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1. Water Splitting Electrocatalysis within Layered Inorganic Nanomaterials

   https://doi.org/10.5772/intechopen.88116  

   Ramos-Garcés, Mario V; Sanchez, Joel; Barraza_Alvarez, Isabel; Wu, Yanyu; Villagrán, Dino; Jaramillo, Thomas F; Colón, Jorge L (February 2020, IntechOpen)

   Eyvaz, M; Yüksel, E (Ed.)

   The conversion of solar energy into chemical fuel is one of the “Holy Grails” of 21st century chemistry. Solar energy can be used to split water into oxygen and protons, which are then used to make hydrogen fuel. Nature is able to catalyze both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) required for the conversion of solar energy into chemical fuel through the employment of enzymes that are composed of inexpensive transition metals Instead of using expensive catalysts such as platinum, cheaper alternatives (such as cobalt, iron, or nickel) would provide the opportunity to make solar energy competitive with fossil fuels. However, obtaining efficient catalysts based on earth abundant materials is still a daunting task. Progress in finding an ideal catalyst for the OER has been challenging as it appears that the overpotential for these catalysts have plateaued. Recent theory has shown that nanoscopic confinement of catalysts into 3D frameworks increases stability and efficiency of catalysts for OER. We are studying the use of the layered inorganic nanomaterial zirconium phosphate (ZrP) for water splitting. In this chapter we review the advancements made with ZrP as a support for transition metals for the OER. Our studies have found that ZrP is a suitable support for transition metals as it provides an accessible surface where the OER can occur. Further findings have also show that exfoliation of ZrP increases the availability of sites where active species can be adsorbed and performance is improved with this strategy. 

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2. An immobilized (carbene)nickel catalyst for water oxidation

   https://doi.org/10.1016/j.poly.2024.116880  

   Lu, Zhiyao; Mitra, Debanjan; Narayan, Sri R.; Williams, Travis J. (February 2024, Polyhedron)

   Gerard Parking (Ed.)

   The oxygen evolution reaction (OER) of water splitting is essential to electrochemical energy storage applications. While nickel electrodes are widely available heterogeneous OER catalysts, homogeneous nickel catalysts for OER are underexplored. Here we report two carbene-ligated nickel(II) complexes that are exceptionally robust and efficient homogeneous water oxidation catalysts. Remarkably, these novel nickel complexes can assemble a stable thin film onto a metal electrode through poly-imidazole bridges, making them supported heterogeneous electrochemical catalysts that are resilient to leaching and stripping. Unlike molecular catalysts and nanoparticle catalysts, such electrode-supported metal-complex catalysts for OER are rare and have the potential to inspire new designs. The electrochemical OER with our nickel-carbene catalysts exhibits excellent current densities with high efficiency, low Tafel slope, and useful longevity for a base metal catalyst. Our data show that imidazole carbene ligands stay bonded to the nickel(II) centers throughout the catalysis, which allows the facile oxygen evolution. 

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3. Preparation of Zirconium Phosphate Nanomaterials and Their Applications as Inorganic Supports for the Oxygen Evolution Reaction

   https://doi.org/10.3390/nano10050822  

   Ramos-Garcés, Mario V.; Colón, Jorge L. (May 2020, Nanomaterials)

   Zirconium phosphate (ZrP) nanomaterials have been studied extensively ever since the preparation of the first crystalline form was reported in 1964. ZrP and its derivatives, because of their versatility, have found applications in several fields. Herein, we provide an overview of some advancements made in the preparation of ZrP nanomaterials, including exfoliation and morphology control of the nanoparticles. We also provide an overview of the advancements made with ZrP as an inorganic support for the electrocatalysis of the oxygen evolution reaction (OER). Emphasis is made on how the preparation of the ZrP electrocatalysts affects the activity of the OER. 

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4. Tuning the intrinsic catalytic activities of oxygen-evolution catalysts by doping: a comprehensive review

   https://doi.org/10.1039/D1TA04032D  

   Ede, Sivasankara Rao; Luo, Zhiping (September 2021, Journal of Materials Chemistry A)

   null (Ed.)

   Electrochemical water splitting produces clean hydrogen fuel as one of the pivotal alternative energies to fossil fuels in the near future. However, the anodic oxygen evolution reaction (OER) is a significant bottleneck that curtails large-scale applications of electrochemical water splitting technology, owing to its sluggish reaction kinetics. In the past few decades, various methods have been proposed to improve the OER kinetics. Among them, doping is a simple and efficient method to mold the OER kinetics of a catalyst by incorporating different or hetero atoms into the host lattice. These efforts are vital to design highly efficient OER catalysts for real-world applications. However, the OER mechanism of a doped catalyst varies, depending on the host lattice and the dopant. This review highlights different doping strategies and associated OER mechanisms of state-of-the-art catalysts, including oxides (noble metal oxides, perovskite oxides, spinel oxides, hydroxides and others), non-oxides (metal sulfides, metal selenides, metal phosphides, metal nitrides and metal carbides), and carbon-based catalysts (graphene, carbon nanotubes and others). Fundamental understanding of the doping effects on the OER from combined experimental and theoretical research provides guidelines for designing efficient catalysts. 

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5. Critical Review of Platinum Group Metal-Free Materials for Water Electrolysis: Transition from the Laboratory to the Market : Earth-abundant borides and phosphides as catalysts for sustainable hydrogen production

   https://doi.org/10.1595/205651321X16067419458185  

   Serov, Alexey; Kovnir, Kirill; Shatruk, Michael; Kolen’ko, Yury V. (April 2021, Johnson Matthey Technology Review)

   null (Ed.)

   To combat the global problem of carbon dioxide emissions, hydrogen is the desired energy vector for the transition to environmentally benign fuel cell power. Water electrolysis (WE) is the major technology for sustainable hydrogen production. Despite the use of renewable solar and wind power as sources of electricity, one of the main barriers for the widespread implementation of WE is the scarcity and high cost of platinum group metals (pgms) that are used to catalyse the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Hence, the critical pgm-based catalysts must be replaced with more sustainable alternatives for WE technologies to become commercially viable. This critical review describes the state-of-the-art pgm-free materials used in the WE application, with a major focus on phosphides and borides. Several emerging classes of HER and OER catalysts are reviewed and detailed structure‐property correlations are comprehensively summarised. The influence of the crystallographic and electronic structures, morphology and bulk and surface chemistry of the catalysts on the activity towards OER and HER is discussed. 

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