Propylene oxide (PO) is a crucial feedstock in the plastic industry. The direct epoxidation of propylene using O 2 is considered to be the most promising means of producing PO, but it remains challenging. Here, we report on an integrated photo-electro-heterogeneous catalytic system for propylene epoxidation with O 2 . Bismuth vanadate (or TiO 2 ) photocatalyst and Co-based electrocatalyst produce H 2 O 2 and titanium silicalite-1 heterogeneous catalyst epoxidises propylene to PO with the in situ generated H 2 O 2 . This system enables PO production with O 2 as the sole oxidising agent under light irradiation without using H 2 , a sacri cial agent, or external bias. It stably produces PO for 24 h with high selectivity (≥ 98%) under ambient conditions. These results demonstrate the potential of this new catalytic system to produce chemical compounds in an environmentally benign manner.

Lignin is a major component of lignocellulosic biomass. Although it is highly recalcitrant to break down, it is a very abundant natural source of valuable aromatic carbons. Thus, the effective valorisation of lignin is crucial for realising a sustainable biorefinery chain. Here, we report a compartmented photo-electro-biochemical system for unassisted, selective, and stable lignin valorisation, in which a TiO2 photocatalyst, an atomically dispersed Co-based electrocatalyst, and a biocatalyst (lignin peroxidase isozyme H8, horseradish peroxidase) are integrated, such that each system is separated using Nafion and cellulose membranes. This cell design enables lignin valorisation upon irradiation with sunlight without the need for any additional bias or sacrificial agent and allows the protection of the biocatalyst from enzyme-damaging elements, such as reactive radicals, gas bubbles, and light. The photo-electro-biochemical system is able to catalyse lignin depolymerisation with a 98.7% selectivity and polymerisation with a 73.3% yield using coniferyl alcohol, a lignin monomer.

No abstract

The importance of hydrogen peroxide (H 2 O 2 ) continues to grow globally. Deriving the oxygen reduction reaction (ORR) toward the 2epathway to form H 2 O 2 is crucial for high H 2 O 2 productivity. However, most selective electrocatalysts following the 2epathway comprise carbon-containing organic materials with intrinsically low stability, thereby limiting their commercial applicability. Herein, layered double hydroxides (LDHs) are used as inorganic matrices for the first time. The LDH catalyst developed herein exhibits near-100% 2e -ORR selectivity and stably produces H 2 O 2 with a concentration of ≈108.2 mm cm -2 photoanode in 24 h in a two-compartment system (with a photoanode) with a solar-to-chemical conversion efficiency of ≈3.24%, the highest among all reported systems. Density functional theory calculations show that 2e -ORR selectivity is promoted by atomically dispersed cobalt atoms in (012) planes of the LDH catalyst, while a free energy gap between the * O and OOHstates is an important factor.

Hydrogen peroxide (H2O2) is a valuable chemical that has been used in a wide range of applications. Currently, H2O2 production relies predominantly on the anthraquinone process, which is energy-intensive and non-ecofriendly. The photoelectrochemical two-electron O2 reduction reaction (2e– ORR) and 2e– water oxidation reaction (2e– WOR) have recently emerged as promising alternatives to produce H2O2 in a bias-free, cost-effective, and environmentally benign manner. In this Perspective, we overview photoelectrochemical routes to H2O2 production and its in situ application for valuable chemical synthesis. We discuss the design principles needed for achieving a bias-free photoelectrochemical H2O2 synthesis and introduce the concept of single and dual constructions, with notable examples of each one. We benchmark the solar-to-chemical conversion efficiencies of photoelectrochemical H2O2 synthesis cells. Further, we present the application of photoelectrochemically produced H2O2 for in situ green chemical synthesis. Finally, we provide future perspectives on this emerging field, discussing its main limitations and targets for further development, including high performance, stability of produced H2O2, and practical viability.