Lei Han

Hydrogen peroxide (H2O2) has a wide range of important applications in various fields including chemical industry, environmental remediation, and sustainable energy conversion/storage. Nevertheless, the stark disconnect between today's huge market demand and the historical unsustainability of the currently-used industrial anthraquinone-based production process is promoting extensive research on the development of efficient, energy-saving and sustainable methods for H2O2 production. Among several sustainable strategies, H2O2 production via electrochemical and photochemical routes has shown particular appeal, because only water, O2, and solar energy/electricity are involved during the whole process. In the past few years, considerable efforts have been devoted to the development of advanced electrocatalysts and photocatalysts for efficient and scalable H2O2 production with high efficiency and stability. In this review, we compare and contrast the two distinct yet inherently closely linked catalytic processes, before we detail recent advances in the design, preparation, and applications of different H2O2 catalyst systems from the viewpoint of electrochemical and photochemical approaches. We close with a balanced perspective on remaining future scientific and technical challenges and opportunities.

Novel Ni–Co-Prussian-blue-analog nano­cages consisting of pyramid-like walls were prepared via a facile chemical etching process with ammonia at room temperature. After annealing in air, the derived Ni–Co mixed oxide nanocages exhibit enhanced electrocatalytic activity and excellent stability toward the oxygen-evolution reaction. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract Heteroatom doped atomically dispersed Fe 1 ‐NC catalysts have been found to show excellent activity toward oxygen reduction reaction (ORR). However, the origin of the enhanced activity is still controversial because the structure‐function relationship governing the enhancement remains elusive. Herein, sulfur( S )‐doped Fe 1 ‐NC catalyst was obtained as a model, which displays a superior activity for ORR towards the traditional Fe‐NC materials. 57 Fe Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy revealed that incorporation of S in the second coordination sphere of Fe 1 ‐NC can induce the transition of spin polarization configuration. Operando 57 Fe Mössbauer spectra definitively identified the low spin single‐Fe 3+ ‐atom of C‐FeN 4 ‐S moiety as the active site for ORR. Moreover, DFT calculations unveiled that lower spin state of the Fe center after the S doping promotes OH* desorption process. This work elucidates the underlying mechanisms towards S doping for enhancing ORR activity, and paves a way to investigate the function of broader heteroatom doped Fe 1 ‐NC catalysts to offer a general guideline for spin‐state‐determined ORR.

Carbon-based materials are considered to be active for electrochemical oxygen reduction reaction (ORR) to hydrogen peroxide (H2O2) production. Nevertheless, less attention is paid to the investigation of the influence of in-plane carbon lattice defect on the catalytic activity and selectivity toward ORR. In the present work, graphene precursors were prepared from oxo-functionalized graphene (oxo-G) and graphene oxide (GO) with H2O2 hydrothermal treatment, respectively. Statistical Raman spectroscopy (SRS) analysis demonstrated the increased in-plane carbon lattice defect density in the order of oxo-G, oxo-G/H2O2, GO, GO/H2O2. Furthermore, nitrogen-doped graphene materials were prepared through ammonium hydroxide hydrothermal treatment of those graphene precursors. Rotating ring-disk electrode (RRDE) results indicate that the nitrogen-doped graphene derived from oxo-G with lowest in-plane carbon lattice defects exhibited the highest H2O2 selectivity of >82% in 0.1 M KOH. Moreover, a high H2O2 production rate of 224.8 mmol gcatalyst–1 h–1 could be achieved at 0.2 VRHE in H-cell with faradaic efficiency of >43.6%. Our work provides insights for the design and synthesis of carbon-based electrocatalysts for H2O2 production.