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1. Voltage-Driven Molecular Photoelectrocatalysis of Water Oxidation

   https://doi.org/10.1021/jacs.4c10896  

   Barman, Koushik; Askarova, Gaukhar; Somni, Rahul; Hu, Guoxiang; Mirkin, Michael V (October 2024, Journal of the American Chemical Society)
2. Relevance of Chemical vs. Electrochemical Oxidation of Tunable Carbene Iridium Complexes for Catalytic Water Oxidation: Relevance of Chemical vs. Electrochemical Oxidation of Tunable Carbene Iridium Complexes for Catalytic Water Oxidation

   https://doi.org/10.1002/ejic.202000090  

   Olivares, Marta; van der Ham, Cornelis J. M.; Mdluli, Velabo; Schmidtendorf, Markus; Müller-Bunz, Helge; Verhoeven, Tiny W. G. M.; Li, Mo; Niemantsverdriet, J. W. Hans; Hetterscheid, Dennis G. H.; Bernhard, Stefan; et al (March 2020, European Journal of Inorganic Chemistry)
3. A polymeric hydrogel electrocatalyst for direct water oxidation

   https://doi.org/10.1038/s41467-023-36532-x  

   Pei, Zengxia; Tan, Hao; Gu, Jinxing; Lu, Linguo; Zeng, Xin; Zhang, Tianqi; Wang, Cheng; Ding, Luyao; Cullen, Patrick J.; Chen, Zhongfang; et al (December 2023, Nature Communications)

   Abstract Metal-free electrocatalysts represent a main branch of active materials for oxygen evolution reaction (OER), but they excessively rely on functionalized conjugated carbon materials, which substantially restricts the screening of potential efficient carbonaceous electrocatalysts. Herein, we demonstrate that a mesostructured polyacrylate hydrogel can afford an unexpected and exceptional OER activity – on par with that of benchmark IrO 2 catalyst in alkaline electrolyte, together with a high durability and good adaptability in various pH environments. Combined theoretical and electrokinetic studies reveal that the positively charged carbon atoms within the carboxylate units are intrinsically active toward OER, and spectroscopic operando characterizations also identify the fingerprint superoxide intermediate generated on the polymeric hydrogel backbone. This work expands the scope of metal-free materials for OER by providing a new class of polymeric hydrogel electrocatalysts with huge extension potentials. 

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4. 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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5. CO2/carbonate-mediated electrochemical water oxidation to hydrogen peroxide

   https://doi.org/10.1038/s41467-022-30251-5  

   Fan, Lei; Bai, Xiaowan; Xia, Chuan; Zhang, Xiao; Zhao, Xunhua; Xia, Yang; Wu, Zhen-Yu; Lu, Yingying; Liu, Yuanyue; Wang, Haotian (December 2022, Nature Communications)

   Abstract Electrochemical water oxidation reaction (WOR) to hydrogen peroxide (H 2 O 2 ) via a 2e − pathway provides a sustainable H 2 O 2 synthetic route, but is challenged by the traditional 4e − counterpart of oxygen evolution. Here we report a CO 2 /carbonate mediation approach to steering the WOR pathway from 4e − to 2e − . Using fluorine-doped tin oxide electrode in carbonate solutions, we achieved high H 2 O 2 selectivity of up to 87%, and delivered unprecedented H 2 O 2 partial currents of up to 1.3 A cm −2 , which represents orders of magnitude improvement compared to literature. Molecular dynamics simulations, coupled with electron paramagnetic resonance and isotope labeling experiments, suggested that carbonate mediates the WOR pathway to H 2 O 2 through the formation of carbonate radical and percarbonate intermediates. The high selectivity, industrial-relevant activity, and good durability open up practical opportunities for delocalized H 2 O 2 production. 

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