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1. Discovery of LaAlO3 as an efficient catalyst for two-electron water electrolysis towards hydrogen peroxide

   https://doi.org/10.1038/s41467-022-34884-4  

   Baek, Jihyun ; Jin, Qiu ; Johnson, Nathan Scott ; Jiang, Yue ; Ning, Rui ; Mehta, Apurva ; Siahrostami, Samira ; Zheng, Xiaolin ( November 2022 , Nature Communications)

   Electrochemical two-electron water oxidation reaction (2e-WOR) has drawn significant attention as a promising process to achieve the continuous on-site production of hydrogen peroxide (H₂O₂). However, compared to the cathodic H₂O₂generation, the anodic 2e-WOR is more challenging to establish catalysts due to the severe oxidizing environment. In this study, we combine density functional theory (DFT) calculations with experiments to discover a stable and efficient perovskite catalyst for the anodic 2e-WOR. Our theoretical screening efforts identify LaAlO₃perovskite as a stable, active, and selective candidate for catalyzing 2e-WOR. Our experimental results verify that LaAlO₃achieves an overpotential of 510 mV at 10 mA cm⁻²in 4 M K₂CO₃/KHCO₃, lower than those of many reported metal oxide catalysts. In addition, LaAlO₃maintains a stable H₂O₂Faradaic efficiency with only a 3% decrease after 3 h at 2.7 V vs. RHE. This computation-experiment synergistic approach introduces another effective direction to discover promising catalysts for the harsh anodic 2e-WOR towards H₂O₂.

    

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2. Computational Discovery of Active and Selective Metal‐Nitrogen‐Graphene Catalysts for Electrooxidation of Water to H 2 O 2

   https://doi.org/10.1002/cctc.202300055  

   Chaudhary, Payal ; Evazzade, Iman ; Belosludov, Rodion ; Alexandrov, Vitaly ( April 2023 , ChemCatChem)

   A direct electrosynthesis of H₂O₂from either O₂or H₂O is an attractive strategy to replace the energy‐intensive industrial anthraquinone process. Two‐electron water oxidation reaction (2e‐WOR) offers several advantages over the oxygen reduction reaction such as better mass transfer due to the absence of gas‐phase reactants. However, 2e‐WOR is a more challenging and less studied process with only a handful of metal oxides exhibiting reasonable activity/selectivity properties. Herein, we employ density‐functional‐theory calculations to screen a variety of metal‐nitrogen‐graphene structures for 2e‐WOR. As a consequence of scaling between the adsorption energies of reaction intermediates, we determine a linear relation between selectivities for the first and second reaction steps of 2e‐WOR, viz. that if selectivity toward adsorbed OH is improved, then selectivity toward H₂O₂at the subsequent step is decreased. We also find that selectivity and activity are linearly scaled in such a way that a higher activity (i. e., a lower overpotential) leads to a lower selectivity for the H₂O₂formation step. Based on the obtained results several chemistries, e. g., containing NiN_x−C moieties, are predicted to rival the best‐performing metal oxides such as ZnO and CaSnO₃in terms of combination of their activity/selectivity characteristics for 2e‐WOR.

    

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3. 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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4. Stable and selective electrosynthesis of hydrogen peroxide and the electro-Fenton process on CoSe 2 polymorph catalysts

   https://doi.org/10.1039/D0EE01925A  

   Sheng, Hongyuan ; Janes, Aurora N. ; Ross, R. Dominic ; Kaiman, Dave ; Huang, Jinzhen ; Song, Bo ; Schmidt, J. R. ; Jin, Song ( November 2020 , Energy & Environmental Science)

   null (Ed.)

   Electrochemical synthesis of hydrogen peroxide (H 2 O 2 ) in acidic solution can enable the electro-Fenton process for decentralized environmental remediation, but robust and inexpensive electrocatalysts for the selective two-electron oxygen reduction reaction (2e − ORR) are lacking. Here, we present a joint computational/experimental study that shows both structural polymorphs of earth-abundant cobalt diselenide (orthorhombic o -CoSe 2 and cubic c -CoSe 2 ) are stable against surface oxidation and catalyst leaching due to the weak O* binding to Se sites, are highly active and selective for the 2e − ORR, and deliver higher kinetic current densities for H 2 O 2 production than the state-of-the-art noble metal or single-atom catalysts in acidic solution. o -CoSe 2 nanowires directly grown on carbon paper electrodes allow for the steady bulk electrosynthesis of H 2 O 2 in 0.05 M H 2 SO 4 with a practically useful accumulated concentration of 547 ppm, the highest among the reported 2e − ORR catalysts in acidic solution. Such efficient and stable H 2 O 2 electrogeneration further enables the effective electro-Fenton process for model organic pollutant degradation. 

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5. Reduction-induced CO dissociation by a [Mn(bpy)(CO) 4 ][SbF 6 ] complex and its relevance in electrocatalytic CO 2 reduction

   https://doi.org/10.1039/c9dt04150h  

   Kuo, Hsin-Ya ; Tignor, Steven E. ; Lee, Tia S. ; Ni, Danrui ; Park, James Eujin ; Scholes, Gregory D. ; Bocarsly, Andrew B. ( January 2020 , Dalton Transactions)

   [Mn(bpy)(CO) 3 Br] is recognized as a benchmark electrocatalyst for CO 2 reduction to CO, with the doubly reduced [Mn(bpy)(CO) 3 ] − proposed to be the active species in the catalytic mechanism. The reaction of this intermediate with CO 2 and two protons is expected to produce the tetracarbonyl cation, [Mn(bpy)(CO) 4 ] + , thereby closing the catalytic cycle. However, this species has not been experimentally observed. In this study, [Mn(bpy)(CO) 4 ][SbF 6 ] ( 1 ) was directly synthesized and found to be an efficient electrocatalyst for the reduction of CO 2 to CO in the presence of H 2 O. Complex 1 was characterized using X-ray crystallography as well as IR and UV-Vis spectroscopy. The redox activity of 1 was determined using cyclic voltammetry and compared with that of benchmark manganese complexes, e.g. , [Mn(bpy)(CO) 3 Br] ( 2 ) and [Mn(bpy)(CO) 3 (MeCN)][PF 6 ] ( 3 ). Infrared spectroscopic analyses indicated that CO dissociation occurs after a single-electron reduction of complex 1 , producing a [Mn(bpy)(CO) 3 (MeCN)] + species. Complex 1 was experimentally verified as both a precatalyst and an on-cycle intermediate in homogeneous Mn-based electrocatalytic CO 2 reduction. 

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