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.

/pdf/a-comparative-perspective-of-electrochemical-and-23uifuhnie.pdf

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

Electrochemical two-electron water oxidation is a promising route for renewable and on-site H2O2 generation as an alternative to the anthraquinone process. However, it is currently restricted by low selectivity due to strong competition from the traditional four-electron oxygen evolution reaction, as well as large overpotential and low production rates. Here we report an interfacial engineering approach, where by coating the catalyst with hydrophobic polymers we confine in situ produced O2 gas to tune the water oxidation reaction pathway. Using carbon catalysts as a model system, we show a significant increase of the intrinsic H2O-to-H2O2 selectivity and activity compared to that of the pristine catalyst. The maximal H2O2 Faradaic efficiency was enhanced by sixfold to 66% with an overpotential of 640 mV, under which a H2O2 production rate of 23.4 µmol min−1 cm−2 (75.2 mA cm−2 partial current) was achieved. This approach was successfully extended to nickel metal, demonstrating the wide applicability of our local gas confinement concept. Electrochemical 2e− water oxidation is a promising route for renewable H2O2 production but it suffers from low selectivity due to the competing 4e− process. Here the authors demonstrate an interfacial engineering approach where the catalyst is coated with a hydrophobic polymer to confine in situ produced O2 and promote the 2e− pathway.

/pdf/confined-local-oxygen-gas-promotes-electrochemical-water-3121xhe647.pdf

Confined local oxygen gas promotes electrochemical water oxidation to hydrogen peroxide

Hydrogen peroxide is a valuable chemical oxidant with a wide range of applications in a variety of industrial processes, especially in water sanitization. Electrochemical synthesis of hydrogen pero...

/pdf/a-review-on-challenges-and-successes-in-atomic-scale-design-1r50s80k9i.pdf

A Review on Challenges and Successes in Atomic-Scale Design of Catalysts for Electrochemical Synthesis of Hydrogen Peroxide

Global development has been heavily reliant on the overexploitation of natural resources since the Industrial Revolution. With the extensive use of fossil fuels, deforestation, and other forms of land-use change, anthropogenic activities have contributed to the ever-increasing concentrations of greenhouse gases (GHGs) in the atmosphere, causing global climate change. In response to the worsening global climate change, achieving carbon neutrality by 2050 is the most pressing task on the planet. To this end, it is of utmost importance and a significant challenge to reform the current production systems to reduce GHG emissions and promote the capture of CO2 from the atmosphere. Herein, we review innovative technologies that offer solutions achieving carbon (C) neutrality and sustainable development, including those for renewable energy production, food system transformation, waste valorization, C sink conservation, and C-negative manufacturing. The wealth of knowledge disseminated in this review could inspire the global community and drive the further development of innovative technologies to mitigate climate change and sustainably support human activities.

Technologies and perspectives for achieving carbon neutrality

Solar energy-assisted water oxidative hydrogen peroxide (H2O2) production on an anode combined with H2 production on a cathode increases the value of solar water splitting, but the challenge of the...

Near-Complete Suppression of Oxygen Evolution for Photoelectrochemical H2O Oxidative H2O2 Synthesis

Electrochemical synthesis of hydrogen peroxide (H2O2) via two-electron water oxidation reaction (2e-WOR) is an ideal process for delocalized production for water cleaning and other applications. Pr...

/pdf/zno-as-an-active-and-selective-catalyst-for-electrochemical-2tq4byqrwg.pdf

ZnO As an Active and Selective Catalyst for Electrochemical Water Oxidation to Hydrogen Peroxide

The oxygen reduction reaction (ORR) is the key bottleneck in the performance of fuel cells So far, the most active and stable electrocatalysts for the reaction are based on Pt group metals Transition metal oxides (TMOs) constitute an alternative class of materials for achieving operational stability under oxidizing conditions Unfortunately, TMOs are generally found to be less active than Pt Here, we identify two reasons why it is difficult to find TMOs with a high ORR activity The first is that TMO surfaces consistently bind oxygen atoms more weakly than transition metals do This makes the breaking of the O–O bond rate-determining for the broad range of TMO surfaces investigated here The second is that electric field effects are stronger at TMO surfaces, which further makes O–O bond breaking difficult To validate the predictions and ascertain their generalizability for TMOs, we report experimental ORR catalyst screening for 7,798 unique TMO compositions that generally exhibit activity well below that of Pt Transition metal oxides constitute a promising class of catalysts for the oxygen reduction reaction, but they are found generally to be less active than Pt Now, computational analyses and high-throughput experiments are used to understand the reasons behind the lower activity, and strategies to improve them are proposed

Analysis of the limitations in the oxygen reduction activity of transition metal oxide surfaces

In this work, we develop a new microkinetic model for the oxygen reduction reaction (ORR) which incorporates field effects into the established computational hydrogen electrode model. We find that ...

Electric Field Effects in Oxygen Reduction Kinetics:Rationalizing pH Dependence at the Pt(111), Au(111), and Au(100) Electrodes

Stability and Activity of Cobalt Antimonate for Oxygen Reduction in Strong Acid

On-site hydrogen peroxide (H2O2) production via electrochemical methods, such as two-electron water oxidation reaction (2e-WOR) and two-electron oxygen reduction reaction (2e-ORR), offer an attractive alternative to the anthraquinone oxidation (AO) process. However, for 2e-WOR and 2e-ORR to hold any industrial relevance, inexpensive, stable, highly efficient, selective, and environmentally benign electrocatalysts must be developed. Designing a catalyst to meet such an extensive criterion remains a challenge. Single-atom catalysts (SACs), combining the benefits of heterogenous and homogenous catalysis, have drawn immense attention due to their distinguished catalytic performance. Ergo, we aim towards the exploration of a bifunctional SAC material capable of catalyzing the 2e-WOR and 2e-ORR to produce H2O2. Through density functional theory (DFT) calculations we investigate the catalytic activity, selectivity, and stability of SnO2-supported SACs. Considering 16 different single metal atoms, various promising candidates were identified. Particularly, Mn, Ti and Fe were found to be markedly active and selective 2e-WOR catalysts and W for the 2e-ORR. This work highlights the immense potential of bifunctional systems; a route towards increasing H2O2 yields while simultaneously minimizing manufacturing complexity and cost.

Sara R. Kelly

Papers

ZnO As an Active and Selective Catalyst for Electrochemical Water Oxidation to Hydrogen Peroxide

Analysis of the limitations in the oxygen reduction activity of transition metal oxide surfaces

Electric Field Effects in Oxygen Reduction Kinetics:Rationalizing pH Dependence at the Pt(111), Au(111), and Au(100) Electrodes

Stability and Activity of Cobalt Antimonate for Oxygen Reduction in Strong Acid

SnO2-supported single metal atoms: a bifunctional catalyst for the electrochemical synthesis of H2O2