Nickel, a non-noble metal, is one of the most promising candidates for photocatalysis because it is inexpensive and an earth-abundant metal. Herein, Ni/CM-CN nanocomposites with Ni as a cocatalyst were synthesized by a simple solvothermal method. Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed that Ni nanoparticles were loaded onto the surface of CM-CN. The prepared Ni/CM-CN nanocomposites exhibited an enhanced hydrogen evolution activity. The most active catalyst contained 10% Ni and produced H at a rate of 313.2 μmol h g, which was obviously higher than that of pure CM-CN. The results of photoluminescence (PL) and photoacoustics (PA) studies indicated that the recombination efficiency of photo-induced electron-hole pairs was decreased for CM-Ni10 as compared to that for unmodified CM-CN. The transient photovoltage (TPV) measurements directly demonstrated that the recombination time of electron-hole pairs in CM-Ni10 was prolonged. More importantly, the reversed surface photovoltage (SPV) and the declined surface photocurrent (SPC) response of CM-Ni10 revealed that the photogenerated electrons could be trapped by Ni, leading to a better separation efficiency and a superior hydrogen production. Finally, the possible mechanism is proposed to illuminate the photogenerated charge behavior between CM-CN and Ni, which might provide a theoretical basis to develop efficient cocatalysts for photocatalytic water splitting.

For semiconductor-based PEC systems, loading an appropriate cocatalyst on a semiconductor (such as a solar-active material) can significantly improve the PEC activity due to the suppression of photogenerated charge recombination. But there is little direct information about the role of a cocatalyst in the spatial separation of photogenerated charge carriers. In our work, a combination of surface photovoltage spectroscopy (SPS), transient photovoltage (TPV) technique, photoelectrochemical impedance spectroscopy (PEIS) and transient photocurrent measurements was used to study the real role of Ni(OH)2 as a cocatalyst for the enhanced PEC performance of Ni(OH)2-modified Ti-doped α-Fe2O3. It was found that Ni(OH)2 as a hole storage layer enhances the separation of photogenerated charge carriers and increases the lifetime of holes, which contributed to the enhanced photocurrent. In addition, Ni(OH)2 is a good cocatalyst for urea oxidation which suppresses the over-potential, resulting in a negative shift of the onset potential.

The influence of interface charge transfer between the semiconductor and cocatalyst has rarely been addressed. The concept of construction of a metallic charge transfer channel could be employed as a general strategy for photoconversion applications.

High‐quality nanocrystals (NCs) are vital to achieve high‐performance polymer/nanocrystals hybrid solar cells (HSCs). However, in‐depth investigation on aqueous CdTe NCs related properties is extraordinarily insufficient, thus, limiting the further improvement of the device performance of aqueous‐processed HSCs. In this work, the effects of chlorine (Cl) on the synthesis of aqueous CdTe NCs, crystal growth, defect passivation, photocarrier dynamics, and device performance are systematically investigated. We demonstrate that the surface trap states of as‐prepared aqueous CdTe NCs can be effectively passivated by introducing Cl ions in the synthetic process. In addition, it is discovered that Cl in the as‐prepared CdTe NCs can promote CdTe grain growth in the sintered process to reduce grain boundaries. The aqueous‐processed poly(p‐phenylenevinylene) (PPV)/CdTe HSCs are used as prototype solar cells to systematically study the influence of Cl on the electrical properties of CdTe NCs. The power conversion efficiency (PCE) of the HSCs based on CdTe NCs with optimal Cl content is improved by a factor of 25 compared to that based on the CdTe NCs without Cl. The ultrafast transient absorption (TA), transient photovoltage (TPV) and light intensity dependent open circuit voltage (Voc) and short‐circuit current density (Jsc) measurements are implemented to systematically investigate the influence of Cl on photocarrier dynamics, including charge transfer, lifetime, and carrier recombination. The researches on carrier recombination indicate that the presence of Cl can effectively reduce nongeminate recombination to improve charge extraction efficiency, thus leading to elevated device performance. Furthermore, it is demonstrated that the residual Cl after annealing also plays important roles in the highly efficient polymer/CdTe HSCs by passivating the trap states on the grain boundaries of CdTe NCs. Finally, this work suggests that the photovoltaic performance of HSCs can be further promoted through adopting improved passivation methods to reduce trap states on the grain boundaries in the future work.