Sulfur-modulated isolated NiNx sites toward electrocatalytic hydrogen peroxide generation

Achieving hydrogen peroxide (H2O2) production through the electrocatalytic two-electron (2e−) oxygen reduction reaction (ORR) is a crucial alternative to the energy-intensive anthraquinone process. The competitive four-electron (4e−) ORR pathway, however, limits the selectivity to H2O2. Here, we report the rational design of isolated NiN3S moieties by introducing one sulfur atom into NiNx sites embedded in carbon supports. The sulfur-modified active sites yield a selectivity of nearly 90% for H2O2 generation. Density functional theory calculations indicate that incorporation of sulfur in Ni’s coordination environment, together with oxidation of the active-site motif, weakens the adsorption energy of OOH∗. This weakening of adsorption strengths for a key reaction intermediate in the 2e− pathway increases selectivity toward H2O2. This work provides a promising approach to direct the selectivity of oxygen reduction by modulating the local structure of isolated metal sites. [Display omitted] •Sulfur modulation strategy is reported to tune the structure of isolated metal sites•Sulfur-modulated NiNx moiety could weaken the adsorption energy of OOH∗•NiN3S1 moiety exhibits excellent catalytic selectivity for H2O2 generation Direct electrosynthesis of H2O2 via the two-electron oxygen reduction reaction is a promising alternative to the industrial anthraquinone oxidation process. To boost the desired performance toward H2O2 generation, the electrocatalysts need to possess an optimal binding strength for OOH∗ to suppress the competitive 4e– oxygen reduction reaction pathway. Here, we report a sulfur modulation strategy for isolated metal sites by introducing a sulfur atom into Ni-N4 sites to achieve the desired 2e– oxygen reduction for H2O2 production. The modified NiN3S moieties weaken the adsorption energy of OOH∗ and thus deliver a selectivity of nearly 90% for H2O2 generation, demonstrating that modulation of the local structure for isolated metal sites is a promising approach to tune catalytic performance. A sulfur modulation strategy is developed to regulate the local coordination environment of isolated NiNx sites. The sulfur atom is introduced into the coordinated environment of NiN4 sites, forming an NiN3S1 moiety and showing weakening of the adsorption energy of OOH∗ during the oxygen reduction process, thus increasing the selectivity for electrocatalytic synthesis of H2O2 to nearly 90%.