We report a new reducing agent system: hydriodic acid with trifluoroacetic acid, which can chemically convert graphene oxide into reduced graphene oxide at temperatures below 0 °C in solution. This is the first achievement to produce reduced graphene oxide at subzero temperature with a mass production.

Surface engineering of TiO₂ is faced with the challenge of high solar-to-hydrogen conversion efficiency. Recently, surface-disordered TiO₂, referred to as black TiO₂, which can absorb both visible and near-infrared solar light, has triggered an explosion of interest in many important applications. Unfortunately, the mechanism underlying the improved photocatalytic effect from an amorphous surface layer remains unclear and seems to contradict conventional wisdom. Here, we demonstrate selectively “disorder engineered” Degussa P-25 TiO₂ nanoparticles using simple room-temperature solution processing, which maintain the unique three-phase interfaces composed of ordered white-anatase and disordered black-rutile with open structures for easy electrolyte access. The strong reducing agent in a superbase, which consists of lithium in ethylenediamine (Li-EDA), can disorder only the white-rutile phase of P-25, leaving behind blue coloured TiO₂ nanoparticles. The order/disorder/water junction created by the blue P-25 can not only efficiently internally separate electrons/holes through type-II bandgap alignment but can also induce a strong hydrogen (H₂) evolution surface reaction in the sacrificial agent containing electrolyte. As a result, the blue P-25 exhibited outstanding H₂ production rates of 13.89 mmol h⁻¹ g⁻¹ using 0.5 wt% Pt (co-catalyst) and 3.46 mmol h⁻¹ g⁻¹ without using any co-catalyst.

A new chemical dual-functional reducing agent, thiophene, was used to produce high-quality reduced graphene oxide (rGO) as a result of a chemical reduction of graphene oxide (GO) and the healing of rGO. Thiophene reduced GO by donation of electrons with acceptance of oxygen while it was converted into an intermediate oxidised polymerised thiophene that was eventually transformed into polyhydrocarbon by loss of sulphur atoms. Surprisingly, the polyhydrocarbon template helped to produce good-quality rGO_C (chemically reduced) and high-quality rGO_CT after thermal treatment. The resulting rGO_CT nanosheets did not contain any nitrogen or sulphur impurities, were highly deoxygenated and showed a healing effect. Thus the electrical properties of the as-prepared rGO_CT were superior to those of conventional hydrazine-produced rGO that require harsh reaction conditions. Our novel dual reduction and healing method with thiophene could potentially save energy and facilitate the commercial mass production of high-quality graphene.