Achievements and Trends in Photoelectrocatalysis: from Environmental to Energy Applications

Abstract

The great versatility of semiconductor materials and the possibility of generation of electrons, holes, hydroxyl radicals, and/or superoxide radicals have increased the applicability of photoelectrocatalysis dramatically in the contemporary world. Photoelectrocatalysis takes advantage of the heterogeneous photocatalytic process by applying a biased potential on a photoelectrode in which the catalyst is supported. This configuration allows more effectiveness of the separation of photogenerated charges due to light irradiation with energy being higher compared to that of the band gap energy of the semiconductor, which thereby leads to an increase in the lifetime of the electron-hole pairs. This work presents a compiled and critical review of photoelectrocatalysis, trends and future prospects of the technique applied in environmental protection studies, hydrogen generation, and water disinfection. Special attention will be focused on the applications of TiO 2 and the production of nanometric morphologies with a great improvement in the photocatalyst properties useful for the degradation of organic pollutants, the reduction of inorganic contaminants, the conversion of CO 2 , microorganism inactivation, and water splitting for hydrogen generation.

Low Temperature Synthesis of Nest-Like Microsphere with Exposed (001) Facets and Its Enhanced Photocatalytic Performance by NaOH Alkalization

“…From Figure 6d, a blue-shift from 665 to 625 nm and an absorbent peak at 256 nm emerged in the spectral change of MB with irradiation on OH-S0. 5. This means that reductive conversion to leuco-MB occurs in the degradation path of MB.…”

“…Since Fujishima discovered that titanium oxide (TiO 2 ) could split water in 1972 [1], TiO 2 has been studied for its lack of toxicity, low cost and stability, which make it a promising photocatalyst for environmental remediation [2][3][4] and hydrogen evolving [5]. The decreasing order of the surface energies of anatase TiO 2 has been found to be 0.90 J/m 2 for (001), 0.53 J/m 2 for (100) and 0.44 J/m 2 for (101) [6,7], so most anatase TiO 2 has a low-energy (101) surface rather than high-energy (001) facets [8][9][10][11][12][13][14][15][16].…”

Fotoeletrocatálise Em Semicondutores: Dos Princípios Básicos Até Sua Conformação À Nanoescala

“…Bessegatto et al 52 revisaram as aplicações das estruturas com diferentes morfologias nanométricas do TiO 2 para (i) a degradação de poluentes orgânicos através de reações de transferência de carga de suas lacunas (h + ) com elevado poder oxidante, diretamente com o soluto orgânico ou via reação indireta com a formação de radicais hidroxila (HO • ); (ii) redução de contaminantes inorgânicos via transferência de carga de seus elétrons com a espécie em solução; (iii) inativação de microorganismos patógenos pela reação de lacunas/ radicais hidroxila com os compostos constituintes de sua membrana plasmática, organelas e até seu DNA; (iv) produção de hidrogênio através da decomposição da água, pela simultânea redução de algumas moléculas com os elétrons fotoexcitados (H 2 O/H 2 ) e oxidação de outras com as lacunas (H 2 O/O 2 ) em fotopotencial de circuito aberto. Outro aspecto interessante revisado pelos autores é a redução do gás carbônico a espécies de forte valor comercial agregado, como hidrocarbonetos puros ou oxigenados (p. ex.…”

“…A compreensão dos diversos mecanismos envolvidos permite melhor controle dos processos fotocatalíticos, viabilizando o desenvolvimento -também no país -da inventividade nesse campo da ciência com geração de dispositivos mais avançados e competitivos frente a tecnologias existentes. Entre os exemplos dessas possibilidades estão as células solares, 52,58 novos processos oxidativos avançados para tratamento de águas, 52 purificadores de ar 56 e também diversos dispositivos analíticos com viés ambiental, exemplificados pela digestão de compostos orgânicos para determinação da concentração total de metais em amostras de água [59][60][61] e a determinação da Demanda Química de Oxigênio.…”

Assessment of molecularly imprinted polymers (MIPs) in the preconcentration of disperse red 73 dye prior to photoelectrocatalytic treatment

“…The choice of a suitable photocatalyst is crucially important in photoelectrocata lysis. TiO 2 is the most widely used photocatalyst, due to its availability, low cost, and non-toxicity, as well as the fact that it has sufficient valence band potential for the oxidation of H 2 O/OH − to hydroxyl radicals ( • OH) (Bessegato et al 2015). TiO 2 nanotube array electrodes have been demonstrated to be the most appropriate morphology, because their precise structural orientation provides excellent electron percolation pathways for vectorial charge transfer, which reduces electron/hole recombination (Grimes and Mor 2009;Liu et al 2012).…”