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.

A high-efficient oxygen evolution cocatalyst decorated on α-Fe2O3 has been considered as one of the most prospective approaches to accelerate the charge transport at the interface between photoanode and electrolyte. However, efficient charge transport from the semiconductor to the surface of the cocatalyst is still a challenge in fabricating semiconductor electrodes integrated with cocatalysts. Here, we elaborately introduce ferrihydrite (Fh) as a hole transfer channel between Ti doped α-Fe2O3 (Ti–Fe2O3) and cobalt phosphate (CoPi), which exhibits a superior photocurrent density of 3.0 mA/cm2 at 1.23 VRHE and 100 mV negative shift of the onset potential in contrast to CoPi/Ti–Fe2O3. The outstanding photoelectrochemistry performance is not only ascribed to the accelerated charge transfer from Ti–Fe2O3 to the surface of CoPi, but also beneficial from the fluent injection of photogenerated holes into the electrolyte, when Fh is introduced between Ti–Fe2O3 and CoPi. This work emphasizes the importance of introducing a hole transfer channel between semiconductor and cocatalyst in constructing outstanding photoanodes.

Nickel phosphide (NiP) was used as an excellent water oxidation cocatalyst for photoelectrochemical (PEC) water splitting, which could significantly promote the hole injection efficiency and suppress the back reaction of water oxidation over a Ti doped FeO photoanode.

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