Bimetallic core-based cuboctahedral core-shell nanoclusters for the formation of hydrogen peroxide (2e- reduction) over water (4e- reduction): role of core metals

A robust single compartment peroxide fuel cell using mesoporous antimony doped tin oxide as the cathode material

To date, metal oxide catalysts have not been explored as cathode materials for robust and high-performance single-compartment H2O2 fuel cells due to significant non-electrochemical disproportionation losses of H2O2 on many metal oxide surfaces. Here, for the first time, we demonstrate an acidic peroxide fuel cell with antimony doped tin oxide as the cathode and widely used Ni foam as the anode material. Our constructed peroxide fuel cell records a superior open circuit potential of nearly 0.82 V and a maximum power density of 0.32 mW cm-2 with high operational stability. The fuel cell performance is further improved by increasing the ionic strength of the electrolyte with the addition of 1 M NaCl, resulting in an increased maximum power density value of 1.1 mW cm-2.

Sn Bulk Phase Doping and Surface Modification on Ti4 O7 for Oxygen Reduction to Hydrogen Peroxide

Developing stable and highly selective two-electron oxygen reduction reaction (2e- ORR) electrocatalysts for producing hydrogen peroxide (H2 O2 ) is considered a major challenge to replace the anthraquinone process and achieve a sustainable green economy. Here, we doped Sn into Ti4 O7 (D-Sn-Ti4 O7 ) by simple polymerization post-calcination method as a high-efficiency 2e- ORR electrocatalyst. In addition, we also applied plain calcination after the grinding method to load Sn on Ti4 O7 (L-Sn-Ti4 O7 ) as a comparison. However, the performance of L-Sn-Ti4 O7 is far inferior to that of the D-Sn-Ti4 O7 . D-Sn-Ti4 O7 exhibits a starting potential of 0.769 V (versus the reversible hydrogen electrode, RHE) and a high H2 O2 selectivity of 95.7 %. Excitingly, the catalyst can maintain a stable current density of 2.43 mA ⋅ cm-2 for 3600 s in our self-made H-type cell, and the cumulative H2 O2 production reaches 359.2 mg ⋅ L-1 within 50,000 s at 0.3 V. The performance of D-Sn-Ti4 O7 is better than that of the non-noble metal 2e- ORR catalysts reported so far. The doping of Sn not only improves the conductivity but also leads to the lattice distortion of Ti4 O7 , further forming more oxygen vacancies and Ti3+ , which greatly improves its 2e- ORR performance compared with the original Ti4 O7 . In contrast, since the Sn on the surface of L-Sn-Ti4 O7 displays a synergistic effect with Tin+ (3≤n≤4) of Ti4 O7 , the active center Tin+ dissociates the O=O bond, making it more inclined to 4e- ORR.

Co-based Catalysts for Selective H2 O2 Electroproduction via 2-electron Oxygen Reduction Reaction

Electrochemical production of hydrogen peroxide (H₂ O₂ ) via two-electron oxygen reduction reaction (ORR) process is emerging as a promising alternative method to the conventional anthraquinone process. To realize high-efficiency H₂ O₂ electrosynthesis, robust and low cost electrocatalysts have been intensively pursued, among which Co-based catalysts attract particular research interests due to the earth-abundance and high selectivity. Here, we provide a comprehensive review on the advancement of Co-based electrocatalyst for H₂ O₂ electroproduction. The fundamental chemistry of 2-electron ORR is discussed firstly for guiding the rational design of electrocatalysts. Subsequently, the development of Co-based electrocatalysts involving nanoparticles, compounds and single atom catalysts is summarized with the focus on active site identification, structure regulation and mechanism understanding. Moreover, the current challenges and future directions of the Co-based electrocatalysts are briefly summarized in this review.

Electrochemical Reactors for Continuous Decentralized H2 O2 Production

The global utilization of H₂ O₂ is currently around 4 million tons per year and is expected to continue to increase in the future. H₂ O₂ is mainly produced by the anthraquinone process, which involves multiple steps in terms of alkylanthraquinone hydrogenation/oxidation in organic solvents and liquid-liquid extraction of H₂ O₂ . The energy-intensive and environmentally unfriendly anthraquinone process does not meet the requirements of sustainable and low-carbon development. The electrocatalytic two-electron (2 e^- ) oxygen reduction reaction (ORR) driven by renewable energy (e.g. solar and wind power) offers a more economical, low-carbon, and greener route to produce H₂ O₂ . However, continuous and decentralized H₂ O₂ electrosynthesis still poses many challenges. This Minireview first summarizes the development of devices for H₂ O₂ electrosynthesis, and then introduces each component, the assembly process, and some optimization strategies.

Manipulating the oxygen reduction reaction pathway on Pt-coordinated motifs

Electrochemical oxygen reduction could proceed via either 4e--pathway toward maximum chemical-to-electric energy conversion or 2e--pathway toward onsite H2O2 production. Bulk Pt catalysts are known as the best monometallic materials catalyzing O2-to-H2O conversion, however, controversies on the reduction product selectivity are noted for atomic dispersed Pt catalysts. Here, we prepare a series of carbon supported Pt single atom catalyst with varied neighboring dopants and Pt site densities to investigate the local coordination environment effect on branching oxygen reduction pathway. Manipulation of 2e- or 4e- reduction pathways is demonstrated through modification of the Pt coordination environment from Pt-C to Pt-N-C and Pt-S-C, giving rise to a controlled H2O2 selectivity from 23.3% to 81.4% and a turnover frequency ratio of H2O2/H2O from 0.30 to 2.67 at 0.4 V versus reversible hydrogen electrode. Energetic analysis suggests both 2e- and 4e- pathways share a common intermediate of *OOH, Pt-C motif favors its dissociative reduction while Pt-S and Pt-N motifs prefer its direct protonation into H2O2. By taking the Pt-N-C catalyst as a stereotype, we further demonstrate that the maximum H2O2 selectivity can be manipulated from 70 to 20% with increasing Pt site density, providing hints for regulating the stepwise oxygen reduction in different application scenarios.

Unraveling the single-atom electrocatalytic activity of transition metal-doped phosphorene

The development of single-atom catalysts (SACs) for chemical reactions of vital importance in the renewable energy sector has emerged as an urgent priority. In this perspective, transition metal-based SACs with monolayer phosphorous (phosphorene) as the supporting material are scrutinized for their electrocatalytic activity towards the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) from first-principle calculations. The detailed screening study has confirmed a breaking of the scaling relationship between the ORR/OER intermediates, resulting in various activity trends across the transition metal series. Groups 9 and 10 transition metal-based SACs are identified as potential catalyst candidates with the platinum single atom offering bifunctional activity for OER and HER with diminished overpotentials. Ambient condition stability analysis of SACs confirmed a different extent of interaction towards oxygen and water compared to pristine phosphorene, suggesting room for improving the stability of phosphorene via chemical functionalization.

Synergistic Pt-WO3 Dual Active Sites to Boost Hydrogen Production from Ammonia Borane

Development of synergistic heterogeneous catalysts with active sites working cooperatively has been a pursuit of chemists. Herein, we report for the first time the fabrication and manipulation of Pt-WO₃ dual-active-sites to boost hydrogen generation from ammonia borane. A combination of DFT calculations, structural characterization, and kinetic (isotopic) analysis reveals that Pt and WO₃ act as the active sites for ammonia borane and H₂O activation, respectively. A trade-off between the promoting effect of WO₃ and the negative effect of decreased Pt binding energy contributes to a volcano-shaped activity, and Pt/CNT-5W delivers a 4-fold increased activity of 710.1 mol_H2·mol_Pt^-1·min^-1. Moreover, WO₃ is suggested to simultaneously act as the sacrificial site that can divert B-containing by-products away from Pt sites against deactivation, yielding an increase from 24% to 68% of the initial activity after five cycles. The strategy demonstrated here could shed a new light on the design and manipulation of dual-active-site catalysts.

A comparative perspective of electrochemical and photochemical approaches for catalytic H2O2 production

Recent advances in the design, preparation, and applications of different catalysts for electrochemical and photochemical H₂O₂ production are summarized, and some invigorating perspectives for future developments are also provided.

Recent advancements in Pt-nanostructure-based electrocatalysts for the oxygen reduction reaction

A comprehensive evaluation of Pt-nanostructure-based electrocatalysts for the oxygen reduction reaction.