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Abstract Electrochemical oxygen reduction to hydrogen peroxide (H 2 O 2 ) in acidic media, especially in proton exchange membrane (PEM) electrode assembly reactors, suffers from low selectivity and the lack of low-cost catalysts. Here we present a cation-regulated interfacial engineering approach to promote the H 2 O 2 selectivity (over 80%) under industrial-relevant generation rates (over 400 mA cm −2 ) in strong acidic media using just carbon black catalyst and a small number of alkali metal cations, representing a 25-fold improvement compared to that without cation additives. Our density functional theory simulation suggests a “shielding effect” of alkali metal cations which squeeze away the catalyst/electrolyte interfacial protons and thus prevent further reduction of generated H 2 O 2 to water. A double-PEM solid electrolyte reactor was further developed to realize a continuous, selective (∼90%) and stable (over 500 hours) generation of H 2 O 2 via implementing this cation effect for practical applications. 

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. 

The electrochemical behavior of sulfur-based batteries is intrinsically governed by polysulfide species. Here, we compare the substitutions of selenium and tellurium into polysulfide chains and demonstrate their beneficial impact on the chemistry of lithium–sulfur batteries. While selenium-substituted polysulfides enhance cathode utilization by effectively catalyzing the sulfur/Li 2 S conversion reactions due to the preferential formation of radical intermediates, tellurium-substituted polysulfides improve lithium cycling efficiency by reducing into a passivating interfacial layer on the lithium surface with low Li + -ion diffusion barriers. This unconventional strategy based on “molecular engineering” of polysulfides and exploiting the intrinsic polysulfide shuttle effect is validated by a ten-fold improvement in the cycle life of lean-electrolyte “anode-free” pouch cells. Assembled with no free lithium metal at the anode, the anode-free configuration maximizes the energy density, mitigates the challenges of handling thin lithium foils, and eliminates self-discharge upon cell assembly. The insights generated into the differences between selenium and tellurium chemistries can be applied to benefit a broad range of metal–chalcogen batteries as well as chalcogenide solid electrolytes. 

Selective electrochemical two-electron oxygen reduction is a promising route for renewable and on-site H2O2 generation as an alternative to the anthraquinone process. Herein, we report a high-performance nitrogen-coordinated single-atom Pd electrocatalyst, which is derived from Pd-doped zeolitic imidazolate frameworks (ZIFs) through one-step thermolysis. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with X-ray absorption spectroscopy verifies atomically dispersed Pd atoms on nitrogen-doped carbon (Pd-NC). The single-atom Pd-NC catalyst exhibits excellent electrocatalytic performance for two-electron oxygen reduction to H2O2, which shows ∼95% selectivity toward H2O2 and an unprecedented onset potential of ∼0.8 V versus revisable hydrogen electrode (RHE) in 0.1 M KOH. Density functional theory (DFT) calculations demonstrate that the Pd-N4 catalytic sites thermodynamically prefer *–O bond breaking to O–O bond breaking, corresponding to a high selectivity for H2O2 production. This work provides a deep insight into the understanding of the catalytic process and design of high-performance 2e– ORR catalysts. 

Abstract Oxygen reduction reaction towards hydrogen peroxide (H 2 O 2 ) provides a green alternative route for H 2 O 2 production, but it lacks efficient catalysts to achieve high selectivity and activity simultaneously under industrial-relevant production rates. Here we report a boron-doped carbon (B-C) catalyst which can overcome this activity-selectivity dilemma. Compared to the state-of-the-art oxidized carbon catalyst, B-C catalyst presents enhanced activity (saving more than 210 mV overpotential) under industrial-relevant currents (up to 300 mA cm −2 ) while maintaining high H 2 O 2 selectivity (85–90%). Density-functional theory calculations reveal that the boron dopant site is responsible for high H 2 O 2 activity and selectivity due to low thermodynamic and kinetic barriers. Employed in our porous solid electrolyte reactor, the B-C catalyst demonstrates a direct and continuous generation of pure H 2 O 2 solutions with high selectivity (up to 95%) and high H 2 O 2 partial currents (up to ~400 mA cm −2 ), illustrating the catalyst’s great potential for practical applications in the future.