reduced surface