NOVELTY - A photocatalyst or structure (A1) comprises an electrically conductive titanium substrate having a macroporous architecture, where exposed surfaces of titanium substrate have been converted into titanium dioxide.    USE - As photocatalyst e.g. flexible high surface area photocatalyst architecture (claimed) used in microbial fuel cell (MFC) for treating water.    ADVANTAGE - The electrically conductive substrate structure is configured such that applying a potential bias to the substrate causes a boost in photocatalytic efficiency; or is configured such that applying a potential bias to the substrate within an electrolytic cell, causes electrophoretic cleaning of the surface of the photocatalyst. The process can achieve a coating having over 96% of the anatase phase, and thus providing surface area enhancements. The photocatalyst is a macroporous titanium dioxide structure. This can be formed by surface oxidation of any permeable structure that presents a titanium surface (such as a sponge woven from titanium metal wire). Thus, a high surface area of anatase can be achieved in a single, cohesive, flexible, and readily scaleable unit. The photocatalyst can consist of reinforced metal wire, which offering a flexible compliant architecture, which conforms to varied geometries. This allows the photocatalyst to be wrapped around elements such as ultraviolet (UV) radiation sources in a water purification system. The titanium oxide can be in the form of a permeable sponge structure which is used for fluid flow management in a water purification system. The electrically conductive substrate sponge structure can be used to electrically integrate the photocatalyst into an electrolytic cell. If titanium (or any other metal) wire is used as a substrate, this photocatalyst benefits from the toughness and elasticity of the metal, and is far more flexible and manageable structure for water purification applications than a powder-based photocatalyst or a more conventional porous ceramic. The intimate coupling of photocatalytic advanced oxidation with microbial activity provides a route to overcoming the limitations of microbial fuel cell (MFC) microbial metabolic activity (thus enhancing energy recovery and chemical oxygen demand (COD) reduction) and to achieving treatment (oxidation) of hazardous micropollutants. The photocatalyst can be used in a technique to allow advanced oxidation (AO) and microbial oxidation to occur within the MFC environment, and also to an improved photocatalyst structure for the advanced oxidation stage itself. Because the TiO2 photocatalyst has a very flexible architecture (compliant and reinforced by titanium wire substrate), it can be incorporated into a wide range of UV exposure systems and geometries. When applied to commercially pure grades of titanium (i.e. grades 1-4), the process also generates exceptionally high phase proportions (greater than 90 wt.%) of the anatase phase of TiO2 (titania) in this single process step. The process also generates a cohesive, erosion-resistant, and well-adhered surface oxide with good compliance (with a Young's modulus of only 15-20 GPa). All of these attributes combine to offer a practical high surface area anatase TiO2 photocatalyst for advanced oxidation which is a practical structure for applications such as water purification and electrical power production within systems such as a Graetzel cell.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a flexible high surface area photocatalyst architecture (A2) comprising a compliant, cohesive, well-adhered and highly porous surface layer of anatase phase of titanium dioxide, formed in a single step by the electrolytic oxidation of a titanium surface on a permeable, flexible, and electrically conductive substrate sponge structure; and    (2) manufacturing a photocatalyst or structure having an electrically conductive titanium substrate containing a macroporous architecture involving converting exposed surfaces of the titanium substrate into titanium dioxide.