Photo-excitation of certain semiconductors can lead to the production of reactive oxygen species that can inactivate microorganisms. The mechanisms involved are reviewed, along with two important applications. The first is the use of photocatalysis to enhance the solar disinfection of water. It is estimated that 750 million people do not have accessed to an improved source for drinking and many more rely on sources that are not safe. If one can utilize photocatalysis to enhance the solar disinfection of water and provide an inexpensive, simple method of water disinfection, then it could help reduce the risk of waterborne disease. The second application is the use of photocatalytic coatings to combat healthcare associated infections. Two challenges are considered, i.e., the use of photocatalytic coatings to give “self-disinfecting” surfaces to reduce the risk of transmission of infection via environmental surfaces, and the use of photocatalytic coatings for the decontamination and disinfection of medical devices. In the final section, the development of novel photocatalytic materials for use in disinfection applications is reviewed, taking account of materials, developed for other photocatalytic applications, but which may be transferable for disinfection purposes.

The development of suitable approaches for the synthesis of ultrathin transition-metal dichalcogenide (TMD) catalysts is required to engineer phases, intercoupling between different phases, in-plane defects, and edges and hence maximize their catalytic performance for hydrogen production. In this work, we report a simple one-step hydrothermal approach for the synthesis of a three-dimensional (3D) network of self-assembled metallic MoS₂/MoO₃ nanosheets, using α-MoO₃ and thiourea (TU) as the Mo and S precursors, respectively. A systematic structural/property relationship study, while varying the precursors’ molar concentration ratios (TU/MoO₃) and reaction temperatures (T_R), revealed a kinetically controlled regime, in hydrothermal synthesis, that enabled the formation of ultrathin branched MoS₂/MoO₃ nanosheets with the highest metallic content of ∼47 % in a reproducible manner. Importantly, the work established that in addition to the rich metallic MoS₂ phase (1T), the electronically coupled interfaces between MoO₃ and MoS₂ nanodomains, profusion of active sites, and tuned electrical conductivity significantly contributed to hydrogen evolution reaction (HER)-catalytic activity, affording a low overpotential of 210 mV (with respect to the reversible hydrogen electrode) at a current density of 10 mA/cm², a small Tafel slope of ∼50 mV/dec, and high stability. Overall, this work demonstrated a controllable one-step hydrothermal method for the rational design and synthesis of a 3D network of MoS₂/MoO₃ nanosheets with high 1T-MoS₂ metallic yield, simultaneous incorporation of MoO₃/MoS₂ heterointerfaces, sulfur vacancies, and tuned electrical conductivity, which are highly beneficial for clean energy conversion applications that can potentially be expanded to other two-dimensional TMD materials.

The scaling-up of electrochemical CO₂ reduction requires circumventing the CO₂ loss as carbonates under alkaline conditions. Zero-gap cell configurations with a reverse-bias bipolar membrane (BPM) represent a possible solution, but the catalyst layer in direct contact with the acidic environment of a BPM usually leads to H₂ evolution dominating. Here we show that using acid-tolerant Ni molecular electrocatalysts selective (>60%) CO₂ reduction can be achieved in a zero-gap BPM device using a pure water and CO₂ feed. At a higher current density (100 mA cm^-2), CO selectivity decreases, but was still >30%, due to reversible product inhibition. This study demonstrates the importance of developing acid-tolerant catalysts for use in large-scale CO₂ reduction devices.