Hydrogen peroxide (H2O2) and formate are important chemicals used in various chemical manufacturing industries. One promising approach for the simultaneous production of these chemicals is coupling anodic two‐electron water oxidation with cathodic CO2 reduction in an electrolyzer using nonprecious bifunctional electrocatalysts. Herein, we report an innovative hybrid electrosynthesis strategy using Zn‐doped SnO2 (Zn/SnO2) nanodots as bifunctional redox electrocatalysts to achieve Faradaic efficiencies of 80.6 % and 92.2 % for H2O2 and formate coproduction, respectively, along with excellent stability for at least 60 h at a current density of ≈150 mA cm−2. Through a combination of physicochemical characterizations, including operando attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), isotope labeling mass spectrometry (MS)/1H NMR and quasi‐in situ electron paramagnetic resonance (EPR), with density functional theory (DFT) calculations, we discovered that the Zn dopant facilitates the coupling of *OH intermediates to promote H2O2 production and optimizes the adsorption of *OCHO intermediates to accelerate formate formation. Our findings offer new insights into designing more efficient bifunctional electrocatalyst‐based pair‐electrosynthesis system for the coproduction of H2O2 and formate feedstocks.

PtNi nanoalloys have demonstrated electrocatalysis superior to that of benchmark Pt/C catalysts for the oxygen reduction reaction (ORR), yet the underlying mechanisms remain underexplored. Herein, a PtNi/NC catalyst comprising PtNi nanoparticles (∼5.2 nm in size) dispersed on N-doped carbon frameworks was prepared using a simple pyrolysis strategy. Benefiting from the individual components and a hierarchical structure, the PtNi/NC catalyst exhibited outstanding ORR activity and stability (E 1/2 = 0.82 V vs RHE and 8 mV negative shift after 20000 cycles), outperforming a commercial 20 wt % Pt/C catalyst (E 1/2 = 0.81 V and 32 mV negative shift). A prototype zinc–air battery constructed using PtNi/NC as the air electrode catalyst achieved highly enhanced electrochemical performance, outperforming a battery constructed using Pt/C as the ORR catalyst. Density functional theory calculations revealed that the improved ORR activity of the PtNi nanoalloys originated from charge redistribution with a suitable metal d-band center to promote the formation of the ORR intermediates.

No abstract

The commercialization of zinc–air batteries (ZABs) and many types of fuel cells hinges on the discovery of non-precious metal catalysts with high activity and durability for the oxygen reduction reaction (ORR). Herein, we describe a simple and scalable l-alanine-assisted thermal pyrolysis strategy [utilizing l-alanine, urea, Ketjenblack carbon (KB), and CoCl2 as precursors] that yielded a Co@N–C/N–KB catalyst with outstanding ORR performance in alkaline media. The addition of l-alanine in the pyrolysis-step increased the proportion of pyridinic-N + graphitic-N in the Co@N–C/N–KB catalyst, with highly conductive KB-promoting electron transfer kinetics during ORR. These attributes, together with the hierarchical porosity of the catalyst [presence of micropores, mesopores (dominant), and macropores], gave Co@N–C/N–KB an onset potential of 0.91 V vs RHE, a half-wave potential of 0.84 V vs RHE, a limiting current density of −5.86 mA cm–2, a Tafel slope of 63.7 mV dec–1, and an excellent durability and methanol tolerance (superior to a commercial 20 wt % Pt/C catalyst in almost all these aspects). A ZAB constructed with Co@N–C/N–KB as the cathode catalyst delivered an impressive open-circuit voltage of 1.519 V, a high power density of 204.5 mW cm–2, an energy density up to 790 mA h gZn –1, and very stable operation with charge–discharge cycling, thus offering great promise for practical devices.

Herein, a simple two-step synthetic method was developed for the synthesis of NiFe 2 O 4 nano-microrods supported on Ketjenblack carbon (NiFe 2 O 4 /KB). A sodium tartrate-assisted hydrothermal method was employed for the synthesis of a NiFe-MOF/KB precursor, which was then pyrolyzed under N 2 at 500 °C to yield NiFe 2 O 4 /KB. Benefiting from the presence of high-valence Ni 3+ and Fe 3+ , high conductivity, and a large electrochemically active surface area, NiFe 2 O 4 /KB delivered outstanding OER electrocatalytic performance under alkaline conditions, including a very low overpotential of 258 mV (vs RHE) at 10 mA cm −2 , a small Tafel slope of 43.01 mV dec −1 , and excellent durability in 1.0 M KOH. Density functional theory calculations verified the superior alkaline OER electrocatalytic activity of NiFe 2 O 4 to IrO 2 . While both catalysts possessed a similar metallic ground state, NiFe 2 O 4 offered a lower energy barrier in the rate-determining OER step (*OOH → O 2 ) compared to IrO 2 , resulting in faster OER kinetics.