Single-Atom Co─O4 Sites Embedded in a Defective-Rich Porous Carbon Layer for Efficient H2O2 Electrosynthesis

The production of hydrogen peroxide (H2O2) via the two-electron electrochemical oxygen reduction reaction (2e- ORR) is an essential alteration in the current anthraquinone-based method. Herein, a single-atom Co─O4 electrocatalyst is embedded in a defective and porous graphene-like carbon layer (Co─O4@PC). The Co─O4@PC electrocatalyst shows promising potential in H2O2 electrosynthesis via 2e- ORR, providing a high H2O2 selectivity of 98.8% at 0.6 V and a low onset potential of 0.73 V for generating H2O2. In situ surface-sensitive attenuated total reflection Fourier transform infrared spectra and density functional theory calculations reveal that the electronic and geometric modification of Co─O4 induced by defective carbon sites result in decreased d-band center of Co atoms, providing the optimum adsorption energies of OOH* intermediate. The H-cell and flow cell assembled using Co─O4@PC as the cathode present long-term stability and high efficiency for H2O2 production. Particularly, a high H2O2 production rate of 0.25 mol g-1 cat h-1 at 0.6 V can be obtained by the flow cell. The in situ-generated H2O2 can promote the degradation of rhodamine B and sterilize Staphylococcus aureus via the Fenton process. This work can pave the way for the efficient production of H2O2 by using Co─O4 single atom electrocatalyst and unveil the electrocatalytic mechanism.

Electrosynthesis of Hydrogen Peroxide through Selective Oxygen Reduction: A Carbon Innovation from Active Site Engineering to Device Design

Electrochemical synthesis of hydrogen peroxide (H2 O2 ) through the selective oxygen reduction reaction (ORR) offers a promising alternative to the energy-intensive anthraquinone method, while its success relies largely on the development of efficient electrocatalyst. Currently, carbon-based materials (CMs) are the most widely studied electrocatalysts for electrosynthesis of H2 O2 via ORR due to their low cost, earth abundance, and tunable catalytic properties. To achieve a high 2e- ORR selectivity, great progress is made in promoting the performance of carbon-based electrocatalysts and unveiling their underlying catalytic mechanisms. Here, a comprehensive review in the field is presented by summarizing the recent advances in CMs for H2 O2 production, focusing on the design, fabrication, and mechanism investigations over the catalytic active moieties, where an enhancement effect of defect engineering or heteroatom doping on H2 O2 selectivity is discussed thoroughly. Particularly, the influence of functional groups on CMs for a 2e- -pathway is highlighted. Further, for commercial perspectives, the significance of reactor design for decentralized H2 O2 production is emphasized, bridging the gap between intrinsic catalytic properties and apparent productivity in electrochemical devices. Finally, major challenges and opportunities for the practical electrosynthesis of H2 O2 and future research directions are proposed.

Metal-Organic Layers for Electrocatalysis and Photocatalysis

Metal-organic layers (MOLs) are two-dimensional analogues of metal-organic frameworks (MOFs) with a high aspect ratio and thickness down to a monolayer. Active sites on MOLs are more accessible than those on MOFs thanks to the two-dimensional feature of MOLs, which allows easier chemical modification around the catalytic center. MOLs can also be assembled with other functional materials through surface anchoring sites that can facilitate charge/energy transport through the hybrid material. MOLs are thus quite suitable for interfacial catalysis like electrocatalysis and photocatalysis. In this outlook, we focus on representative progress of constructing unique interfacial sites on MOLs with designer paths for charge separation and energy transfer, as well as cooperative cavities for superior substrate adsorption and activation. We also discuss challenges and potentials in the future development of MOL catalysts and catalysts beyond MOLs.

2D Electrocatalysts for Converting Earth-Abundant Simple Molecules into Value-Added Commodity Chemicals: Recent Progress and Perspectives

The electrocatalytic conversion of earth-abundant simple molecules into value-added commodity chemicals can transform current chemical production regimes with enormous socioeconomic and environmental benefits. For these applications, 2D electrocatalysts have emerged as a new class of high-performance electrocatalyst with massive forward-looking potential. Recent advances in 2D electrocatalysts are reviewed for emerging applications that utilize naturally existing H₂ O, N₂ , O₂ , Cl^- (seawater) and CH₄ (natural gas) as reactants for nitrogen reduction (N₂ → NH₃ ), two-electron oxygen reduction (O₂ → H₂ O₂ ), chlorine evolution (Cl^- → Cl₂ ), and methane partial oxidation (CH₄ → CH₃ OH) reactions to generate NH₃ , H₂ O₂ , Cl₂ , and CH₃ OH. The unique 2D features and effective approaches that take advantage of such features to create high-performance 2D electrocatalysts are articulated with emphasis. To benefit the readers and expedite future progress, the challenges facing the future development of 2D electrocatalysts for each of the above reactions and the related perspectives are provided.

Carbon-based dots for the electrochemical production of hydrogen peroxide

Graphene/carbon-based dot nanohybrids were prepared by the ultrasonic exfoliation of natural graphite in the presence of single-layer carbon based dots, and used for the electrochemical production of hydrogen peroxide.

Cooperative Stabilization of the [Pyridinium-CO2-Co] Adduct on a Metal-Organic Layer Enhances Electrocatalytic CO2 Reduction

Pyridinium has been shown to be a cocatalyst for the electrochemical reduction of CO₂ on metal and semiconductor electrodes, but its exact role has been difficult to elucidate. In this work, we create cooperative cobalt-protoporphyrin (CoPP) and pyridine/pyridinium (py/pyH⁺) catalytic sites on metal-organic layers (MOLs) for an electrocatalytic CO₂ reduction reaction (CO₂RR). Constructed from [Hf₆(μ₃-O)₄(μ₃-OH)₄(HCO₂)₆] secondary building units (SBUs) and terpyridine-based tricarboxylate ligands, the MOL was postsynthetically functionalized with CoPP via carboxylate exchange with formate capping groups. The CoPP group and the pyridinium (pyH⁺) moiety on the MOL coactivate CO₂ by forming the [pyH⁺-^-O₂C-CoPP] adduct, which enhances the CO₂RR and suppresses hydrogen evolution to afford a high CO/H₂ selectivity of 11.8. Cooperative stabilization of the [pyH⁺-^-O₂C-CoPP] intermediate led to a catalytic current density of 1314 mA/mgCo for CO production at -0.86 V_RHE, which corresponds to a turnover frequency of 0.4 s^-1.