Altering the surface stoichiometry of semiconductor electrodes is known to affect the photoelectrochemical (PEC) response. To date, several reports have hinted at the influence of the surface Bi:V ratio on the solar water oxidation performance of BiVO4 photoanodes, but only a handful of strategies have been reported to afford to fine-tune such surface stoichiometry while a comprehensive understanding of an atomic level of the role of the surface termination remains elusive. Herein, we report a new methodology that modulates the surface Bi:V ratio and, in turn, maximizes the PEC performance towards the oxygen evolution reaction (OER). We found that annealing in the presence of ammonium metavanadate drastically reduces the surface recombination while improving the charge separation. Detailed characterization revealed that this treatment filled the native surface vanadium vacancies, which are found to act as recombination centers, while inducing a significant increase in the density of oxygen vacancies, which reinforced the built-in electric field that drives the charge separation. Interestingly, coating with NiFeOx improves, especially, the charge separation in surface V-rich BiVO4. Results suggest that the V-rich surface termination altered the surface energetics of BiVO4 leading to an improved band alignment across the interface. Overall, these results provide a new platform to modulate the surface stoichiometry of BiVO4 thin films while shedding new light on the mechanisms whereby the surface termination governs the PEC response.

A computational methodology for screening aluminum-based spinel oxides for photoelectrochemical water splitting has been developed by combining HSE06 and PBE+U calculations. The method, which can be extended to other ternary oxides, provides values for formation energies, band gaps, band edge positions, and carrier effective masses. The formation energies indicate that the Al spinels of Mg, Co, Ni, and Zn (successfully synthesized using a sol-gel method) are among the most stable in the series. Except for the Mg and Zn cases, the electronic structures of the spinels are rather similar, with band gaps separating occupied and empty 3d metal states. The charge-transfer band gap values are found to be above 3 eV, limiting the use of these materials in solar water splitting, although an estimate of the band edge positions indicates that, in general, both conduction band electrons and valence band holes can promote water reduction and oxidation, respectively. The effective masses of the charge carriers suggest that the spinels are n-type semiconductors as experimentally demonstrated. Importantly, both the UV-vis spectra and the photoelectrochemical results qualitatively agree with the theoretical electronic structure. In general vein, this work demonstrates the potential of theoretical screening for the development and selection of new photoelectrode materials based on ternary oxides for their application in solar water splitting.

Esta investigacion se ha llevado a cabo con el apoyo del Programa de Redes-I3CE de investigacion en docencia universitaria del Instituto de Ciencias de la Educacion de la Universidad de Alicante (convocatoria 2020-21) (Ref.:5252).

Homemade non-critical raw materials such as Ni or NiCu co-catalysts were added at the photocathode of a tandem cell, constituted by photoelectrodes made of earth-abundant materials, to generate green solar hydrogen from photoelectrochemical water splitting. Oxygen evolving at the Ti-and-P-doped hematite/TCO-based photoanode and hydrogen at the cupric oxide/GDL-based photocathode are separated by an anion exchange polymer electrolyte membrane placed between them. The effect of the aforementioned co-catalysts was studied in a complete PEC cell in the presence of the ionomer dispersion and the anionic membrane to evaluate their impact under practical conditions. Notably, different amounts of Ni or NiCu co-catalysts were used to improve the hydrogen evolution reaction (HER) kinetics and the overall solar-to-hydrogen (STH) efficiency of the photoelectrochemical cells. At −0.6 V, in the bias-assisted region, the photocurrent density reaches about 2 mA cm−2 for a cell with 12 µg cm−2 of Ni loading, followed by 1.75 mA cm−2 for the cell configuration based on 8 µg cm−2 of NiCu. For the best-performing cell, enthalpy efficiency at −0.4 V reaches a first maximum value of 2.03%. In contrast, the throughput efficiency, which is a ratio between the power output and the total power input (solar + electric) provided by an external source, calculated at −1.225 V, reaches a maximum of 10.75%. This value is approximately three times higher than the best results obtained in our previous studies without the use of co-catalysts at the photocathode.

Tandem photoelectrochemical cells (PECs), made up of a solid electrolyte membrane between two low-cost photoelectrodes, were investigated to produce "green" hydrogen by exploiting renewable solar energy. The assembly of the PEC consisted of an anionic solid polymer electrolyte membrane (gas separator) clamped between an n-type Fe(2)O(3)photoanode and a p-type CuO photocathode. The semiconductors were deposited on fluorine-doped tin oxide (FTO) transparent substrates and the cell was investigated with the hematite surface directly exposed to a solar simulator. Ionomer dispersions obtained from the dissolution of commercial polymers in the appropriate solvents were employed as an ionic interface with the photoelectrodes. Thus, the overall photoelectrochemical water splitting occurred in two membrane-separated compartments, i.e., the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. A cost-effective NiFeOx co-catalyst was deposited on the hematite photoanode surface and investigated as a surface catalytic enhancer in order to improve the OER kinetics, this reaction being the rate-determining step of the entire process. The co-catalyst was compared with other well-known OER electrocatalysts such as La0.6Sr0.4Fe0.8CoO3(LSFCO) perovskite and IrRuOx. The Ni-Fe oxide was the most promising co-catalyst for the oxygen evolution in the anionic environment in terms of an enhanced PEC photocurrent and efficiency. The materials were physico-chemically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

Numerosos organismos internacionales han alertado de la existencia de una brecha de genero en la formacion universitaria cientifico-tecnica. En este contexto, se ha investigado de manera cuantitativa la posible existencia de patrones de genero en los resultados academicos del area de Quimica Fisica en los Grados en Quimica e Ingenieria Quimica de la Universidad de Alicante. Para ello, se han utilizado los resultados del alumnado en varios elementos de evaluacion para dos asignaturas del area de la Quimica Fisica (Quimica Fisica Aplicada y Quimica Fisica Avanzada), con el fin de analizarlos estadisticamente, tratando de identificar diferencias significativas en funcion del genero. El tratamiento de los datos muestra que existen pequenas diferencias en los resultados de las practicas de laboratorio. Sin embargo, no hay diferencias significativas en las calificaciones finales de ambos generos.

El trabajo de la red tiene como objetivo relacionar las dificultades de aprendizaje en asignaturas de Quimica Fisica con la formacion fisicomatematica del alumnado, y con el uso y conocimiento de herramientas matematicas de software. El estudio se ha basado en una encuesta anonima realizada a alumnos del tercer curso del grado en Quimica, con preguntas sobre: i) nivel de conocimientos en Matematicas, Fisica e Informatica del alumno al inicio de sus estudios de grado, ii) conocimiento y uso de herramientas matematicas de software, iii) conocimiento y uso de programas de tratamiento, visualizacion y presentacion de datos, y iv) sobre el grado de formacion adquirido en diferentes aspectos matematicos e informaticos (incluyendo herramientas y lenguajes de programacion) durante sus estudios universitarios. El analisis de las encuestas y las correlaciones observadas ponen de manifiesto las principales carencias y debilidades en la formacion fisicomatematica de los estudiantes del grado en Quimica en la Universidad de Alicante. Teniendo en cuenta los resultados obtenidos, asi como otros planes de estudios universitarios de Quimica, se realizan propuestas para mejorar la formacion basica de los estudiantes y la adquisicion de competencias practicas en este tipo de materias.

Este estudio tiene como objetivo conocer las principales dificultades de aprendizaje en asignaturas de Quimica Fisica y su relacion con la formacion fisicomatematica del alumnado, y, mas en concreto, con el uso y conocimiento de herramientas de software matematico. A partir de los resultados, se pretende elaborar propuestas encaminadas a mejorar la formacion de los estudiantes y su adquisicion de competencias practicas. La informacion usada para la elaboracion del estudio se ha obtenido mediante una encuesta anonima realizada a alumnos del tercer curso del grado en Quimica, que incluye preguntas sobre: i) nivel de conocimientos en matematicas, fisica e informatica del alumno al inicio de sus estudios de grado, ii) conocimiento y uso de diferentes herramientas matematicas de software, iii) conocimiento y uso de programas de tratamiento, visualizacion y presentacion de datos, y iv) sobre el grado de formacion adquirido en diferentes aspectos matematicos e informaticos (incluyendo tambien herramientas y lenguajes de programacion) durante sus estudios universitarios. El analisis de las encuestas y las correlaciones observadas han puesto de manifiesto las principales carencias y debilidades en la formacion fisicomatematica de los estudiantes del grado en Quimica en la Universidad de Alicante. Teniendo en cuenta los resultados obtenidos, asi como otros planes de estudios universitarios de Quimica, se presentan propuestas para mejorar la formacion basica de los estudiantes en este tipo de materias.