*CO2 Reduction Characteristics of Cu/TiO2 with Various Reductants DOI: http://dx.doi.org/10.5772/intechopen.93105*

[32] Qin S, Xin F, Liu Y, Yin X, Ma W. Photocatalytic reduction of CO2 in methanol to methyl formate over CuO-TiO2 composite catalysts. Journal of Colloid and Interface Science. 2011;**356**: 257-261

[33] Liu L, Gao F, Zhao H, Li Y. Tailoring Cu valence and oxygen vacancy in Cu/ TiO2 catalysts for enhanced CO2 photoreduction efficiency. Applied Catalysis B: Environmental. 2013; **134-135**:349-358

[34] EELS data base [Internet]. 2020. Available from: https//eesdb.eu/spec tra/titanium-dioxide-2/ [Accessed: 18 March 2020]

[35] Hinojosa-Reyes M, Camposeco-Solis R, Zanella R, Zanella R, Gonzalez VR. Hydrogen production by tailoring the brookite and Cu2O ratio of sol-gel Cu-TiO2 photocatalysts. Chemosphere. 2017;**184**:992-1002

[36] Nishimura A, Zhao X, Hayakawa T, Ishida N, Hirota M, Hu E. Impact of overlapping Fe/TiO2 prepared by sol-gel and dip-coating process on CO2 reduction. International Journal of Photoenergy. 2016;**2016**. DOI: 10.1155/ 2016/2392581

[37] Nishimura A, Komatsu N, Mitsui G, Hirota M, Hu E. CO2 reforming into fuel using TiO2 photocatalyst and gas separation membrane. Catalysis Today. 2009;**148**:341-349

[38] Nishimura A, Okano Y, Hirota M, Hu E. Effect of preparation condition of TiO2 film and experimental condition on CO2 reduction performance of TiO2 photocatalyst membrane reactor. International Journal of Photoenergy. 2011;**2011**. DOI: 10.1155/2011/305650

[39] Paulino PN, Salim VMM, Resende NS. Zn-Cu promoted TiO2 photocatalyst for CO2 reduction with H2O under UV light. Applied Catalysis B: Environmental. 2016;**185**:362-370

[40] Tahir M, Amin NAS. Photo-induced CO2 reduction by hydrogen for selective CO evolution in dynamic monolith photoreactor loaded with Ag-modified TiO2 nanocatalyst. International Journal of Hydrogen Energy. 2017;**42**: 15507-15522

[41] Ambrus Z, Balazs N, Alapi T, Wittmann G, Sipos P, Dombi A, et al. Synthesis, structure and photocatalytic properties of Fe(III)-doped TiO2 prepared from TiCl3. Applied Catalysis B: Environmental. 2008;**81**:27-37

[42] Navio JA, Colon G, Litter MI, Bianco GN. Synthesis, characterization and photocatalytic properties of irondoped titania semiconductors prepared from TiO2 and iron (III) acetylacetonate. Journal of Molecular Catalysis A: Chemical. 1996;**106**:267-276

[43] Song G, Xin F, Chen J, Yin X. Photocatalytic reduction of CO2 in cycohexanol on CdeS-TiO2 heterostructured photocatalsyt. Applied Catalysis A: General. 2014;**473**:90-95

[44] Aguirre ME, Zhou R, Engene AJ, Guzman MI, Grela MA. Cu2O/TiO2 heterostructures for CO2 reduction through a direct Z-scheme: Protecting Cu2O from photocorrosion. Applied Catalysis B: Environmental. 2017;**217**: 485-493

[45] Ambrozova N, Reli M, Sihor M, Kustrowski P, Wu JCS, Koci K. Copper and platinum doped titania for photocatalytic reduction of carbon dioxide. Applied Surface Science. 2018; **430**:475-487

**Chapter 5**

(HER)

**Abstract**

**1. Introduction**

**97**

*and Satyen Saha*

Recent Progress of Electrocatalysts

and Photocatalysts Bearing First

Hydrogen Evolution Reaction

*Shipra Sagar, Ravi K. Kanaparthi, Manish K. Tiwari*

fundamental design principle and structural properties relationship of electrocatalysts and photocatalysts. Finally, we discuss some challenges and

**Keywords:** redox-active-ligand, first-row transition metals, hydrogen evolution,

Climate change and increasing energy demand have emphasized research on sustainable energy source [1, 2]. Day-by-day increase of human population and global requirements has compelled researchers to develop new renewable sustainable energy sources in replacement of hydrocarbon deposits [3]. Renewable sources such as solar power, wind, and water, storage of these energies for on-demand utilization, and transportation are the major challenges for researchers. To develop a clean and eco-friendly environment, splitting of water into hydrogen and oxygen is a tremendous way to produce sustainable energy. Hydrogen gas emerged as a green energy fuel due to its high-energy density and zero carbon dioxide (CO2) emission [4–6]. In this regard, electrocatalytic and photocatalytic H2 generation

opportunities of research in the near future in this promising area.

catalytic cycle, electrocatalyst, photocatalyst

The design and modification of metal–organic complexes for hydrogen (H2) gas production by water splitting have been intensively investigated over the recent decades. In most reported mechanistic pathways, metal hydride species are considered as crucial intermediates for H2 formation where the metal present at the active site plays an imperative role in the transfer of electron and proton. In the last few decades, much consideration has been done on the development of non-precious metal–organic catalysts that use solar energy to split water into hydrogen (H2) and oxygen (O2) as alternative fossil fuels. This review discussed the design, fabrication, and evaluation of the catalysts for electrocatalytic and photocatalytic hydrogen production. Mechanistic approach is addressed here in order to understand the

Row Transition Metal for
