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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. 

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. 

Changes in the local atomic arrangement in a crystal caused by lattice-mismatch-induced strain can efficiently regulate the performance of electrocatalysts for zinc–air batteries (ZABs) in many manners, mainly due to modulated electronic structure configurations that affect the adsorption energies for oxygen-intermediates formed during oxygen reduction and evolution reactions (ORR and OER). However, the application of strain engineering in electrocatalysis has been limited by the strain relaxation caused by structural instability such as dissolution and destruction, leading to insufficient durability towards the ORR/OER. Herein, we propose a doping strategy to modulate the phase transition and formation of self-supported cobalt fluoride–sulfide (CoFS) nanoporous films using a low amount of copper (Cu) as a dopant. This well-defined Cu–CoFS heterostructure overcomes the obstacle of structural instability. Our study of the proposed Cu–CoFS also helps establish the structure–property relationship of strained electrocatalysts by unraveling the role of local strain in regulating the electronic structure of the catalyst. As a proof-of-concept, the Cu–CoFS electrocatalyst with doping-modulated strain exhibited superior onset potentials of 0.91 V and 1.49 V for the ORR and OER, respectively, surpassing commercial Pt/C@RuO 2 and benchmarking non-platinum group metal (non-PGM) catalysts. ZABs with the Cu–CoFS catalyst delivered excellent charge/discharge cycling performance with an extremely low voltage gap of 0.5 V at a current density of 10 mA cm −2 and successively 0.93 V at a high current density of 100 mA cm −2 and afforded an outstanding peak power density of 255 mW cm −2 . 

Proton-exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are promising power sources from portable electronic devices to vehicles. The high-cost issue of these low-temperature fuel cells can be primarily addressed by using platinum-group metal (PGM)-free oxygen reduction reaction (ORR) catalysts, in particular atomically dispersed metal–nitrogen–carbon (M–N–C, M = Fe, Co, Mn). Furthermore, a significant advantage of M–N–C catalysts is their superior methanol tolerance over Pt, which can mitigate the methanol cross-over effect and offer great potential of using a higher concentration of methanol in DMFCs. Here, we investigated the ORR catalytic properties of M–N–C catalysts in methanol-containing acidic electrolytes via experiments and density functional theory (DFT) calculations. FeN 4 sites demonstrated the highest methanol tolerance ability when compared to metal-free pyridinic N, CoN 4 , and MnN 4 active sites. The methanol adsorption on MN 4 sites is even strengthened when electrode potentials are applied during the ORR. The negative influence of methanol adsorption becomes significant for methanol concentrations higher than 2.0 M. However, the methanol adsorption does not affect the 4e − ORR pathway or chemically destroy the FeN 4 sites. The understanding of the methanol-induced ORR activity loss guides the design of promising M–N–C cathode catalyst in DMFCs. Accordingly, we developed a dual-metal site Fe/Co–N–C catalyst through a combined chemical-doping and adsorption strategy. Instead of generating a possible synergistic effect, the introduced Co atoms in the first doping step act as “scissors” for Zn removal in metal–organic frameworks (MOFs), which is crucial for modifying the porosity of the catalyst and providing more defects for stabilizing the active FeN 4 sites generated in the second adsorption step. The Fe/Co–N–C catalyst significantly improved the ORR catalytic activity and delivered remarkably enhanced peak power densities ( i.e. , 502 and 135 mW cm −2 ) under H 2 –air and methanol–air conditions, respectively, representing the best performance for both types of fuel cells. Notably, the fundamental understanding of methanol tolerance, along with the encouraging DMFC performance, will open an avenue for the potential application of atomically dispersed M–N–C catalysts in other direct alcohol or ammonia fuel cells.