Tailoring nickel sulfide/nickel phosphide composites derived from dppe-based Ni(II) dithiocarbamates for efficient bifunctional OER–HER electrocatalysis

• New dppe appended Ni(II)-dithiocarbamate with isomeric phenolic group synthesized and characterized. • These complexes used as precursors for nickel sulfide/phosphide composites. • The obtained composites were used as electrocatalysts for OER and HER. • The composite obtained from p-OH functionalized complex displayed best performance. • The differences in the catalytic activities were attributed to nature of phases and ECSA parameters. The high cost, limited abundance and wide industrial demand for noble metals drive the search for inexpensive and efficient non-noble metal electrocatalysts for oxygen/hydrogen evolution reactions (O/HERs) to meet global clean energy needs. Herein, three isomeric N -benzyl-1-( o/m/p -substituted hydroxyphenyl)dithiocarbamate appended Ni(II) complexes viz. [Ni(S 2 CN(CH 2 C 6 H 5 )(CH 2 C 6 H 4 - o -OH))(dppe)][PF 6 ] ( 1 ), [Ni(S 2 CN(CH 2 C 6 H 5 )(CH 2 C 6 H 4 - m -OH))(dppe)][PF 6 ] ( 2 ) and [Ni(S 2 CN(CH 2 C 6 H 5 )(CH 2 C 6 H 4 - p -OH))(dppe)][PF 6 ] ( 3 ) have been synthesized and solvothermally decomposed in oleylamine to engender nickel sulfide/phosphide composites: NiS-2BA, NiS-3BA and NiS-4BA , respectively. The compositions of the decomposed materials are identified using PXRD studies as; Ni 7 S 6 ( NiS-2BA ), Ni 7 S 6 /NiP ( NiS-3BA ) and Ni 7 S 6 /NiP/Ni 8 P 3 ( NiS-4BA ), which have further been substantiated using FESEM-EDS, HRTEM-SAED and XPS analysis. These materials showcase promising bifunctional activity for OER/HER in basic/acidic media. NiS-4BA demonstrates the best activity since it exhibits the lowest Tafel slopes and highest current densities for both OER (117 mV·dec ‑1 ; 43.2 mA·cm -2 ) and HER (136 mV·dec ‑1 ; 72.4 mA·cm -2 ) at 20 mV·s -1 . This good electrocatalytic activity arises from its small particle size, high electrochemical surface area, and synergistic multiphase composition. Overall, this study establishes that the positional isomeric phenolic –OH group on the ligand governs the phase evolution, morphology, and particle size, leading to the formation of tunable multiphase Ni 7 S 6 /NiP/Ni 8 P 3 composites with enhanced and promising bifunctional OER/HER catalytic performance. Nickel sulfide: nickel phosphide composites were synthesized via solvothermal decomposition of heteroleptic Ni(II)- dithiocarbamates and employed as electrocatalysts for oxygen and hydrogen evolution reactions.