Engineered iron-carbon-cobalt (Fe3O4@C-Co) core-shell composite with synergistic catalytic properties towards hydrogen generation via NaBH4 hydrolysis.

Cobalt (Co) nanoparticle supported catalysts have better dispersion and recyclability than unsupported Co. However, the surface chemistry and limited surface area (SA) of supports limit their Co loading which lowers activity. Currently, supports with high SA and functionality which allow high Co loading are been developed. However, a smarter solution would be to develop "active" supports which can boost the activity of Co, even at low loading. The value of such a support lies in the ability to use low catalyst loading without scarifying activity. Herein, we demonstrate how via a simple annealing process the chemical properties of Fe3O4 and physico-electrical properties of carbon (C) in Fe3O4@C can be effectively combined to prepare an "active" support for Co. The unique properties of the "active" Fe3O4@C triggers a synergistic catalytic reaction involving Co, Fe3O4 and C during NaBH4 hydrolysis. Consequently, the hydrogen generation rate (1746 ml g-1 min-1) and activation energy (47.3 kJ mol-1) of Fe3O4@C-Co are significantly enhanced compared to reported catalyst even though its Co loading is significantly lower. Additionally, Fe3O4@C-Co is highly recyclable which demonstrates its stability. Our study gives a new perspective on the role supports can play in catalyst design.