Cu5FeS4 quantum dots as a single-component photo-assisted electrocatalyst for efficient hydrogen evolution

Photo-assisted electrocatalytic (P-EC) hydrogen evolution reaction (HER) has attracted extensive attention by directly integrating the photo- and electroactive materials, exhibiting dramatically improved activity and kinetics upon light irradiation. In this work, an efficient single-component P-EC catalyst was developed by growing Cu5FeS4 quantum dots (QDs) on nickel foam (NF) in situ toward the concept approval of dual function integration in one particle. The optimized Cu5FeS4/NF catalyst displays a dramatic overpotential decrease from 118 mV to 52 mV at 10 mA cm(-2) for HER under light, exceeding that reported for all transition metal sulfides. Moreover, to reach 100 mA cm(-2), it requires an overpotential of 242 mV, superior to commercial Pt/C (256 mV). The excellent P-EC performance is attributed to the effective integration of the induced photovoltage and promoted active sites in Cu5FeS4, as observed by the photoinduced flat-band potential increase and impedance decrease. Transient photovoltage spectroscopy indicated the promoted charge extraction kinetics in Cu5FeS4 with Fe incorporation. DFT calculations confirm the decreased adsorption free energy of H* and promoted HER kinetics on Cu5FeS4 with light. This work provides an effective fabrication strategy for the synergy of photo- and electrocatalysis in one particle. Understanding the mechanism also provides an interesting inspiration for integrated photoelectrocatalysis in other more challenging fields, such as carbon dioxide and nitrogen reduction.